Controlled burns play a crucial role in maintaining healthy prairie ecosystems. The timing of these burns depends on various factors, including the type of prairie and the specific goals of the management. Here are some guidelines for conducting controlled burns on prairie grasslands:

1. Frequency and Timing:

   • Newly created prairies: These can be burned annually initially, and then every two to three years once the vegetation is well established.
   • Healthy remnant or intact prairies: Benefit from burns every three to five years.
   • Savannas: Need less frequent burns, typically every 10-15 years.
   • Timing: Most prescribed burns are carried out in early spring:
     • In southwestern Ontario, that’s mid-March to late April.
     • In more northerly areas, it’s late April to mid-May.
     • During this time, prairie plants remain dormant, while competing cool-season weeds are advanced enough to be affected by the fire.
     • Some managers may vary the timing to benefit specific species¹².

2. Amount to Burn:

   • Prairie fires don’t burn evenly or completely, which is beneficial.
   • Unburned areas serve as refuges for species, especially insects.
   • Some managers opt to burn only half of the site each time on a rotating basis¹.

3. Alternatives to Burning:

   • When burning isn’t feasible, mowing can be a partial substitute.
   • Mow late in the fall after prairie plants have set seed and birds have finished nesting.
   • Mow only half the site on a rotating basis to leave winter cover for wildlife.
   • Remove clippings (thatch) to prevent them from blocking sunlight.
   • Burn the clippings and return the ash to the prairie¹.

4. How Grassland Plants Survive Fire:

   • Growing points (meristems) of many prairie grasses and flowers are below ground, protecting them from fire.
   • Previous year’s stems and leaves provide fuel, while the growing point remains cool underground.
   • Meadows are not fire-dependent and do not benefit from burns; they grow where soil has been recently disturbed or tilled¹.

In summary, early spring is the best time for controlled burns on prairie grasslands, but specific timing may vary based on local conditions and management goals.