11 Classification of Weeds with Examples and Scientific Name: Weeds are plants that grow in an area where they are not wanted. Weeds can be classified into categories based on their life cycle, how they spread, and the damage they cause. Annual weeds complete their life cycle in one year. They are spread by seeds that are carried by the wind or water. Some annual weeds can cause a great deal of damage because they compete with crops for nutrients, water, and sunlight. Perennial weeds live for more than one year.
Classification of weeds with examples
1. According to origin:
- Alien (foreign in origin): Argemone mexicana (Shialkata – Mexico), Eichhornia crassipes (Kachuripana – Germany).
- Apophytes (Indigenous to a country – Bangladesh): Oryza sativa var. Fafua (Wild rice/ Shora dhan), Saccharum spontaneum (Kash).
2. According to the growing season:
- Kharif Weeds: Those who 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).
- Rabi Weeds: Those who 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).
3. According to life spam:
A. Annual Weeds: Annual weeds complete their life cycle in a year or less. They propagate by seeds. Normally, they are considered easy to control. E.g., Amaranth (pigweed), Milk thistle, Sorrel, Common lambsquarters, Ragweed, Chenopodium album (Bothua), Eleusine indica(Chapra).
B. Biennial weeds: Biennial weeds complete 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. E.g., Milk thistle, Wild carrot (Daucus carrota), Sweet clover, Bull thistle, Common mullein, and common burdock.
C. Perennial weeds: Those weeds complete their life cycle of more than two years. They are propagated by weeds, rhizomes, bulbs, stolons, etc. Eg. Bermuda grass, Broadleaf plantain, Creeping Charlie, Dandelion, Goldenrod, Kudzu, Leafy spurge, Poison ivy, Sorrel, St John’s wort, Sumac, Tree of heaven, Wood sorrel, Yellow nutsedge, Cynodon dactylon (Durba), Cyperus rotundus(Mutha), Imperata cylindrical (Ulu). They are of the following types –
- Simple perennials: Reproduced mostly by seeds. Eg. Ipomoea carnea, Lentana camara.
- Bulbous perennial: Propagate through underground parts like bulbs, bulbils, and tubers. Eg. Allium canadense (Wild onion).
- Creeping perennials: Reproduce by creeping root, rhizomes, stolons, etc. Eg. Cyperus rotundus, Durba.
4. According to habitat:
- Terrestrial Weeds: Weeds that grow in land only. E.g., Durba, Mutha, Chapra, Bothua, etc.
- Aquatic/water weeds: weeds that grow in water. E.g., Kachuripana (Eichornia crassipes).
- Submerged weed: Weeds that grow under the water. Eg. Hydilla, Verticillata.
- Emerged weeds: Weeds which roots are anchored in soil underwater but some parts above the water. Eg. Sagittaria sagittafolia (Shaluk).
- Floating weeds: Weeds that 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.
- Marginal weeds: Weeds germinate at the bank of the water body but creeps above the water surface. Eg. Kalmilata, Helencha, Malancha etc.
5. According to the human attitude/economic utility/economic value:
- Absolute weeds: Weeds that are considered as weeds whenever they grow. E.g., Durba, Mutha, Shama, etc.
- Relative weed: A relative weed a crop plant growing in the mother crop field. E.g., Aus rice in the Jute field and vice versa.
6. According to plant morphology/leaf shape/leaf character:
A. Narrow-leaf:
- Grasses: Grasses are the member of the family Poaceae or Gramineae. They are monocotyledonous weeds. The stem is hollow, simple, prostrate, and straight. Leaves are simple, alternate, venation parallel. Eg. Cynodon dactylon, Elusine indica, Imperata cylindrica.
- Sedges: Sedges are a member of the family Cyperaceae. The stem is triangular or round, hollow, and the leaves are straight. Eg. Cyperus rotundus, C. esculentus
B. Broadleaf: Broadleaf weeds are dicotyledonous plants. The leaf may be compound or simple. Venation reticulate. E.g., Chenopodium album, Xanthium italicum (Ghagra).
7. According to the reaction:
- Acid soil weeds
- Alkaline soil weed; Eg. Dandelion
8. According to the degree of harm:
- General weed: These weeds are less harmful, easy to control, and produce fewer seeds.
- Noxious weeds: These weeds are troublesome, produce more seeds, difficult to control, and spread easily. Noxious weeds are sometimes referred to as special problem weeds.
9. According to association with the human being:
- Facultative weeds: Weeds have primarily grown in wild communities, but they are associated closely with the human affair after the escape. E.g., Opuntia spp.,
- Obligate weeds: Weeds that grow only in the cultivated field associate themselves closely with the human affair. E.g., Shama, Bothua.
10. According to Growth habitat:
- Herb: Cynodon dactylon, Cyperus rotundus
- Shrub: Datura stramonium, Polygonum hydropiper (Bishkatali)
- Trees: Ficus bengalensis, F. religiosa
11. According to dependence on other hosts:
- Total parasitic: Cuscuta reflexa (Dodder)
- Semi – parasitic: Orobanceae indica
- Independent: Cyperus rotundus.
In conclusion, weeds are classified according to their life cycle, morphology, and habitat. There are three main life cycles of weeds- annual, biennial, and perennial. Weeds can also be classified by their morphology or physical appearance. There are three types of morphology- grasses, broadleaf plants, and vines. Finally, weeds can be classified by their habitat- terrestrial or aquatic. Knowing the different classifications of weeds is important for proper identification and treatment.
