WEEDS AND WEEDS

CLASSIFICATIONBy

WEEDS SPECIES There are over 30,000 species of weeds

round the world. Out of these about 18,000 are known to cause serious losses. In the list of world’s worst weeds nutsadge (Cyperus rotundus) ranks first and hariali (Cynodon dactylon) second position.

WEEDS SPECIES The weeds with similar morphological

characters, life cycle, requirements of soil , water, climatic condition etc are grouped together as a class or category. Therefore classification of weeds is helpful for adopting weed management methods for particular group of weeds instead of against an individual weed species. It is always economical and practically feasible to manage the group of weeds as compared to manage the individual weed species.

WHAT MAKES A PLANT, A WEED?Long seed life in the soilQuick emergence Rapid early growth No special environmental requirements

for germination Ability to survive and prosper under

disturbed conditions

WEEDS CLASSIFICATION I) Classification of Weeds based on life

span:Depending upon their life cycle weeds can be

classified as1) Annual Weeds:

They complete their life cycle within one year or one season.

a) Kharif Annuals / Kharif Weeds:They appear with the onset of monsoon (June,

July) and complete their life cycle when rainy season is over (Oct or Nov) E.g Cock’s comb, dudhi, math, chimanchara , parthenium etc.

WEEDS CLASSIFICATION b) Rabi Annuals / Winter Weeds: They complete their life cycle during winter season (

Oct/Nov to Feb) E.g Vasanvel ( Chenopodium album) , Ghol ( Portulaca oleracea), wild oat etc.

c) Summer Annuals / Summer Weeds: They complete their life cycle during summer

season ( Feb to May), Majority of the Kharif seaosn weeds grow during summer season in irrigated farming E. g Parthenium , Amaranthus spp. Euphorbia Spp. ( Dudhi) etc.

d) Ephemerals: The short- lived annual weeds are called

ephemerals E. g Niruri ( Phyllanthus niruri). These weed completes its life cycle within a very short period of 2 to 4 weeks.

WEEDS CLASSIFICATION 2) Biennial Weeds:They take at least two years or two seasons

to complete their life cycle. They complete their vegetative growth in first year or season and produce flowers and seeds in the next year or season. E.g Wild carrot- ( Daucas carota), wild onion – ( Asphodelus spp) , Jangli gobhi- (Launea spp).

3) Perennial Weeds:They continue or grow for more than two

years or several years. Perennial weeds are further classified as.

WEEDS CLASSIFICATIONII) According to Root System:Depending upon the depth of root system perennial weeds

are classified asa) Shallow Rooted Perennials:Those perennial weeds having about 20 to 30 cm deep root

system are called shallow rooted perennial weeds.E. g Hariali ( Cynodon dactylon), Quack grass ( Agrophyron

repens).b) Deep Rooted Perennials:Weeds having about one meter or more deeproot system. E.g

Nutgrass ( Cyperus rotundus), Johnson grass ( Sorghum holepense ), Acacia spp. wild ber etc.  

C) Creeping Perennial Perennial weeds with vegetative structures (stolons or

rhizomes) that permit them to reproduce asexually (without seed). field bindweed, quackgrass, Canada thistle

WEEDS CLASSIFICATION III) According to Mode of Reproduction:a) Simple Perennials: Reproduce mostly by seeds.E. g Ghaneri- Lantana camara)  Acacia- ( Acacia spp),

Wild Ber- ( Zizyphus spp).b) Bulbous Perennials:Propagate by underground parts like bulbs, rhizomes ,

tubers etc, as well as seeds.E .g Cattail ( Pan kanis) (Typha spp),

Nut grass or Nut sedge ( Cyperus rotundus),Johnson grass (Sorghum halepense).

c) Creeping Perennials:Spread by lateral extension of the creeping above ground

stem or roots or by seeds.E .g Hariali – (Cynodon dactylon), Ambooshi – ( Oxalis litifolia)

WEEDS CLASSIFICATIONIV) According to the Place of Occurrence (Habitat): Depending upon the place of their occurrence they can

be grouped as under:1) Weeds of cropped lands: E. g Chandvel, Striga, Orobanche, Wild rice etc.2) Weeds of Pastures and grazing lands: E. g Parthenium, Hulhul (Cleome viscose).3) Weeds along water channel: E .g Jalkumbhi ( Eichhornia crassipes) Pandhari Phuli ( Lagasca mollis).

4.Weeds of waste places : Corners of fields, margins of channels etc., where weeds grow in profusion. Eg. Gynandropsis pentaphylla, Calotropis gigantea

5. Weeds of playgrounds, road-sides: They are usually hardy, prostrate perennials, capable of withstanding any amount of trampling. Eg. Alternanthera echinata, Tribulus terestris

WEEDS CLASSIFICATION V) According to Nature of Stem:1) Woody Weeds: These are the woody and semi-woody and

semi-woody rough stem shrubs and are collectively called brush weeds, E .g Acacia wild ber, Ghaneri (Lantana Camara) etc.

2) Herbaceous Weeds:These weeds have green and succulent

stem and common accurence on farm lands. E.g  Math, Cocks, Comb, Dudhi, Parthenium etc.

WEEDS CLASSIFICATION VI) According to the Origin of Weeds:1) Introduced or Exotic weeds/ Allien Weeds or AnthrophytesMany weeds move from the place of their origin by seeds or other

parts to a new area and establish there and become introduces weeds such introduced weeds are called alien weeds or anthrophyes.

E  .g 1. Parthenium hysterophorus –From U.S.A2. Solanum elaegnifolium- With food grain.3. Lantana camera ( Ghaneri) : From Shri-Lanka by birds.4. Cockleber / Gokhru (Xanthium strumarium) : Native of America.5. Orobanche spp. ( Bambakhu)- Europe.6. Nutgrass ( Cyperus rotundus) chandvel: Eurasia.7. Water hyacinth – Tropical America ( Introduced in India by Portuguese)8. Johnson grass- Asia and southern Europe.

2) Indigenous Weeds:Origin of majority of tropical weeds is India E .g Cock’s comb, Dudhi,

Aghada, Hariali etc.

WEEDS CLASSIFICATION VII) Facultative Weeds or Apophytes:Weeds which grow primarily in

undistributed or close communities but may some times escape to the cultivated fields, It is also called Apophytes E .g Cactus.

WEEDS CLASSIFICATION VIII) Obligate Weeds:Weeds which grow or occur primarily in

cultivated field where the land is distributed frequently. E.g Chandvel ( Convolvulus arvensis).

WEEDS CLASSIFICATION IX) Noxious Weeds: 

The weeds which are undesirable , troublesome and difficult to control are called noxious weeds E.g Nutgrass, Hariali, Parthenium , Striga, Orobanche, Water hyacinth etc.

WEEDS CLASSIFICATION X) Objectionable Weeds:Weeds which produce seeds that are

difficult to separate once mixed with crop seeds are called objectionable weeds. E. g The mixture of Argemone Mexicana (Pivala Dhotra) seeds in mustard. Wild onion in cultivated onion

WEEDS CLASSIFICATION XI) Industrials Weeds:Weeds invading areas around buildings,

highway, railway lines, fence rows, electric and telephone pole bases etc are called industrial weeds. E .g Parthenium, Reshimkata, Katemath, etc.

WEEDS CLASSIFICATION XII) Poisonous Weeds:E.g. Parthenium, Datura, Poison, ivy

( Rhus sp), etc.

CLASSIFICATION OF WEEDS Classification according to nature of

stem: Depending upon the development of bark tissues on their stems and branches, weed can be classified as :

    (a). Woody e.g Lantana(b). Semi-woody and c. Herbaceous

species.

CLASSIFICATION OF WEEDS Classification according to

association : It is classified into three classes:

(a). Season bound,(b). Crop bound,(c). Crop associated.

CLASSIFICATION OF WEEDS Classification according to

situation: Depending upon their occurrences there can be nine important groups of weeds.

             (a)   Crop-land weeds.           (b)   Falloland weeds.           (c)   Grassland or pasture weeds.           (d)   Non-cropland weeds           (e)   Aquatic weeds           (f)    Forest and woodland woods           (g)   Lawn and garden weeds.           (h)   Weeds of plantations.           (i)    Orchard and vineyard weeds

CLASSIFICATION OF WEEDS Classification according to soil:Of the several variable of soil, soil pH is

implicated most frequently with the distribution of weed species. Weeds, such as red sorrel, corn sporry and bracken tend to comminute with weed flora on saline and alkali soils.

CLASSIFICATION OF WEEDS Classification according to

climate: Temperature, rainfall, air quality, humidity and solar energy have pronounced effect on the distribution of weeds. One could classify weeds as hillside weeds, weeds of plains, temperate weeds, tropical weeds,etc.

CLASSIFICATION OF WEEDS Facultative and obligate

weed: Facultative weeds are those weeds that grow primarily in wild communities but often escape to cultivated fields. E.g. Opuntia Spp. Obligate weeds on the contrary, occur only in cultivated or otherwise disturbed land. For e.g.: Field bind weed.

CLASSIFICATION OF WEEDS Based on ecological affinities Wetland weeds They are tender annuals with

semi-aquatic habit. They can thrive as well under waterlogged and in partially dry condition. Propagation is chiefly by seed. Eg. Ammania baccifera, Eclipta alba

Garden land weeds (Irrigated lands) These weeds neither require large quantities of water like wetland weeds nor can they successfully withstand extreme drought as dryland weeds. Eg.Trianthema portulacastrum, Digera arvensis

CLASSIFICATION OF WEEDS C.Dry lands weeds These are usually

hardy plants with deep root system. They are adapted to withstand drought on account of mucilaginous nature of the stem and hairiness. Eg. Tribulus terrestris, Argemone mexicana

CLASSIFICATION OF WEEDS Based on soil pH Based on pH of the soil

the weeds can be classified into three categories. (a) Acidophile – Acid soil weeds eg. Rumex acetosella (b) Basophile – Saline & alkaline soil weeds eg. Taraxacum sp. (c) Neutrophile – Weeds of neutral soils eg Acalypha indica

CLASSIFICATION OF WEEDS Based on morphology Based on the morphology of the

plant, the weeds are also classified in to three categories. This is the most widely used classification by the weed scientists. (a) Grasses: All the weeds come under the family Poaceae are called as grasses which are characteristically having long narrow spiny leaves. The examples are Echinocloa colonum, Cynodon dactylon. (b) Sedges: The weeds belonging to the family Cyperaceae come under this group. The leaves are mostly from the base having modified stem with or without tubers. The examples are Cyperus rotundus, Fimbrystylis miliaceae. (c) Broad leaved weeds: This is the major group of weeds as all other family weeds come under this except that is discussed earlier. All dicotyledon weeds are broad leaved weeds. The examples are Flavaria australacica, Digera arvensis, Tridax procumbens

CLASSIFICATION OF WEEDS Parasitic weeds The parasite weeds are either total or

partial which means, the weeds that depend completely on the host plant are termed as total parasites while the weeds that partially depend on host plant for minerals and capable of preparing its food from the green leaves are called as partial parasites. Those parasites which attack roots are termed as root parasites and those which attack shoot of other plants are called as stem parasites. The typical examples are; 1. Total root parasite – Orabanche cernua on Tobacco 2. Partial root parasite - Striga lutea on sugarcane and sorghum

Total stem parasite - Cuscuta chinensis on leucerne and onion 4. Partial stem parasite - Loranthus longiflorus on mango and other trees.

CLASSIFICATION OF WEEDS Aquatic weeds: Unwanted plants, which

grow in water and complete at least a part of their life cycle in water are called as aquatic weeds. They are further grouped into four categories as submersed, emersed, marginal and floating weeds. 1. Submersed weeds: These weeds are mostly vascular plants that produce all or most of their vegetative growth beneath the water surface, having true roots, stems and leaves. Eg. Utricularia stellaris, Ceratophyllum demersum

CLASSIFICATION OF WEEDS 2. Emersed weeds: These plants are

rooted in the bottom mud, with aerial stems and leaves at or above the water surface. The leaves are broad in many plants and sometimes like grasses. These leaves do not rise and fall with water level as in the case of floating weeds. Eg. Nelumbium speciosum, Jussieua repens.

CLASSIFICATION OF WEEDS 3. Marginal weeds: Most of these plants

are emersed weeds that can grow in moist shoreline areas with a depth of 60 to 90 cm water. These weeds vary in size, shape and habitat. The important genera that comes under this group are; Typha, Polygonum, Cephalanthus, Scirpus, etc

CLASSIFICATION OF WEEDS . Floating weeds: These weeds have

leaves that float on the water surface either singly or in cluster. Some weeds are free floating and some rooted at the mud bottom and the leaves rise and fall as the water level increases or decreases. Eg. Eichhornia crassipes, Pistia stratiotes, Salvinia, Nymphaea pubescens.