Classification of Weeds
There are many ways on which weeds can be classified into groups for convenience of planning,interpreting and recording control measures against them. Some important classification of weeds used by weed researchers in world for different purposes are as follows:
Classification according to anatomy of weeds: Depending upon their cycle, weeds can be classified as
i. Annual weeds:
Annual weeds more commonly complete their life cycle in one season. An annual weeds can be either
a. Summer annuals
b. Kharif annuals e.g. foxtail
c. Winter annual e.g. lambs quarter
ii. Biennial weeds: Biennial weeds complete their life cycle in two years in the first year they remain vegetative, and in the second year they produce flowers and set seeds. E.g. Daucus, Carota, Nulicaulis, etc.
iii. Perennial weeds: Perennial weeds grow for three or more years. E.g. Shallow rooted perennials – Bermuda grass, Quack grass. Deep rooted perennials :Johnson grass
Classification according to cotyledenous character:
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 according to association : It is classified into three classes:
(a). Season bound,
(b). Crop bound,
(c). Crop associated.
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 according to origin of weeds:
Many of weeds in India originated in some other part of the world. For e.g. Convolvulus sp –Eurasia, cyperus –Euphorbia,-Europe, Lantana –Africa.
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 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.
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.
Noxious weeds: Noxious weeds is a plant arbitrarily defined as being especially undesirable troublesome and difficult to control for e.g. Chicory, thistle, bermuda grass (hariyali)
Submitted by Himal Jasani on Thu, 02/07/2009 - 12:47