A weed is a plant that grows in a place where it is not wanted e.g. a vegetable plant growing on a cassava plot is a weed.
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CHARACTERISTICS OF WEEDS
- HIGH PRODUCTIVE CAPACITY: Weed posses high productive capacity and are always the first to emerge and grow when necessary condition are provided. They have many seeds. For examples a single grass head may produce thousands of seeds.
- HIGH RESISTANCE CAPACITY: They are capable of withstand adverse conditions because of their tough protective seed coats e.g. seeds of some legume
- ABILITY TO REGENERATE: Some weeds are capable of regenerating and therefore very difficult to eradicate commelina species, elephant grass and spear grass are examples of weeds that possess this characteristics
- EARLY DISPERSED: Weed seeds possess various devices for dispersal. These include spines, hook, parachute of hair, wind with which they are easily be dispersed g. tridax, goat weed and des modium.
- HIGH COMPETITIVE AND AGGRESSIVE GROWTH HABIT: Weed possess highly competitive growth habit and can easily smother crop for example spear grass, elephant grass can easily over run a farm if not regularly checked.
USES OF WEEDS
- FOOD: Some weeds are used as food for man e.g. African spinach (Amarathus coudatus) cochurs olitoris e.t.c
- ANIMAL FEEDS: Some weeds are used as food for feeding farm animals e.g. guinea grass, sedge and elephant grass
- MEDICINE: Most weeds are medicine. Drug can be extracted from such weeds e.g. lemon grass.
- EROSION CONTROL: Weeds are used for control tiny erosion e.g. Bahama grass.
- SOURCE OF ORNAMENTAL: Weeds are the major source of ornamental crops e.g. e.g. pride of Barbados, carno lily, rose, croton and hibiscus.
CLASSIFICATION OF WEEDS BASED ON LIFE CYCLE
Weeds are grouped in three classes. These include
(i) Annual weed (ii) Biennial weed (iii) Perennial Weed
These are weeds which complete their life cycle in one year. They grow, reach maturity and die within a year. Annual weeds include fridax plant, goat weed, spigelia and so on.
These are weeds that complete their life cycle in two years. The first year is used by the crops to grow and store food. Reproduction and maturity take place in the second year. Example of biennial weeds are wild carrot, yellow rocket.
These are weeds that take more than two years to complete their lifecycle or ripe for harvesting perennial weeds include giant star grass, guinea grass, carpet grass, centxo and tropical kudzu.
COMMON NAME BOTANICAL NAME
- Spear grass Imperata Cylindrica
- Guinea grass Panicum maximum
- Elephant grass Pennisetum prupuren
- Wild hemp sida spp
- Water leaf Talinum triangulare
- Goat weed Ageratum consoles
- Stubborn grass Elaisina indica
- W. D. Weed Tridax
- Pig weed Boerhavia
- Carpet grass Axonopus compressus
- Pigeon pea Cajanus caja
- Sensitive plant Mimosu pudica
- Witch weed Striga senegalenis