Weed Control

Course CodeBHT209
Fee CodeS2
Duration (approx)100 hours
QualificationStatement of Attainment

Controlling Weeds

  • Learn to identify and manage weed problems
  • Study lots of different techniques for controlling weeds
  • 100 hour, self  paced course -expert tutors provide personalised feedback throughout

Weeds are a major threat for many reasons. They compete with garden plants, crops and invade natural environments, often replacing nativenative  plants. Weeds make your preferred plants weaker and they can bring unnecessary allergens or toxins into the environment, and overtake large areas.

Young weeds are far easier to control than older and more established weeds. There are many different ways of controlling weed growth, and the effectiveness of each technique is related to the varieties of weeds being controlled. Some chemicals, for instance will effectively kill certain weeds when they are in the early stages of growth, but will not control other types of weeds. You may need to be able to distinguish between types of weeds to determine whether the chemical will or will not work.

Understanding weeds is the key to controlling them, whether in a garden, farm or elsewhere and controlling weeds can save you a great deal of time, money and environmental damage.

This course shows you what weeds are, how to identify weeds, and how to control weeds.

Lesson Structure

There are 8 lessons in this course:

  1. Weed Identification
    • review of the system of plant identification
    • general characteristics of the weeds
    • further information
    • contacts, etc.
  2. Weed Control Methods
    • practical research on management of weeds
    • understanding terminology
    • use of mulches
  3. Chemical Weed Control
    • review of commercial and domestic herbicides
    • determining what differentiates them
    • their availability and use.
  4. Weed Control In Specific Situations
    • understanding weed control strategies for particular situations
    • accessing first hand information about weed control from industry leaders and determining a weed control program for five different sites.
  5. Safe Chemical Application
    • reviewing what types of chemicals and application methods are used in the industry and the required safety procedures for the handling and administrating chemical herbicides.
  6. Non-Chemical Weed Control
    • determining any detrimental effects chemical herbicides have on the environment
    • reviewing non-chemical applications
    • their effectiveness.
  7. Dealing With Specific Weed Control Problems
    • current industry practices for weed control
    • effects on the environment in relation to specific weed control problems.
  8. Developing A Major Weed Control Program
    • a practical lesson where the student can fully demonstrate their understanding of weed control by devising a weed management plan for a designated area.

Each lesson culminates in an assignment which is submitted to the school, marked by the school's tutors and returned to you with any relevant suggestions, comments, and if necessary, extra reading.


  • Distinguish between different types of weeds, and identify common weed species, growing in your locality.
  • Explain characteristics of different weed control methods.
  • Explain the use of chemical herbicides to control weeds.
  • Specify appropriate weed control methods, for different types of situations.
  • Determine appropriate techniques for the safe application of chemical herbicide in a specific situation.
  • Explain different non-chemical weed control methods.
  • Devise appropriate methods for control of weeds, for specific problems, in both the horticultural and agricultural industries
  • Determine a detailed weed control program for a significant weed problem.

What You Will Do

  • Observe and consider over 100 different varieties of weeds and prepare plant review sheets for different weed plants.
  • Make up a list of information resources.
  • Plant, grow and observe different varieties of weeds.
  • Make drawings of young seedlings of at least fifteen different weeds.
  • Speak/interview people who have to deal with weed control in their daily life.
  • Visit a nursery, garden shop or hardware store that sells herbicides to the public.
  • Visit at least one supplier of herbicides for industrial and agricultural use.
  • Contact larger chemical companies for leaflets on different herbicides.
  • Investigate at least two workplaces where weed control programs are regularly carried out.
  • Visit and inspect different sites where weeds are a problem.
  • Photograph different places that have been treated with weedicides.
  • Contact your local Department of Agriculture or Lands Department for researching purposes.
  • Visit several farmers who raise different types of livestock.
  • Develop a 12 month guideline for an integrated weed control program for a particular site.

Suggested Reading

Have you read our ebook on Weeds?
written by John Mason, our principal, and staff from the school.


The generally accepted definition of a weed is any plant that, for some reason or other, is unwanted in a particular position. Any type of plant has the potential to be a weed. Common reasons why people do not weed species to grow include:

  • Competition - weeds can compete with your desired plants for space, light, nutrients and moisture.
  • Safety - some plants may be poisonous or cause allergies (e.g. St John's Wort, Bathurst Burr, Parthenium Weed). Others may have spines, spikes (e.g. Giant Devil's Fig, Currant Bush and Chinese Apple) or sharp grass seeds that can injure animals and humans (e.g. Spear Grass).
  • Harbouring or hosting pests and diseases - some plants may act as hosts or as attractants to pests or diseases. Others may provide a safe haven for pests such as rabbits and foxes.
  • Tainting - some weeds (e.g. Capeweed, Wild Garlic) can taint the taste of meat and milk from animals such as cattle, sheep, goats and pigs.
  • Contamination - plant parts, particularly seeds, can get caught up in clothing, or can contaminate produce, such as grains, or get entangled in animal fur or fleece, or fibre crops (e.g. cotton), or in hay.
  • Interfere with cultivation - some plants can become entangled in machinery making tasks, such as cultivation, mowing, or machine harvesting difficult, and possibly damaging machinery.
  • Soil erosion - some weeds are very competitive, and will easily shade out other more desirable plants. If the weed is only seasonal (eg. an annual, or dies back during winter), it may leave exposed soil that may be easily eroded.
  • Aesthetics - some plants may be weeds simply because they look bad, or they have offensive odours.
  • Environmental - these are plants that invade native vegetation, displacing the indigenous species. This can severely affect local flora and fauna populations (e.g. Lantana, Camphor Laurel, Singapore Daisy and Water Hyacinth).


Controlling Weeds

Once it is determined that a particular plant or group of plants is a weed, we need to select a suitable method to control it. Chemical methods are the mainstay of weed control on most farms. Weedicides certainly give a quick result, but also have the following problems:

  • They can be quite expensive.
  • There may be legal requirements with regard to their use and storage, and training of operators.
  • Chemicals can damage other plants, especially if they are applied in windy or hot conditions.
  • They can wash off in rain and either don't work, or they may run into other areas, causing damage to other plants.
  • If you get the concentration wrong, chemicals can actually promote rather than deter growth. Some blackberry killers, for example, used at low concentrations cause more rapid growth.
  • High concentrations can poison the ground and, in extreme cases, prevent further plant growth.
  • Chemicals can be harmful to animal life including humans, domestic pets, birds, fish, and soil life.
  • The manufacturing processes involved in making the weedicides can cause pollution problems.
  • Old weedicide containers pose a safety risk unless carefully disposed of.

Even in sustainable farming methods such as conservation tillage, chemical use is common. It would be extremely difficult for most farmers at present to completely stop using such chemicals; however there are some non-chemical control methods that can be readily applied and which can significantly reduce the farmer’s dependence on weedicides. You should first:

  • Know the weed or weeds you are dealing with.
  • Know how those varieties grow, and what conditions they do and don't tolerate.
  • Then create conditions which they don't like.

You need to consider whether you want to kill or just control the weeds. When you know these things you can consider which method is best for your situation.



  • Those working in garden maintenance, cropping, nurseries, farms
  • Weed control contractors
  • Horticulturists
  • Agriculturists




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