That crabapple tree hanging over the sidewalk sure looks great in bloom but the fruit makes a real mess when they drop to the cement and rot. This is a classic example of the wrong plant in the wrong place.

As always, there are several options to consider:

  1. Replace the Tree - This is a drastic step and should only be considered as a last resort. However, if the fruit is continually brought onto your nice white carpeting by everyone who visits...well.
     

  2. Hand Thinning - This would be tedious but may be an option if you have just one small tree in the wrong place. Enjoy the blooms but as soon as the petals drop off, either hand pick or cut off the small, developing fruit.
     

  3. Chemical Thinning - Certain plant hormones will cause fruit to drop off or not set in the first place. This is commonly done in commercial orchards to prevent a process called alternate bearing where a tree bears a heavy crop one year and a light one the following year. By thinning part of the crop each year, they get a nice crop each season.

    Several chemicals are used for this purpose including Naphthaleneacetic acid (NAA), Naphthaleneacetamide (NAD), maleic hydrazide (MH-30), chiorophenoxy propionic (3-CP) and dinitro-ortho-cresol (dinitro). Be aware that these products are not often available in the small amounts that the homeowner would need for one or two crabapple trees. They are usually sold in large volumes for commercial orchardists.

    The insecticide carbaryl (Sevin) also causes abortion of newly developing fruit. However, it would have to be sprayed during the late phases of bloom and this is when honeybees are still working the flowers. Bees are very, very sensitive to carbaryl so this is not a recommended procedure. We need all the honeybees we can get!

    With any of the chemical treatments, timing and the concentration of the spray mixture are keys. Follow the instructions on the product to the letter to have any success. Even in the best of times, you probably will not get 100% reduction of fruiting. It just doesn't work that completely or that reliably. Weather is also a factor that can cause a variation in success.
     

  4. Prevention - If you don't already have the tree in the landscape, avoiding the problem is still an option. Female Ginkgo trees produce a fruit that becomes very smelly when it drops to the ground. For this reason, reputable nurseries will only sell male plants. Some tree cultivars are seedless. There are literally hundreds of cultivars of crabapples in the market. Some are heavy fruiting varieties while others set small amounts of fruit. Choose the cultivar that fits your site needs.

The over production of fruit may be a problem but failure to bloom is also a concern.

Common chemicals used to limit the amount of fruit produced on landscape trees:
Species Chemical Time to Spray
Crabapples NAA petal fall
  NAD petal fall
Catalpa NAA full bloom
Ginkgo* MH-30 10 days after full bloom
Mulberry NAA full bloom
*only if you have female trees    
Note: Always follow the instructions on the product label to determine the appropriate concentration of the spray mixture.

Note: We have provided some general information and observations on this topic aimed at the home gardener. Before you take any serious action in your landscape, check with your state's land grant university's Cooperative Extension Service for the most current, appropriate, localized recommendations.

 

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