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| Classification of weeds with examples |
Classification of weeds with examples
A. According to origin:
1. Alien (foreign in origin): Argemone mexicana (Shialkata – Mexico), Eichhornia crassipes (Kachuripana – Germany).
2. Apophytes (Indigenous to a country – Bangladesh): Oryza sativa var. Fafua (Wild rice/ Shora dhan), Saccharum spontaneum (Kash).
B. According to growing season:
1. Kharif Weeds: Those which complete most of their life cycle in kharif season (April – September). Eg. Aeschynomene aspera(Bhat shola), Digitaria ischaemum (Khudey anguli ghash), Fimbristylis miliaceae (Joina), Cyperus difformis (Sabuj nakfuli), Digitaria sanguinalis (Anguli ghash), Lichinodloa sp. (Shama).
2. Rabi Weeds: Those which complete most of their life cycle in rabi season (October – March). Eg. Chenopodium album(Bathua), Vicia stiva (Ban masur), Brassica kaber (Ban shorisha), Amaranthus viridis (Katanotey), Amaranthus spinosus (Shaknotey).
C. According to life spam:
1. Annual Weeds: Annual weeds complete their life cycle in a year or less. They propagate by seeds. Normally, they are considered easy to control. Eg. Chenopodium album (Bothua), Eleusine indica(Chapra).
2. Biennial weeds: Biennial weeds compete their life cycle in two years, first year vegetative growth and second year flowering and set seeds. Only a few troublesome weeds fall in this group. Eg. Wild carrot (Daucus carrota), Sweet clover, Bull thistle, Common mullein and common burdock.
3. Perennial weeds: Those weeds complete their life cycle more than two years. They are propagated by weeds, rhizoms, bulbs, stolons etc. Eg. Cynodon dactylon (Durba), Cyperus rotundus(Mutha), Imperata cylindrical (Ulu). They are of following types –
a. Simple perennials: Reproduced mostly by seeds. Eg. Ipomoea carnea, Lentana camara
b. Bulbous perennial: Propagate through underground parts like bulbs, bulbils and tubers. Eg. Allium canadense (Wild onion)
c. Creeping perennials: Reproduce by creeping root, rhizoms, stolons etc. Eg. Cyperus rotundus, Durba.
D. According to habitat:
1. Terrestrial Weeds: Weeds which grow in land only. Eg. Durba, Mutha, Chapra, Bothua etc.
2. Aquatic/water weeds: weeds which grow in water. Eg. Kachuripana (Eichornia crassipes).
a. Submerged weed: Weeds which grow under the water. Eg. Hydilla, Verticillata.
b. Emerged weeds: Weeds which roots are anchored in soil under water but some parts of it above the water. Eg. Sagittaria sagittafolia (Shaluk)
c. Floating weeds: Weeds which float above the water having no connection with any part of it with the soil. Eg. Kachuripana, Topapana etc.
· Free floating: Topapana (Pistia stratiotes)
· Rooted floating: Shaluk
d. Marginal weeds: Weeds germinate at the bank of the water body but creeps above the water surface. Eg. Kalmilata, Helencha, Malancha etc.
E. According to the human attitude/economic utility/economic value:
1. Absolute weeds: Weeds which are considered as weed whenever they grow. Eg. Durba, Mutha, Shama etc.
2. Relative weed: A relative weed actually a crop plant growing in mother crop field. Eg. Aus rice in Jute field and vice versa.
F. According to plant morphology/leaf shape/leaf character:
1. Narrow leaf:
a. Grasses: Grasses are the member of family Poaceae or Gramineae. They are monocotyledonous weeds. Stem are hollow, simple, prostrate and straight. Leaves are simple, alternate, venation parallel. Eg. Cynodon dactylon, Elusine indica, Imperata cylindrica.
b. Sedges: Sedges are the member of family Cyperaceae. Stem are triangular or round, hollow, leaves are straight. Eg. Cyperus rotundus, C. esculentus
2. Broad leaf:
Broad leaf weeds are dicotyledonous plants. Leaf may be compound or simple. Venation reticulate. Eg. Chenopodium album, Xanthium italicum (Ghagra)
G. According to reaction:
1. Acid soil weeds
2. Alkaline soil weed; Eg. Dandalin
H. According to degree of harm:
1. General weed: Those which are less harmful, easy to control, produced less number of seeds.
2. Noxious weeds: Those which are troublesome, produce more seeds, difficult to control and spread easily. Noxious weeds are sometimes referred to as special problem weeds.
I. According to association with human being:
1. Facultative weeds: Weeds which primarily grown in wild communities but after escape to cultivate field associating themselves closely with human affair. Eg. Opuntia spp.,
2. Obligate weeds: Weeds which grow only in cultivated field associated themselves closely with human affair. Eg. Shama, Bothua.
J. According to Growth habitat:
1. Herb: Cynodon dactylon, Cyperus rotundus
2. Shrub: Datura stramonium, Polygonum hydropiper (Bishkatali)
3. Trees: Ficus bengalensis, F. religiosa
K. According to dependence on other hosts:
1. Total parasitic: Cuscuta reflexa (Dodder)
2. Semi – parasitic: Orobanceae indica
3. Independent: Cyperus rotundus.
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