Issue: June 2, 2007

Tree stumps

Question:

At a conference two years ago we discussed a compound that will cause stumps to decay. I have forgotten if it was ammonia sulfate or ammonia nitrate. I should have written it down. I would appreciate elucidation.

Joe S.
Northern NM

Answer:

There are a lot of things recommended to apply to stumps. However, the best product to speed the decay of a dead or freshly cut stump is any high nitrogen fertilizer. The nitrogen feeds the fungi and bacteria that decompose (compost) the stump. Both ammonium sulfate and ammonium nitrate are nitrogen fertilizers and contain no phosphate or potassium. To decompose the stump, only nitrogen needs to be added. The ammonium nitrate has higher nitrogen content, but may not be as readily available. The ammonium sulfate is lower in nitrogen analysis, but it will work well. Manure is even lower in nitrogen, but it can also be used to speed the stump's decay.

With either product the best way to treat the stump is to drill holes into the stump across the whole cut surface. Fill these holes with the nitrogen. As the nitrogen fertilizer dissolves, you can add more if you wish. After applying the nitrogen fertilizer, the stump must be kept moist for the fungi and bacteria to work effectively. One way to keep it moist is to keep it covered. Don't try keeping it moist by wetting it with a hose because this may dissolve the fertilizer and wash it away from the stump. A simple way to keep it moist is to mist or spray it carefully and then cover the stump. The covering may be plastic or a compost pile. The compost pile concept helps create an environment of high microbial activity around the stump.

Another idea that some people like is to put a raised flower bed or a large flower pot with no bottom around the tree stump. This raised bed or pot is then filled with good planting soil and flowers or vegetables planted in them. As you water and fertilize to keep the flowers and vegetables growing, you will encourage the rapid decomposition of the stump. This may take several years, but the stump has been concealed by an attractive landscape element.

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.

For more gardening information, visit the NMSU Extension Horticulture page at Desert Blooms and the NMSU Horticulture Publications page.

Send gardening questions to Southwest Yard and Garden - Attn: Dr. Marisa Thompson at desertblooms@nmsu.edu, or at the Desert Blooms Facebook.

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