Tom's Blog

Friday, February 24, 2012

Dealing with brush piles

Lots of cut brush is created from savanna (and to a lesser extent prairie) restoration. Depending on the situation, brush is either burned as it is cut, or it is piled for later burning. We have dealt with hundreds of brush piles at Pleasant Valley Conservancy, and our technique has improved through the years. (In the winter of 2000 we burned 235 brush piles on the south-facing slope!) Mostly, we have learned the brush-pile "art" from Paul Michler, one of our contractors. He introduced the use of drip torch fuel (2-3 parts diesel to 1 part gasoline) to start the fire.

Every year we build a brush pile at the edge of Pleasant Valley Road, and use it for the odd brush that we need to get rid of. We can pull up the truck and toss brush on the pile. Also, bags of sweet clover, hedge parsley, or other invasive weeds are tossed on this pile. By the end of the season we usually have a fairly substantial pile. This year it was larger than normal, so we ended up with two separate burns.

The secret of burning a brush pile is to start with really dry wood. In December 2011, when we did the first burn on this pile, some of the wood had not "cured" long enough, and only part of the pile burned well. So we reconsolidated the rest into a second pile and let it cure for another two months. As the photo shows, this pile burned very well. After getting it started, we started working on willows in the wetland.

Within an hour this pile was mostly burned up, at which time we returned and consolidated the partially burned wood. Consolidation is the main work on a burn pile, although I find it enjoyable. You need a pair of sturdy (but old) leather gloves. A long-handled pitchfork is also essential, although a garden rake or shovel will also serve. The key is to build a small, hot fire with smoldering logs in the center of the former burn pile and carefully place all the other partially burned logs on top. Keep the burning pile as compact as possible. It may take an hour to consolidate a pile properly, but you'll be happy you did so. Done right, you should be able to return the next day and find only ashes.

Since the fire sterilizes the soil, it is important to plant the area with a good seed mix. First, the ashes have to be removed, either with a leaf blower (if it hasn't rained or snowed) or a garden rake. Then hand sew. Done right, in a year or two the site of the burn pile will be no longer visible.

As the photo shows, the flame height can be high so it is essential that a burn pile be built out in the open, away from any trees. When clearing a heavily forested area, it may be difficult to find suitable sites for piles. If so, then it is important that the piles not be built too large. Since you are going to burn the woods, you don't have to burn the piles separately, as they will quickly burn up when the woods is burned.

Farmers in the hill country of southwestern Wisconsin always burned their hill pastures in the early spring in order to encourage green-up. I was interested in how they started their burns and was fortunate to have a neighbor (now deceased) who had lived on his farm all his life. He told me that their pasture burns usually started as "escapes" from burning brush piles. Once the fire started, they just let it burn. The farmers around here still cut lots of brush, mainly along the edges of their planted fields, but these days rarely do they burn the piles. They just let them sit, where they become great wildlife habitat.


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