Weed Management

Weed Management Practices

Weeds in a pasture can be a serious concern and should be dealt with as soon as possible! Below are a few of the main weed species found in the lower mainland that have serious health hazards for your livestock associated with them. For any additional information visit the resources page or take a look at the Land Management Guide.

Weed species common to lower mainland Pasture conditions that encourage growth Detrimental health effects
Creeping buttercup (Ranunculus repens)

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Acidic and wet (boggy) conditions
  • Contains toxins that cause serious inflammation  in the digestive tract
  • Sap from stems can cause blistering on the skin or mucous membranes and even around the hooves of horses
  • Mouth blisters, colic, bloody urine or diarrhea, twitching of the eyelids, loud breathing and a weak pulse
Field horsetail (Equisetum arvense)

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Poorly drained and acidic soils
  • Especially poisonous for young horses
  • Jaundice, loss of appetite, weakness, staggering gait, excitability and paralysis
Tansy ragwort (Senecio jacobaea)

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© Copyright Nick Smith and licensed for reuse under this Creative Commons Licence.

Damp and acidic conditions with sparse pasture grass
  • Contains liver-damaging alkaloids
  • Weakness, liver failure, high temperature, incoordination and yellow mucous membranes


Practical Weed Management Strategies

Since there are no effective treatments for any of these plant poisonings the best mode of defense is preventative pasture management. If the pasture happens to be quite acidic (which you can determine through a simple soil test) then you should lime your fields to make them more alkaline. Dolomite lime is the most effective form for pastures and can be easily obtained at local garden centres. Do not use slow release lime as this can cause potential health problems for your horses. Also, let the pasture rest for one to two weeks after liming before turning your horses out.

Additionally, spreading finished horse manure compost and over-seeding with a good grass mixture tailored to your region will go a long way to out-competing these nasty weeds. The more dense the grass, the less dense the weeds will be. Horses only graze weeds when there is not enough grass available in the field for them. Therefore, we need to ensure that the fields are not overgrazed and are left to rest when necessary.

A full weed management plan could include the following:

  • Liming once in the spring and possibly again in the fall depending on the results of a pH test on your soil (pH should be no lower than 6.5)
  • Aerating in the spring and again in the fall
  • Thinly spreading a layer of horse manure compost each spring and fall (ensure that there is enough nitrogen in the compost). If your grass is longer than 2 inches you will need to mow it prior to spreading.
  • Chain harrow the compost into the soil to break up any clumps left in the field
  • Do a light broadcast over-seeding of the pasture with your pasture mix to ensure that grass density is maintained to discourage the presence of weeds.
  • Hand pull or spot torch any weeds in the pasture prior to them going to seed.

For more information on weed management here is a BC Field Guide to Noxious weeds and Invasive Plants, you can visit the Ontario Ministry of Agriculture, Food and Rural Affairs website, or take a look at the Land Management Guide.