Tom's Blog

Thursday, December 8, 2016

Now is the Best Time for Burning Brush Piles

I’ve posted on this before but it doesn’t hurt to repeat it.

Restoration work, especially of oak savannas, results in lots of downed timber. Although good logs can be turned into lumber, and less good logs into fire wood, there is always lots more woody biomass that ends up on piles.

Some of these piles might be saved as critter habitat, but because they complicate controlled burns, most of them have to be eliminated by burning.

In the early days of our restoration work at Pleasant Valley Conservancy, we had large numbers of brush piles. On the South Slope alone, in the years 1999-2000, we had 230 large piles, all of which we burned that winter. (See photo below)

Kathie and Pat Schrader lighting brush piles on the South Slope of Pleasant Valley Conservancy; Jan 2000
In April 2000 Dane County did high resolution air photography of the whole county, and on the photo of our property every one of those burned spots can be seen and counted.

There is a skill in building a good burn pile. The secret is to make the pile compact, which means cutting many of the smaller branches so that the wood can lie flat. The more compact the pile, the better it burns. A chain saw or lopper is essential when building a burn pile.

Piles should only be burned when there is snow on the ground. This ensures that the fire stays put and the pile can be burned safely. (In our area, we need a DNR permit for any burning we do after January 1, but we don’t need a permit if there is snow on the ground.)

The best fuel to get a brush pile started is drip torch fuel (2 or 3 parts diesel to 1 part gasoline.

The photo here shows a well-made brush pile at the early stages of the burn.

If there is a lot of snow on top of the pile, it will probably burn better if the snow is blown away with a leaf blower.

The best routine is to burn a lot of brush piles the same day. Get started early, as it will take all day to finish the job on each pile. Start all the piles in sequence and make sure the fire is going well at each pile before moving on to the next. Return to those lighted earliest after about an hour, and check on the fire. After lunch, return again, starting again at the pile lighted first.

The watchword for the afternoon is “consolidate”. A good garden rake or shovel is best, and heavy leather gloves. There will be lots of unburned wood at the edge of each pile. Use the tool to lift them and throw them into the center of the burning pile. For smaller pieces, pick them up by hand and toss them into the center of the pile.

Go around the whole periphery of the pile, and get everything back on to the pile.

Continue around the circuit of piles, consolidating each one before moving to the next.

At the end of the day the goal should be that all the wood is burned up, with only ashes left.

I’m often asked if burn piles don’t sterilize the soil underneath. The answer is yes, although soil is a poor conductor of heat, so it should only be a top thin layer that is sterilized. But the bare area should be planted with a good seed mix similar to that of the surrounding habitat. Blow away all the ashes with a leaf blower, leaving only bare soil. The planting can be done any time, although best in the winter so that the seeds have a chance to get stratified.

Our experience is that even the end of the first growing season, you will hardly know where the burn pile was, and by the following year everything will be back to normal.

Be sure to wear a fire-proof jacket, because a burning pile creates lots of sparks. You don’t need Nomex, but any old cloth jacket that won’t burn.


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