What is a Weed?

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What is a Weed?

Weed Management in the Home Garden

The simple definition of a weed is:

A plant that is growing in an area where it is not wanted.


The complicated definition is:

Weeds are plants which are undesirable, persistent, damaging and interfere with growth of other crop plants thus affecting human activities, agriculture, natural processes and economy of the country.

Weeds can impede the proper development of a crop as they:

  1. Compete for light, moisture and nutrients affecting quality and quantity of produce
  2. Interfere with and damage harvesting equipment
  3. Harbor pests and diseases


In addition to adversely affecting the Crop they also:

  1. Have toxic properties that can cause health problems to humans and animals
  2. Contaminate aquatic resources
  3. Interferes and adversely affects natural ecosystem.

Methods of Weed Control

  1. Manual Weed Management
  • Via hoeing or hand weeding
  • Vegetables that are delicate as seedlings
  • Done when weeds are young
  • Before roots are intertwined and
  • Before seeding
  1. Mulching
  • During dry season
  • Smothers weeds


  1. Drip Irrigation
  • Distributing appropriate amounts of water to root system
  • Reducing water loss
  • Allowing surface of soil to dry and thereby offering less water for weeds


  1. Cultural control methods
  • Controlled spacing
  • Good crop canopy
  • Optimum growing environment for plant
  • Crop rotation


  1. Chemical Control


  1. Integrated Weed Management


Chemical control of weeds is not encouraged in the home garden as the space may be small, so leaching and cross contamination can easily occur. This can cause damage to crops, seedlings and even you!

Chemical Herbicides also commonly known as Weedicides can be classified based on several attributes.

  1. Classification Based on Translocation
  • Systemic/Translocated – passes all through plant and kills it
  • Non-systemic/Contact- kills where it comes in contact with


  1. Classification Based on Time of Application
  • Pre-emergent – kill weeds before emergence from soil i.e. seeds
  • Post-emergent- eradicate weeds that have already emerged from soil


  1. Classification -Method of Application
  • Soil Applied – to soil
  • Foliar Applied – to plant


  1. Classification Based on Specificity
  • Selective Herbicides- kills certain plants
  • Non-selective Herbicides- kills all plants present


  1. Classification Based on Site of Action
  • Herbicides generally target essential metabolic processes in plants e.g. photosynthesis, mitosis or amino acid biosynthesis. These processes are common in both crops and weeds. Herbicides can stop these essential process thereby killing the plant.

So remember to choose your method of weed control properly so your crop does not suffer and you do not have a loss of production.


Video –Weed Control



Information courtesy the Extension Training and Information Services (ETIS) Division

Ministry of Agriculture, Land and Fisheries


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