DEFINITION OF WEED
Weed is any plant which is not cultivated and is growing where it is not wanted. Such a plant istherefore a nuisance to the farmer. Examples; commelina, goat weed or the common water leaf(Talinum triangulare) growing in a cassava field.
Types of Weeds according to lifecycle
- Annual weed: They grow and complete their life cycle in one year
- Perennial Weeds: They grow for more than one year.
Types of weeds according to the shape of their leaves
- Broad-leaves Weeds: These are weed plants with broad leaves. They are dicotyledonous plants
- Grasses and sedges: These plants have long, thin leaves and are monocotyledonous plants.
Examples of weeds
Some common weeds found in Nigeria are:
Common name Botanical name
- Goat weed Argeratumconyzoides
- Guinea grass Panicummaximum
- Pig weed Amaranthusspinosus
- Bahama grass Cynodondactylon
- Elephant grass Pennisetumpurpureum
- Carpet grass Axonopuscompresus
- Tridax Tridaxprocumbens
- Spear grass Heteropogoncontortus
- Sida weed Sidaacuta
- Water leaf Talinumtriangulare
Characteristics of Weeds
- Weeds grow very fast and cover the land area very quickly.
- Many weeds produce fruits and seeds which are easily carried and spread all over the place by humans, animals, wind and water.
- Many weeds are persistent, which means that they remain in the ground throughout the year and continue to grow as long as the weather conditions in the area permit and especially when cultivated crops are grown on the land.
- They compete with crops for nutrient, space, water and sunlight.
- They are resistance to harsh climatic conditions.
- What are weeds?
- List five examples of weeds and their botanical names.
Advantages of weed
- They serve as source of food to man.
- They serve as source of feed to animals.
- They increase fertility of nutrient status of soil directly or indirectly.
- They help to control erosion.
- They serve as source of medicinal herbs for man.
Disadvantages of Weeds
- Weeds compete with cultivated crops for the nutrients in the soil.
- Weeds grow rapidly hence they crowd and cover cultivated plant thus prevent them from growing.
- They make land cultivation difficult
- Weeds which use crops as support can cause strangling to death of such crop. e.g Parasitic weeds.
- Transmission of insects, fungi and other organism harmful to crops.
- They results in the reduction in value and quality of farm produce.
- Wastage of money in control.
- They increase farmers cost of production.
- They lead to loss of livestock when they consume poisonous weeds.
GENERAL EVALUATION/REVISION QUESTIONS
- What is a weed?
- Name three examples of weeds and their botanical names.
- Mention three characteristics of weeds.
- State five negative effects of weeds on crops and the economy.
- _____ is an unwanted plant growing among cultivated crops. A. Weed B. Crops
- Plants D. Animals
- The following are characteristics of weed except _____ they grow very fast B. they produce many fruits C. they remain in the ground through the year D. they are mainly annual weeds.
- _____ are weeds which grow and complete their life cycle in one year
- Perennial crop B. Perennial weed C. Annual weeds D. Biennial weed.
- The following are effects of weed except a. They make land cultivation difficult, b. Weeds compete with cultivated crops for the nutrients in the soil c. Transmission of insects, fungi and other organism harmful to crops d. They results in the increase in value and quality of farm produce.
- The scientific name of goat weed is ____ A. Amaranthus spinosus Mimosa pudica
- Argeratum conyzoides D. Striga hermonthica.
- Define weed.
- Mention the common names and botanical names of four weed you know.
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