Master Gardener Q&A

by Dara Palmer
MSU Extension Master Gardener Coordinator

Q. We had a tree removed from our lawn last year and have noticed a round discoloration in the grass around the stump. What is happening? - Missoula County

A. It's very likely you have a fairy ring in your lawn. Fairy rings appear as circular rings of either darker green or brownish grass, sometimes with mushroom growth at the edges. This is caused by a fungus that feeds on the decaying organic material in the soil, like your tree stump for example. The damage is cosmetic and will likely disappear naturally on its own. If you want to act, there are a few things you can do to help manage the fairy rings. Consider removing the tree stump to reduce the amount of decaying material available. If that is not feasible, try core aeration to remove thatch that may harbor the fungus, practice proper watering and mowing methods to maintain a healthy lawn and establish a regular fertilization schedule.

Q. Why do the apples drop off my apple tree in late August or early September? - Powell County

A. Dropping of fruit can be due to a variety of issues such as drought, insects, and disease and these issues should be thoroughly investigated to determine the cause. Fruit trees naturally drop excess fruit as a self-regulated thinning process to prevent over-cropping. This natural fruit drop typically occurs in early June but can occur later in the growing season should the tree not be able to support all the fruit through to maturity. There are four diseases commonly seen on apple trees in Montana and they are: Fire Blight, Cedar-apple Rust, Powdery Mildew and Apple Scab. The Montguide Important Apple Diseases in Montana and Recommended Varieties for Resistance provides detailed information on these diseases and can be accessed via the Internet at

Q. Do I need to fertilize my lawn? If so, how often and when? - Pondera County

A. Fertilizer may be needed to keep your lawn grass looking green and healthy. General recommendations call for fertilizer to be added three times during the year at Memorial Day, Labor Day and Columbus Day. Standard fertilizer rates are often found on fertilizer bags. If you are using standard rates and your lawn is not thriving, or if you wish to reduce the risk of, or diagnose, a potential nutrient deficiency or toxicity, soil testing will help you determine if your lawn has abnormal levels of nutrients. For more information, visit When fertilizing, also be sure to water sufficiently.

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