April 11, 2015

1 - Old tree stumps can be composted in the middle of a compost pile instead of grinding or digging them out.

Yard and Garden April 11, 2015

Q.

I have an old tree stump in the place I was thinking of putting a compost bin. Will it hurt to just build compost over the stump and hope it rots or should I dig the stump out?

A.

The stump may cause some problems as you try to turn the compost, or it may form a back-stop to help you turn the compost. The pile of decomposing material, properly moistened around the stump should speed the decomposition of the stump. Another option is to cut the stump as close to the ground as possible so that it is less a hindrance as you turn the compost. To speed the decomposition of the stump you can drill holes in the stump to allow even more contact with the decomposing materials of the compost and the microorganisms that will cause the decomposition of the stump. Use one-half in to one inch spade bits on a drill to make the holes.

However, since you said "old" stump I wonder what kind of tree produced the stump. If the tree was a juniper or Arizona cypress tree the wood is very resistant to decomposition and may take longer to decompose than most other tree stumps. In that case cutting it out of the way and drilling the holes may make even more sense. If the tree was a cottonwood or willow, the wood will decompose quite rapidly once the composting environment develops. Frequent additions of high nitrogen materials such as manure or kitchen scraps and water will help any stump decompose. The end product of the decomposition of the stump will be good compost along with the compost formed from other materials.

If it is important to get rid of the stump quickly, you can dig it out, cutting the roots and then pulling with a vehicle or with a pulley system. Most trees do not have deep root systems that will make removal difficult. I have heard of people burning the stumps as well. If the stump is in a location where burning is not hazardous to structures and surrounding vegetation that is an option, but be very careful. To make the burning more complete you can drill the holes described above and fill the holes with kerosene or diesel fuel. Do no use gasoline or lighter fuels. Allow the fuel to soak into the wood, perhaps refilling the holes several times over several weeks. Once the wood has absorbed the fuel ignite the stump. Be sure the area around the old stump for a considerable distance is free of combustible materials and watch over it carefully. Do this when there is no wind forecast for several days. It may take quite a while for the stump to completely burn and wind could carry embers to areas where the fire is not wanted. Personally I prefer the idea of turning the old stump into compost. It is safer and the end product is more useful, but composting will take longer.

Marisa Y. Thompson, PhD, is the Extension Horticulture Specialist, in the Department of Extension Plant Sciences at the New Mexico State University Los Lunas Agricultural Science Center, email: desertblooms@nmsu.edu, office: 505-865-7340, ext. 113.

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