Fire and the Prairie - Burn Frequency and Time of Year

Fire and the Prairie

Burn Frequency and Time of Year

Although there are no hard and fast rules about how often to burn, there are a few generally accepted practices. Newly created prairies can be burned every year initially, then every two to three years after the vegetation is well established. Healthy remnant or intact prairies will benefit from burns every three to five years. Savannas need to be burned less frequently, every 10-15 years. The encroachment of woody or non-prairie vegetation is the determining factor.

For practical and ecological reasons, most prescribed burns are carried out in early spring. In southwestern Ontario, that is mid-March to late April and in more northerly areas, late April to mid-May. Since most prairie plants are warm-season perennials, they remain dormant at this time while the cool-season competing weeds are far enough advanced to get hit hard by the fire.

Some tallgrass managers vary the timing of the burn to benefit specific species. For example, summer burns decrease prairie grasses and shrub invasion and favour wildflowers. Consult an expert if you would like help fine-tuning the timing of the burn to manage certain plants.

How much to burn ?

Because of the subtle patchiness of the prairie landscape, fires do not burn evenly or completely. This is a good thing as unburned areas become refuges for species which, in turn, help re-populate the burnt areas. This is especially important for insects. For this reason, some managers burn only half of the site each time on a rotating basis.

Alternatives to burning

Where burning is not an option, mowing can be a partial substitute for fire. Mowing should take place late in the fall after the prairie plants have set seed and the birds have finished nesting. This can be done with the same frequency as burning. It is best to mow only half the site on a rotating basis to leave winter cover for wildlife. The clippings (thatch) should be removed so they don't blanket the ground and prevent sunlight from penetrating. As well, the clippings can be burned in a container and the ash returned to the prairie.

	Fire and the Prairie
	The Source of Fire
	The Impacts of Land Clearing
	FAQ's
	Prescribed Burns
»	Burn Frequency and Time of Year
	Prescribed Fire Decision Support System
	Recommended Reading