eChapters

Garden Features

In order to break the monotony and to enhance the beauty, any garden should contain components of varying nature. Some features are not only essential but also an important part of the visual design. Besides this, any garden feature allows to discover and save the creative ideas on a wide sheet of natural green carpet. Following are important features.

1. Arbour

It is a recessed or somewhat enclosed area shaded by trees or shrubs that serves as a resting place in a wooded area. In a more formal garden, an arbour is a small structure with vines trained over lattice work on a frame, providing a shady place. A true arbour includes a bench sheltered underneath for seating, which distinguishes it from a trellis. There are different types of arbours such as archway, wood, plastic, metal, etc. Arbour can be developed at several locations of the garden such as entrances at the main gate, pergola area, patios area, pathway entrance, pool area, etc.

Definition: Bio-aesthetic planning is recognized as the aesthetic branch of horticulture which deals with planting of ornamental plants to create a picturesque effect.

The term bio-aesthetic planning was coined by Lancelot Hogben. Egyptians were the first to adopt this type of planning in their cities. In India, M.S. Randhava was the flag bearer of bio-aesthetic planning.

India is one of the twelve mega-biodiversity countries of the world with 46,000 plant species and 81,000 animal species described so far from 70% of the total geographical area surveyed so far. Bio-aesthetic planned city in South India is Bengaluru and in North India is Chandigarh (Punjab and Haryana).

Scope: Benefits like environmental, ecological and socio-economic realizes a greater scope of bio-aesthetic planning. Potential of plants in combating pollution has not been utilized effectively so far. In bio-aesthetics, efforts should be concentrated to maintain for the next millennium, natural landscapes which appear healthy, harmonious, diverse and unique. Thus, bio-aesthetic planning can play an important role in environmental amelioration of urban and industrial areas along with their beautification.

Concept: Man has aesthetic sense and makes efforts to create orderliness and beauty. Natural forms, colours and textures have inspired most of the human art. Fulfilling recreational needs through ornamental plants and wild animals brings the idea of bio-aesthetic planning.

Definition: Ecotourism that involves traveling to relatively undisturbed natural areas with specified object of studying, admiring and/or enjoying the scenery and its wild plants and animals as well as any existing cultural aspects found in these areas.

OR A tourism which contains a visit to an ecosystem is ecotourism.

OR Ecotourism is now defined as “Responsible travel to natural areas that conserves the environment, sustains the well-being of the local people and involves interpretation and education” (TIES, 2015).

The word ecotourism has been derived from two words ‘Ecosystem’ and ‘Tourism’, together it is made Ecotourism. Green globe 21 International Ecotourism Standard has adopted Ecotourism Australia’s definition of ecotourism as “Ecologically sustainable tourism with a primary focus on experiencing natural areas that fosters environmental and cultural understanding, appreciation and conservations”.

It entails not only travelling to such ecosystems, but also helping to conserve them. It involves travel to areas of natural or ecological interest, typically under the guidance of a naturalist for the purpose of observing wildlife and learning about the environment and at the same time focusing on conservation of wildlife and environment.

Definition: Annuals are the group of plants which complete their life cycle in one season or in one year.

Annuals are commonly known as seasonal as they complete the process of life like germination, growth, flowering and seed formation in one season and finally the plant wither out. Annuals are widely used for garden decoration, cut flower and pot plants. They are frequently grown as bedding plants and in rock gardens on the sides of lily pool and in shrubberies. Annuals are planted in the winter, summer and rainy season and die in a season or within a year.

Definition: A tree is a perennial plant with an elongated stem or trunk, supporting branches and leaves in most species.

Trees are not a taxonomic group but include a variety of plant species that have independently evolved a woody trunk and branches as a way to tower above other plants to compete for sunlight. Trees tend to be long lived, living up to several hundred years.

Definition: Shrub is a woody plant with several stems/branches arising at or near the ground level from the main stem, which is perennial in nature and smaller than a tree.

Shrubs are the integral part of a garden and have immense importance in landscaping as these are used for various purposes. Shrubs produce flowers, foliage, fruits, berries and enhance beauty of garden tremendously. They are hardy in nature and require less care than other ornamental plants. Availability of a large number of species and cultivars, a wide range of variations in shape, size and growth habits, remarkable range of sizes, shape and colour of flowers and fragrance have made the shrub an important garden plant.

Definition: Climbers are woody or herbaceous plants which climb up the trees and other tall objects with the help of support of their special modified organs such as tendrils, roots, thorns, rootlets, hooks, etc.

Climbing plants are excellent examples of convergent evolution, i.e. having the same basic design that evolved repeatedly in unrelated groups. Majority of these plants are the dicotyledons but climbing plants have also evolved in monocotyledons. Examples are Vanilla orchid (Orchidaceae), Greenbriars, Smilax (Smilacaceae), Gloriosa (Colchicaceae), Semele androgyna (Ruscaceae), Dichelostemma volubile (Alliaceae), Asparagus (Asparagaceae), Bowiea volubilis (Hyacinthaceae), Chusquea (Poaceae).

These are the plants that grow mainly for its ornamental or attractive leaves rather than its flowers and grown indoor or around the house. Foliage plants are often cultivated to show a variety of unique or exotic leaf shapes, textures and colours.

There is a tremendous scope in the use of these plants to beautify houses, offices, hotels, hospitals and almost all public buildings. In the modern concept and practice of indoor gardening, the scope of growing plants has been extended too many areas in and around the house including balcony, verandah, terraces and patios. These foliage plants can be displayed in different ways to bring the beauty to the surrounding. Some of the house plants can be suited well for decorating the corners of the rooms like Aglaonema, Acalypha, Croton, Dracaena, Cordyline, Dieffenbachia, etc. whereas, for enhancing window sills and boxes suitable plants are Hedera, Coleus, Euphorbia, Kalanchoe, Pilea, etc. For hanging purposes Monstera, Scindapsus are the first choice.

The wide range of climatic conditions in India provides a choice of various bulbous crops to grow them in different parts of country. The term bulbous includes a wide array of perennial plants that are grown from underground organs, including bulbs, corms, tubers and rhizomes. Any plant described as bulbous will normally have a swollen root or stem or even leaves underground. A large number of these plants producing attractive flowers are commercially grown now days. Normally bulbous plant has a three phases during a year growth, flowering and dormancy. Bulbous plants are grown commonly in beds, shrubbery, herbaceous border, grassy land and in pots and bowl. A brief description of some common bulbous crops is given below.

1. Amaryllis: Common name (CN): Belladonna lily, King or Star lily, Botanical name (BN): Amaryllis spp., Family (F): Amaryllidaceae, Origin (O): South Africa.

Amaryllis is an excellent bulbous plant with deciduous foliage. Leaves are produced after cessation of flowering. It is suitable for bedding, pot, window boxes, greenhouses, borders, etc. Flowers are sold in the market as cut flowers. The flowers are large, trumpet shaped and are borne in umbels having 3-7 florets in small flowered varieties whereas 2-4 florets of giant size in Dutch hybrids. Amaryllis is propagated by vegetative means. They are mostly propagated through bulbs. They are also commercially propagated through tissue culture. Important species are Amaryllis belladonna, A. angustifolia, A. leopolidii, A. moreliana, A. papilio, A. striata, A. miniata and A. traubii.

An unbranched evergreen tree of tropical and warm regions with a crown of very long feathered or fan-shaped leaves and typically having old leaf scars forming a regular pattern on the trunk. Palms have great ornamental value and are planted in the garden for special effects.

Palms are native of tropics and belong to Palmae or Arecaceae family. They are varied in forms, size and habit of growth. Palms do not increase in thickness and also do not show any distinction in bark wood and pith. Flowers are produced on spikes that hanged gracefully in many species. Inflorescences are highly diverse from large panicles with many orders of branching to simply spikes. Flowers may be bisexual or unisexual borne either on the same plant or on separate plant. Whereas, some palms are polygamous.

Cactus: A succulent plant with a thick fleshy stem which typically bears spines, lacks leaves and has brilliantly coloured flowers.

Succulents: Plants that have some parts that are more than normally thickened and fleshy, usually to retain water in arid climates or soil conditions.

Together cactus and succulents are important group of ornamental plants which have the ability to store water and survive in hot and dry conditions.

Definition: Ferns are flowerless plant that has feathery or leafy fronds. These are reproduced by spores released from the undersides of the fronds.

It is a member of a group of about 10,560 known extant that differ from mosses by being vascular (i.e. having water-conducting vessels). Like other vascular plants, they have branched stems and leaves.

A wide range of beautiful plants exist among ferns which are very popular worldwide. Ferns are grown for their beautiful foliage and their gracefulness. Most of the house ferns are native of tropical regions and are ideal for indoor planting, as they can grow well under shaded or semi-shaded situations. Many species of ferns are native to India. Some of them can be easily grown while others are much difficult, but can be grown well preferably under suitable growing media and proper management.

Definition: Ground covers are low growing plants which are useful for covering large areas in the landscape Or Ground cover refers to any plant that grows over an area of ground, used to provide protection from erosion and drought and to improve its aesthetic appearance. An ideal ground cover must be easily established.

Ground covers are living plants or non-living materials used to cover areas. In general, plant related ground covers have a creeping or prostrate growth habit and grow no taller than 60 cm. A good ground cover should be evergreen and provide a permanent covering. Effects that cannot be achieved with turf grass or other plantings are possible with ground covers. Ground covers provide variation in plant height, texture and colour.

Definition: A lawn is an area of land of closely mowed grasses that is primarily developed for aesthetic and recreational purpose.

A lawn is an integral part of a garden or landscape. Besides aesthetic and recreational purposes, lawn serves several other purposes. The distinguishing characteristic of turf grasses is the ability to withstand close mowing and still providing a functional, dense and healthy ground cover. Its maintenance requires little patience and care, however the final result is always worth waiting as it gives very beautiful and soothing effect to the landscape. It is also called as ‘Heart of garden’.

Lawn can be called as turf, pitch, field, sod, yard or green depending upon the plantation, usage and continent.

Definition: Bonsai is an art of growing dwarfed, ornamentally shaped trees or shrubs in shallow containers or trays. It’s an art that expresses in miniature form of a natural tree. The word Bonsai is a Japanese term which literally means “planted in a container”.

This art form is derived from an ancient Chinese horticultural practice, part of which was then redeveloped under the influence of Japanese Zen Buddhism. Thus, origin of bonsai culture is China. Though it was popularized by Japanese. The ultimate goal of growing a bonsai is to create a miniaturized but realistic representation of nature in the form of a tree. In Japan bonsai is not only a hobby but also act as status symbol.

Definition: Flower arrangement may be defined as the art of organizing and grouping together flowers and plant materials to achieve harmony of form, colour and texture.

Types of flower arrangements

A. Japanese or oriental/eastern type: Japanese flower arrangements also called ‘Ikebana’ (Ikebana, also called Kado). Emphasis is given on spiritual and religious background and only few flowers are used. “Ikenabo” was the first school of Ikebana, meaning “the arrangement of flowers of the hermitage along a pond” which was started by Buddhist monk Semmu around A.D. 621. Ikebana was practiced by Buddhist monks as a concentration exercise (Dhyana). There are three basic lines that were followed in Ikebana namely, Shin meaning heaven is generally a central vertical line of the main branch in the arrangement. Whereas, Soe meaning man is the secondary branch symbolizes human kind. Ikebana artists position Soe to grow forward from the Shin line at a right angle. Third is, Hikae, symbolizes earth is arranged at the bottom, opposite the first two elements. In India, Ikebana was introduced during sixties and gradually becomes popular.

Definition: It is an event at which flowers are displayed and judged for awards.

Flower shows help to spread the world about the joys of gardening and serve as forums for learning and discussing the latest horticultural and design trends. Such flower show offers a wide variety of helpful resources for those interested in learning more about growing flowers for exhibition, designing floral arrangements or exhibiting plants. In addition, many national level flower shows offers training opportunities for members who are interested in becoming certified flower show judges. A Preliminary spadework has to be done to make a show successful. Success depends upon the co-operation between the exhibitor and the members of the flower show committee.

The association of flowers with mankind is evidenced since dawn of the civilization. For many centuries, flowers play an important role in each and every occasions of life and no social function is considered complete without the use of flowers. Flowers are regarded as the symbol of love, beauty and a gift of nature. In India, there is a popular saying that flowers are associated with man from birth till death.

Floriculture can be defined as a specialized branch of horticulture which deals not only with the cultivation of flowers, foliage plants, climbers, trees, shrubs, cacti, succulents, etc., but also their marketing and production of value-added products from them.

Floriculture is increasingly regarded as a viable diversification from the traditional field crops due to higher returns per unit area. Flowers play a cardinal role in human behaviour and culture, bringing tranquillity and peace of mind. From a symbol of love, flowers have transformed into an industry, generating both income as well as employment. During the past few decades, appreciation of the potential of the commercial floriculture has resulted in the blossoming of this field into a viable agri-business option. The varied agro-climatic conditions prevailing in India and wide availability of natural resources are conducive for production of a large number of flowering and ornamental crops almost throughout the year. The commercial production and marketing of flowers and floriculture products have also increased during recent years due to improved marketing and communication facilities, making availability of these throughout the country and generating a huge employment.

Introduction

Anthurium is a perennial herbaceous plant of great beauty and grown either for its showy cut flower or for attractive foliage. They are valued for their colourful long lasting spathe and spadix. It is also known as Flamingo flower or Flamingo lily. In India the cut flowers of Anthurium andreanum are cultivated for considerable length of time. Its commercial cultivation is concentrated in North-eastern states and Kerala. The anthurium is getting increasing popularity in the Indian market and therefore, most of the locally produced anthurium is sold in the domestic market against reasonable prices. Its export possibility appears very promising as the flowers are already exported to the Middle East. The development of main flower distribution center in Dubai offers important possibilities for Indian floriculture.

Introduction

Bird of Paradise is known as Strelitzia as its genus is Strelitzia. The shape of flower and its brilliant orange and blue colour it resembles bird and called bird of paradise. Due to unique appearance of the flower, it is exceptionally popular as a cut flower which appears periodically throughout the year. Commercial production of cut bloom is done in California, Hawaii, Israel, France, South Africa and Japan.

Bird of paradise occupies a place of pride in the garden and is an important choice for landscaping. It is grown in backyard and also for mass effect. Plants of strelitzia can be used in the landscape in a low growing ground cover to enhance the beauty of garden. They serve well anchoring island beds when surrounded by lower growing annuals or ground cover.

Introduction

Carnation is one of the most beautiful and commercially important flower crops. It occupies prime position in the international cut flower trade and is a good commercial cut flower for internal market as well. Carnation flower can easily withstand long distance transportation as it has an excellent keeping.

The major breakthrough in carnation flower industry was evolvement of cultivar William Sim. This cultivar was produced in 1938 to 1939 by William Sim of the USA. From this red variety there have been mutations to white, pink, orange and different variegated forms.

The first genetically modified carnation variety Moondust was released in Australia by Florigene Company. They release another transgenic variety, i.e., Moonshadow.

In India carnation is grown intensively in Nasik, Pune, Srinagar, Bangaluru, Coimbatore, Delhi and Kolkata. Places having congenial climate like Kalimpong, Simla, Solan, Kullu, Ooty, Nainital, Chaubattia, Yercaud, Kodaikanal, etc. are most suitable areas for the production of cut flowers. From Himachal Pradesh and Ooty, rooted cuttings are supplied by the growers to the different parts of the country.

Introduction

China aster is one of the most popular annual flowering plant grown throughout the world. Among annuals it ranks next to chrysanthemum and marigold. It can easily be grown in the open fields for cut and loose flowers. Cut asters last long and are used in vases and floral decoration. When asters are grown in large mass, they make very showy bedding plants and are valuable for filling up the gap in mixed herbaceous border. The dwarf types are put in front and the taller behind.

Some varieties are used as pot plants. The prominent colours of flowers are blue, violet, lavender, rose, white, etc. The commercial importance of China aster is increasing in India especially in Karnataka, Tamil Nadu, West Bengal and Maharashtra.

Genetics

China aster (Callistephus chinensis L. Nees) belongs to family Asteraceae. The genus Callistephus has only a single species i.e. C. chinensis. The ploidy level is diploid (2n = 18).

Introduction

The chrysanthemum is one of the most beautiful and perhaps the oldest flowering plant. It is commercially grown in different parts of the world. Chrysanthemum is commonly known as Guldaudi. In Dutch cut flower auction, chrysanthemum ranks second after rose. It is preferred practically due to vast range of shapes and sizes of flowers, brilliance of colour tones, long lasting floret life, diversity of height and growth habit of the plant, exceptionally hardy nature, relative ease to grow all the year round and versatility of use.

It is one of the most important traditional flowers of India mainly used as a potted plant, loose flower, cut flower and as border plant in the garden. Chrysanthemum cinerariifolium inflorescences are of considerable importance in the manufacture of pyrethrin insecticides.

Introduction

Crossandra is an important traditional flower crop of South India. The word crossandra is derived from Greek words ‘krossoi’ meaning fringe and ‘aner’ meaning male, thus word crossandra means fringed stamens. It is grown for loose flower production and commonly used in temple offering and for making Gajras and Venis to use as hair adornments. Owing to their attractive colours, light weight and good keeping quality, crossandra flowers are ideal for garland making. Steady market demand and assured and regular income have made crossandra a profitable venture for South Indian farmers.

Genetics

The genus Crossandra belongs to family Acanthaceae. The diploid chromosome number of crossandra is 2n=40. This genus consists of around 50 species of tropical plants with only a few cultivated species such as Crossandra undulaefolia, C. mucronata, C. guineensis and C. sebacaulis. Crossandra undulaefolia is an important species which is grown for commercial value across the world.

Introduction

In modern garden, dahlias are extensively used for exhibition, garden display and decoration. It can be grown in any form in the garden; in beds, in borders or even in mixed borders along with other plants. It grows well in pot also. For border purpose dwarf growing type are preferred, while in pots usually large flowering dahlias are grown. The long stemmed flowers of various forms and colours are used in flower arrangement. Dahlias make excellent cut flowers, which typically last about a week in the house and are also used in making garlands.

The tubers of dahlias contain appreciable amount of insulin and fructose and small quantities of phytin and benzoic acid which are of medicinal and nutritional value.

Introduction

Gerbera is a herbaceous flower crop with leafless stalk and daisy like flowers. It is also known as Transvaal daisy. Gerbera is a popular cut flower grown throughout the world. It is ideally suited for flower beds, borders, pots and gardens.

In California and Florida, it is grown in outdoors and is becoming increasingly popular as potted plant and bedding plant, whereas in other parts of United States it is cultivated in greenhouses. Gerbera cultivation has emerged as a very important option to progressive farmers in many parts of India, especially in Maharashtra, Karnataka, North Eastern states, U.P. and Uttarakhand.

Genetics

The genus Gerbera belongs to family Asteraceae. Gerbera comprises about 70 species, which are of African and Asiatic origin. The basic chromosome number is n=25. G. jamesonii is a diploid species with somatic chromosome number 2n=50. Among the different species, G. jamesonii is the only species under cultivation.

Introduction

Gladiolus is an important commercial flower crop and is very popular as cut flower both in domestic and international market. It is a bulbous plant. Gladiolus was introduced into cultivation towards the end of the sixteenth century. The flowers are used in flower arrangement, in bouquets and for indoor decorations. In India gladiolus is commercially grown in West Bengal, Maharashtra, Uttar Pradesh, Uttarakhand, Punjab, Haryana, Sikkim, Jammu and Kashmir, Karnataka, Gujarat, Himachal Pradesh, Tamil Nadu, Madhya Pradesh, Delhi and Rajasthan.

Genetics

Gladiolus commonly called Sword Lily belongs to family Iridaceae and subfamily Ixioideae. There are about 260 species of gladiolus. It has the basic chromosome number n=15. Most members of genus are heteroploids having very small chromosomes ranging from 2n=30 to 120 (Diploid, triploid, tetraploid, pentaploid, hexaploid, octaploid and hyperaneauploid).

Introduction

Plants are grown both as shrub and climber. Flowers and flower buds are used for making garlands and Veni and for religious offerings. Jasmine oil extracted from the flower is highly valued as it is used in manufacturing perfumes, cosmetics, creams, hair oils, soaps and shampoos.

Flowers are used in jasmine tea or herbal or black tea. As a medicinal plant, jasmine has traditionally been considered an aphrodisiac and calmative. In India, it is grown in different states especially Tamil Nadu, Karnataka, Kerala, Uttar Pradesh, Bihar and West Bengal because their flower and floral buds are in great demand.

Genetics

The genus with basic chromosome number of n=13 generally consists of forms with 2n=26. However, natural occurrence of higher ploidy was also observed in J. sambac cv. Gundumalli (2n=39), cultivated variety of J. flexile (2n=52), J. primulinum (2n=39) and J. angustifolium (2n=52).

Introduction

Lily is one of the most important ornamental bulbous flowers. It is commercially cultivated for cut flower production. The flower stems of lily are long and it has longer vase life. Lilies are very useful flowering plants which can be planted in any location as they do well in the bed or border with other perennial.

Asiatic and oriental lilies are leading cut flower group and in the international market it is dominated by the Netherlands. Oriental and Asiatic hybrid lilies are compact, with plant height of 60 to 150 cm that bears many flowers.

Introduction

Marigold is an important flower crop in India. They are extensively used for making garlands, beautification and other purposes i.e. oil extraction and therapeutic uses. Apart from these uses marigold is a widely grown plant in gardens and for pots. Marigolds are also grown commercially for extraction of carotene pigments mainly xanthophylls. The carotenoid extracted from petals are added to poultry feed for intensification of yellow colour of egg yolk. Lutein which is the major constituent of xanthophylls is used for colouring food stuffs.

Marigold plantation has been found beneficial to reduce the population of nematodes. Root-knot (Meloidogyne spp.) can be effectively managed in the field without pesticides.

Genetics

Marigold belongs to family Asteraceae. There are about 33 species of the genus Tagetes. Important species are T. erecta, T. patula, T. tenuifolia, T. lucida, T. lacera, T. lemmonii, T. minuta, T. pusilla and T. corymbosa. The chromosome number in diploid species i.e. T. erecta, T. tenuifolia, T. elongata, T. lemmonii, T. jaliscensis and T. lucida is 2n = 24, however, tetrapoid species i.e. T. patula, T. minuta, T. remotifolia, T. mendocina and T. biflora is 2n = 48.

Introduction

Orchids are the most beautiful flower and have conquered the cut flower industry all over the world. They are valued for cut flower production and as potted plant. Their beautiful flowers varied in size, shape and colour, long life of flowers on the plants and an amazingly long keeping quality which no other plant can claim.

Many of orchids are source of important secondary metabolites as given below.

Vanillin produced from Vanilla planifolia is used in flavouring industries.

Dendrobine and nobilonine from Dendrobium nobile.

Laburnine from Liparis bicallosa.

Malaxine from Malaxis congesta.

Phalaenopsine from Phalaenopsis mannii.

Introduction

The rose is one of the oldest flower in cultivation and rank 1^st position worldwide as cut flower. There are two types of roses; first stemless rose supplied by field grown roses for making garlands or extraction of rose oil or rose water. Second is stemmed rose, which is mainly grown under protected conditions for cut flower production used for making bouquets or interior decoration.

The cultivation of this flower has developed with the distillation of rose as mentioned in Ayurveda by Charaka around 100 A.D. At present, it has become the most important commercial flower. A large quantity of rose flowers is used for decoration purpose.

Introduction

Among ornamental bulbous plants, tuberose occupies a very prominent position. Tuberose flower is much adored for its prettiness, elegance and fragrance. It is commercially grown as cut flower, loose flower as well as for its potential in perfume industry.

The flowers of tuberose are used for artistic garlands, floral ornamentals, bouquets and buttonholes. The long flower spikes are excellent as cut flowers for table decoration when arranged in vases.

Plants of tuberose can be used in landscapes, in all-white gardens or with other plants. Variegated varieties with golden or yellow striped leaves are very attractive and these varieties are suitable for garden beautification. Potted plants can be put in decorative containers and used for entranceways and interiors.

Seed is defined as “Fertilized and ripened ovule, consisting of the plant embryo, varying amounts of stored food material and a protective outer seed coat”. It is one of the most vital and important inputs for increasing production of crops. Commercial flower seed production is an international business involving highly specialized growers. Demand of flower seed production increased due to recent advances in commercial production of bedding plants, plug production technology, increased area of gardening, flower growing in home gardens and cut flowers with highly viable seeds and very high percentage of uniform seedlings. It seems to have great scope for expansion in developing countries like India, especially under north Indian climate having favourable growing conditions, skilled and cheap labour.

The world germplasm contains more than 1500 different varieties of flowers and ornamental crops. Each species of flower grown for seed has its own specific time, culture, problem of pollination and harvesting and storage requirements. Growing flower from seed is an important component of commercial flower production and their uses in landscape gardening.

The association of weeds with field crops was started when ancient man started cultivating plants as crops commercially. However, type of weed flora went on shifting with the passage of time, due to changing climatic conditions, cropping pattern, agronomic practices, crop cultivars etc. When crops are cultivated invariably a variety of volunteer undesirable vegetation come up simultaneously which competes with the crop for all growth factors viz., nutrients, soil moisture light, space etc.

Definition of Weed

Weed is a plant that originates under a natural environment and in response to imposed and natural environments, evolved and continues to do so as an interfering associate with our desired plant and activities.

Weed is a plant growing out of place. They are unwanted not useful, persistent and prolific, effectively competing with the beneficial and desirable crop plants for space, nutrients, sunlight, and water, interfere with agricultural operations and thereby reducing the yield and quality of produce.

Weeds are unwanted and undeserved plants that interfere with the utilization of the land and water resources and thus adversely affect crop production and human welfare. Thus a plant out of its place or a plant growing where it is not desired is a weed. This definition was given by Buchholtz in 1967. E.g. Bajra is a weed in pulse, pulse is a weed in bajra, tomato is a weed in brinjal field. Weed is defined as the unwanted, undesirable plant growing out of their proper place which interfere with the utilization of natural resources, prolific, persistent, competitive, harmful and even poisonous in nature and can grow in adverse climatic conditions (Jethro Tull: Father of Weed Science).

Weediness: Weediness is defined as the state or condition of a field, flower beds, lawns and so forth in which there is an abundance of weeds.

Weeds are plants that are unwanted in a given situation and may be harmful, dangerous or economically detrimental. Weeds are a serious threat to primary production and biodiversity. They reduce farm and forest productivity, displace native species and contribute significantly to land and water degradation. The costs of weeds to the natural environment are also high, with weed invasion being ranked second only to habitat loss in causing biodiversity decline.

Weed Biology

Weed biology is the study of the establishment, growth, reproduction, and life cycles of weed species and weed societies/vegetation. Weed biology is an integrated science with the aim of minimizing the negative effects, as well as using and developing the positive effects, of weeds.

Life Cycle - Based on life cycle weeds are classified as annuals, biennials or perennials.

Annuals

Annuals complete their life cycle from seed in less than one year. There are two types: summer and winter annuals. Summer annuals germinate in the spring, mature, produce flowers and seeds and die before fall. Winter annuals germinate in the fall, overwinter in a seedling or rosette stage, mature, produce flowers and seeds, and die in the spring or early summer. Because of the seedling stage, annual weeds are generally easy to control. There are usually few annual weeds present in low bush blueberry fields.

Biennials

Biennials generally complete their life cycle over two years. The first year the seeds germinate and form a basal cluster of leaves and a tap root. The plant overwinters in this stage. During the second year the weed produces a flower stalk, sets seed and dies. Examples of biennial weed are evening primrose and wild carrot.

Weed Ecology

Ecology is the study of reciprocal relationship between organisms and their environments. The ecology of weed is thus concerned with growth characteristics and adaptations that enable weeds to exploit the ecological niches left open in those environments altered by man for his use and the survival mechanisms where by weeds persist in such environments. In simple words weed ecology is reciprocal relationship of weeds with their environments. Weeds grow voluntarily in all crops raised by human beings since ancient ecology of weeds is divided into two categories (types).

1. Weed Auto Ecology

It is study of only one population i.e. how an individual species in a population interacts with its environment at all stages of its life cycle. So, in case of auto ecology competition within same species (intraspecific) or with crop plants (inter specific competition) is studied.

2. Weed Synecology

The study of relationships between communities of different weed species with their environment is called weed synecology. Different weed species grow in certain combinations and in specific patterns in the ûeld. The population of different weed species interact with the external environmental conditions and among themselves. Weed communities differ from field to field and crop to crop in the same locality. The community character is dynamic and changes in form and composition of weed flora takes place in course of time due to some external and internal factors prevailing in the community. This process is called ecological succession. With the passage of time there will be series of changes in the composition of weed community which ultimately results in stable community. This is termed as climax community.

Weed monitoring is conducted to detect significant weed problems, rank them for relative severity and sort them by management type annuals, biennials, perennials, grasses and broadleaves. Weed monitoring provides information to tailor weed management efforts that reduce the impact of the weeds. The primary objective of weed survey and mapping is to accurately identify and delineate land with populations of unwanted plants. These surveys are conducted so that scientists and managers can predict those areas potentially subject to weed invasion; understand the biology of the invasion process and determine means by which weeds spread; develop, implement and evaluate weed management plans; assess the economic impact of weed invasion and increase public awareness, education and weed management efforts. Weed survey information is collected and compiled into maps showing the distribution and severity of infestation. Weed monitoring involves repetitive surveys to track weed populations over time. A standardized system of weed surveying and mapping is necessary to provide consistently reliable information that can be compared from year to year. Further, a standardized system allows weed survey data to be incorporated into a state wide weed survey database for the production of state wide noxious weed maps.

Methods of Weed Control

Prevention, eradication and control are the fundamental principles of weed control.First basic step is to prevent the infestation of a weed(s) in a locality in order to avoid their further spread. If one fails in preventing spread of weeds, eradication step must be adopted. Eradication is limited on a very small scale and adopted only when suitable methods of complete weed removal are available as eradication is cent per cent control of weeds alongwith its root system and other propagative parts. Further, if one fails in prevention and eradication techniques then different weed control methods must be strictly followed in which the objective is to bring down the weed population (with any method) to a level that economical crop yields are possible. The aim of each weed control method is to achieve reasonable good control of weeds. Following methods for controlling weeds are very common:

Preventive Methods

Try to prevent spread of weed seeds/vegetative parts with the adoption of following preventive techniques.

Integrated Method of Weed Management

Definition

1. An integrated weed management may be defined as the combination of two or more weed-control methods at low input levels to reduce weed competition in a given cropping system below the economical threshold level. It has proved to be a valuable concept in a few cases, though much is still to be done to extend it to the small farmers’ level.
2. When more than one method is employed for controlling weeds, it is termed as integrated method weed management.

FAO Definition

It is a method whereby all economically, ecologically and toxicologically justifiable methods are employed to keep the harmful organisms below the threshold level of economic damage, keeping in the foreground the conscious employment of natural limiting factors.

IWM is the rational use of direct and indirect control methods to provide cost-effective weed control. Such an approach is the most attractive alternative from agronomic, economic and ecological point of view.

Herbicide History and Development

Common salt, ash, smelter waste, and like cheap materials have been used for centuries to control weeds on roadsides, fence rows, and pathways. But Chemical weed killing was born in 1896 when Bonnet, a French grape grower, observed that the Bordeaux mixture which he used against downy mildew of grape turned the leaves of Sinapis arvensis (a weed) black. Soon it was found that copper sulphate present in the Bordeaux mixture was responsible for its weed killing effect. Further tests in France, Germany, and U.S.A. established that copper sulphate could indeed be used for selective control of broadleaf weeds in small grains; wheat, barley, and oat. Between 1896 and 1908, several other inorganic salts, as also sulphuric acid, were found selective to small grain cereals. Of these, in Europe, a 6 to 10 per cent solution of sulphuric acid continued for considerable time as a satisfactory herbicide for broadleaf weed control in cereals, but it corroded the containers and sprayers. In the U.S.A., salts like sodium chlorate, carbon bisulphide, sodium arsenite, kainite, and calcium cyanamide were developed for non-selective eradication of perennial weeds, particularly, Convolvulus arvensis ‘field bind weed’ and Cirsium arvense ‘Canada thistle‘. In Hawaii, sodium arsenite solution was found highly effective for weed control in sugarcane plantations. Between 1930 and 1940, some boron compounds, thiocyanates, dinitro phenols (DNC and DNBP), ammonium sulphate, and certain mineral salts were developed in the west for selective and non-selective weed control. DNC and DNBP wereused extensively in Europe in small grains for broadleaf weed control, even though these chemicals dyed the hands and clothes of the users to yellow colour, almost permanently. Further milestones in weed control were introduction of organic chemical, 2-methyl-4, 6-dinitrophenoll (DMOC), in 1932 and discovery of hormone type selective weed killers. Selective residual chemicals such as substituted phenyl ureas and triazines, and non-residual chemicals diquat and paraquat are more recent discoveries.

The discovery of the herbicidal activity of 2, 4-D (2, 4-dichlorophenoxyacetic acid) first synthesized in 1941, triggered the development of modern herbicide technology. 2, 4-D proved to be an outstanding herbicide.

History on Classification of Herbicides

Copper sulphate (CuSO₄) was the earliest inorganic salt used as selective herbicide for controlling dicot weeds in cereal crops during 1896 in France, Germany, and USA. Sulphuric acid (H₂SO₄) was used as herbicide in cereals during 1909. In selective killing action depends on the fact that it runs off the leaves of the cereals and scorches rough surfaces of certain seeds. Sodium chlorate (NaClO₃) under the name mort-herbs is used in France for killing deep rooted perennials. Another non-selective herbicide, ammonium sulphamate (NH₄SO₃NH₂) was introduced in 1945 as ammate for the control of woody plants. Organic herbicides are more effective and selective.

Classification of Herbicides

Classification of herbicides is modified periodically as and when new herbicides are developed. Herbicides are classiûed based on their method of use (soil and foliage applied), mode of action (systemic or translocated and non-systemic or contact herbicide) and chemical key structure (aliphatic-aromatic, dinitrophenal, etc. Some herbicide molecules contain more than one classifying key structure and they are put into the group most likely to be contributing activity.

Any approved herbicide is known by three names: common name, chemical name and trade name. Common name of herbicide is a technically accepted abbreviation of its chemical name. Chemical name reads out its full molecular structure. Trade names refer to their formulations offered by the chemical companies for the consumers.

Herbicide Application

Generally, herbicides are applied in the form of solution or granules. Of the two, spraying solutions of herbicides formulated as wettable powders, soluble powders and emulsifiable and solution concentrates is more common. When herbicides are formulated as granular or encapsulated materials, they are applied by hand or with the help of a granular applicator.

Mode of Action

The term mode of action refers to the sequence of events from absorption into plants to plant death. The mode of action of the herbicide influences how the herbicide is applied. For example, contact herbicides that disrupt cell membranes, such as acifluorfen (Blazer) or paraquat (Gramoxone Extra), need to be applied post emergence to leaf tissue in order to be effective. Seedling growth inhibitors, such as trifluralin (Treflan) and alachlor (Lasso), need to be applied to the soil to effectively control newly germinated seedlings.

To be effective, herbicides must 1) adequately contact plants; 2) be absorbed by plants; 3) move within the plants to the site of action, without being deactivated; and 4) reach toxic levels at the site of action. The application method used, whether pre-plant incorporated, pre-emergence, or postemergence, determines whether the herbicide will contact germinating seedlings, roots, shoots, or leaves of plants.

Mode of Action of Herbicides

Herbicides perform a vital role in the management of weeds. As the name indicates, herbicides are chemicals that kill or control vegetation. Although the ultimate effect of most herbicides is the same (usually death of weed), the way they control weeds is vastly different. Physiologists use the term mode of action to describe the way the herbicides affect weeds. It includes the entire sequence of events that occur from the time the weed absorbs the herbicide to the final plant response (usually death). The term mode of action is the broad term under which all aspects of herbicidal action including the mechanism of action is included, while the mechanism of action refers to only the biochemical and biophysical responses of plants that appeared to be associated with herbicidal action.

Thus, mode of action includes absorption, translocation to an active site, inhibition of a specific biochemical reaction, degradation or breakdown of the herbicide in the plant and soil and the effect of the herbicide on plant growth and physiology.

Although two herbicides may differ chemically, they may still possess the same mode of action example trifluralin (a dinitroaniles herbicide) and propanamide (an amide herbicide) are inhibitors of microtubule/spindle apparatus. Each herbicide family (class or group) has a primary site of action which may be different in its action from others example sulfonylureas herbicides are ALS or AHAS inhibitors while glyphosate and sulfosate are ESPS inhibitors. Some may have more than one site of action, but the mostinhibitory of these will be affected first. The other site(s) may be considered secondary. Fluometuron, a urea group herbicides act by inhibiting photosynthesis at photosystem II and carotenoid biosynthesis.

Herbicide Mixtures

A mixture of two or more herbicides could be more effective for controlling different weed species. In horticultural and plantation crops, weed free situation is needed during the entire year over several years. In such situations, herbicides are to be rotated to take care of all the species of weeds. A mixture of herbicides, due to chemical reaction, may enhance or reduce the efûciency of one or more compounds. Hence, knowledge of herbicides interactions is essential for efûcient use of herbicides in weed control.

Persistence of Herbicide in Soils

Most of the herbicides are applied to soil as pre-emergence for weed control under different situations. For effective weed control, herbicides must remain in soil in active and available form until their purpose is served. Larger persistence poses hazard to subsequent land use and is undesirable. The length of time that an herbicide remains active in the soil is called persistence or soil residual life. The quantity of herbicide that remains in the soil after its mission is accomplished is referred as residue. The term residue infers the continued presence of herbicide in the soil in very small quantities even though it may not be present in herbicidal quantities or available for plant absorption. Herbicide residues in soils are undesirable mainly because they may

Injure sensitive crops in a cropping system,

Be absorbed by succeeding crops and residues accumulated in unlawful amounts in the produce,

Result in building up of herbicide residues following repeated treatments that exceed their rate of dissipation, and

Inhibit growth of soil micro-organisms.

Knowledge of persistence and carry over residual effect of herbicides is essential to use them safely and effectively. Persistence of herbicides in soils pose hazard when

Highly persistence herbicides are used,

Crop failure necessitates replanting,

A susceptible crop follows a short term crop which received a persistence herbicide, and

Decomposition of the applied herbicide proceeds very slow.

Resistance

The intensive and continuous use of herbicides over the last five decades has resulted in the development and evolution of weeds resistant to the normally phytotoxic chemicals. Although herbicide resistance was reported as early as 1957 against 2, 4-D from Hawaii the first confirmed report of herbicide resistance was against triazine herbicide in common groundsel (Senecio vulgaris) was reported in l968 from U.S.A. Over the years, more than 150 weed species have been identified as having developed biotypes resistant to at least one or more herbicide classes. Resistance to at least 15 classes of herbicides have been noted. Moreover, the area of land infested with resistant weeds is increasing rapidly. Reports of evolution of newly resistant biotypes continue to emanate from all over the world, including developing countries, e.g., India, where extensive use of herbicides in grain crops began only in the late 1970s. These reports indicate that herbicide resistance problems are accelerating and, consequently, management of weeds is becoming increasingly more difficult and complex.

The phenomenon of herbicide resistance in plants, especially in weeds, is analogous to the evolution of changes that arise in insects and pathogens in response to the continuous use of insecticides and fungicides. Herbicide resistance is the result of selection for traits that allow weed species to survive specific herbicide usage, which would otherwise cause mortality. Herbicide resistance contributes a trait of resistance within the plant species to a herbicide and resistant weeds are those plant species that express the genetic variation required to evolve mechanisms to escape control. Like other crop pests (insects, pathogens, etc.) with reference to pesticides (insecticides, fungicides, etc.), herbicide-resistant weeds are the result of intensive selection pressure in weed populations.

Generally, resistance is defined as the ability of a plant species to withstand the phytotoxicity of a chemical. This is the trait normally found in crop plants, as against weeds, thus forming the basis for herbicide selectivity. Crop resistance to a herbicide is often different from the one that exists in the phenomenon of herbicide resistance in weeds.

Herbicide resistance in the context of weeds is defined as a characteristic of the weed species to withstand a herbicide dosage substantially higher than the wild type of the same plant species can withstand. It is the inherent or acquired ability to withstand the dosage of herbicide normally used for satisfactory weed control. Resistant weed populations are unharmed by a concentration of herbicide that completely kills all unselected populations. This herbicide concentration is the one that in field practice produces an effective kill.

Herbicide susceptibility represents the other end of the scale, encompassing natural variability in sensitivity to herbicides within the unselected populations. Tolerance, on the other hand, indicates reduced susceptibility (or conversely enhanced resistance) which may sometimes result from selection by herbicides. It is a response rather less than 100% survival accompanied by zero reduction in growth at herbicide concentrations, which normally give 100% Kill of susceptible biotypes. Tolerance may also be considered the natural or normal variability of response to-herbicides that exists within a species and can easily and quickly evolve.

Shifts or changes in the abundance and types of weeds within agricultural systems are common. These shifts can occur for a number of reasons and may result from cultural, mechanical, or chemical weed management strategies. The right combination of weeds and relying too heavily on any one practice is often the most common cause. Some of the concepts associated with weed species shifts are discussed below.

A weed shift is the change in the composition or relative frequencies of weeds in a weed population (all individuals of a single species in a defined area) or community (all plant populations in a defined area) in response to natural or human-made environmental changes in an agricultural system. Weed shifts occur when weed management practices do not control an entire weed community or population. Some species or biotypes are killed by (or susceptible to) the weed management practice, others are not affected by the management practice (tolerant or resistant), and still others do not encounter the management practice (dormant at application).

Those species that are not controlled can grow, reproduce, and increase in the community; resulting in a weed shift. Any cultural, physiological, biological, or chemical practice that modifies the growing environment without controlling all species equally can result in a weed shift. Weed shift may be due to introduction of new species or change in relative proportion of members of the existing community. Latter is the most common.

A. Species shift: Change in density of one or more species in field

B. Biotype shift: Change in density of biotypes within a species. These shifts often found noticed since biotypes typically are similar in appearance. Herbicide resistantbiotypes are the most frequently studied.

Weed Management

The productivity of crops much depends on intercultural and weeding operation. The efficient management practices ultimately increases the yield level. The productivity is much dependent on various attributes starting from the variety, climate including human resource management and other factors known well to the farmers. It is estimated that nearly 30-50 per cent of the crop is lost due to weed menace in the agricultural fields. The farmers use various methods of weed control like cultural, mechanical, chemical and manual means. Encompassing all these control measures is known as integrated weed management.

The possibility of the drifting of continents was first suggested by the French scholar Antonio Snider in 1858, but this was so much opposed to the scientific view then prevailing that nobody took notice of it. In 1910 F.B. Taylor of America invoked the hypothesis of horizontal displacement of continents or continental drift with a view to explaining the distribution of mountain ranges, but for various reasons the hypothesis of Taylor received scant attention. German Professor Alfred Wegener was the first to put forward this idea in the form of a theory in 1912 and published a detailed discussion of it in 1915. But an account of the First World War (1914-18) this could not attract the attention of many scientists. In 1924 an English translation of Wegener’s book was published. Since then it has attracted much attention and publicity, and a huge literature has grown around this theory.

Wegener was primarily a climatologist and the main problem he wanted to explain was the change of climates in the geological past. There are several geological evidences to show that there have been important and large scale changes in the climates of the world in the geological past. The occurrence of coal in the cool middle latitudes indicates that the climate of these regions was hot and humid in the carboniferous times and the natural vegetation was dense forest which ultimately resulted in the formation of huge coal deposits. On the other hand, in India, South Australia, Brazil or South Africa where the climate is warm today, there are evidences of cold climate and the presence of glaciers in the carboniferous period. The only conclusion that can be reached from this is that either the climatic zones have moved or if they have not, then there has been movement of the landmasses. There are several difficulties in postulating shifts in the climatic belts of the world as their geographical distribution is governed primarily by the sun. It, therefore, appears to be more probable that the landmasses have changed their position.