Gardening & Living in Grand Style
Leafcutter bees and microclimates...
by Michael Johnson
Utah State University Extension Agent, Grand County
Jun 29, 2017 | 1556 views | 0 0 comments | 321 321 recommendations | email to a friend | print
Leafcutter bees make holes in the leaves of plants, but the bees are beneficial pollinating insects and the damage will not do long-term harm. 
																		 Photo by Mike Johnson
Leafcutter bees make holes in the leaves of plants, but the bees are beneficial pollinating insects and the damage will not do long-term harm. Photo by Mike Johnson
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Summer has well and truly arrived with 100 degree-plus temperatures, which makes me so happy to find shade. These hotter days, along with the lack of rainfall and periodic winds, have also really raised some dust clouds the last few weeks. Through it all I am sure we still find considerable enjoyment in the many ways plants and insects do their thing.

Recently, I saw evidence of the leafcutter bee, which is in the Megachilidae family. Bees in this family are some of the most efficient pollinators, but due to their carrying pollen on the ventral surface of their abdomens, some might say their bellies, they aren’t that efficient at foraging because they have to make more trips than bees that carry pollen on their hind legs. What is neat about these bees is how they cut almost circular sections out of leaves to use to build their nests. They are solitary bees, but relatively gentle compared to honey bees. Being solitary doesn’t mean there won’t be other leafcutter bees in the same area building nests, just that each nest is only built by one bee, not as a group.

The reason I bring this up, besides the cool factor, is that many people are disturbed when they see their plants damaged. In my last column there was mention of adult root weevils making notches in leaves of plants and the larvae feeding on plant roots. That insect is not providing benefit and control is warranted. The leafcutter bee, though, is a great insect, being an extremely beneficial pollinator. So if you see some almost circular sections cut out of the edges of leaves just know you have a very beneficial neighbor helping to pollinate your plants, and only asking for some plant material, which won’t harm your plants, to make the next generation of helpers.

Over the last few years I have been watching the growth of some Vitex agnus-castus, or chaste trees, and crape myrtles growing along 100 south. The chaste tree is one of those plants that, depending on how you prune it, can look more like a large shrub or a tree. A native of the Mediterranean region, it’s suggested that the tree’s coldest USDA Zone is 6, but I have found it to be a plant that can be killed back to the ground regularly in Zone 6 and even sometimes in a zone 7. It has its own cool factor due to usually being filled with hundreds of spikes of lavender flowers in the summer. Bees and butterflies love it. In that same area are some crape myrtles that produce an abundance of flowers in very bright colors. Crape myrtles can also be killed back to the ground in a cold winter.

So besides the often awesome flowers of these plants, what’s the deal? These plants in particular have interested me due to my feeling that they are benefiting from a microclimate. Microclimates, as relates to plants, are places where the growing conditions differ from the surrounding area. This means areas where the sunlight, moisture, humidity, wind and/or temperature are more conducive to plants that might be considered on the fringe climate-wise. Plants in microclimates are helped due to their location, which is often protected by natural features, buildings or other plants. Since I have seen both of these plants fail to survive in other locations in Grand County, I wondered how well these would do when I first saw them planted. It’s obvious now that this location — which has a high block wall, concrete sidewalk, and asphalt street, all in close proximity — helps to keep the temperature more moderate during the winter, even though snow can last there for quite a while due to winter shade. The likely overall warmer temperatures in the winter, along with blockage of wind, I believe, have allowed the chaste trees in particular to grow into some of the bigger specimens I have seen in town.

This is just one instance, but we see other microclimates, particularly with fruit trees, where the fruit on trees in one location may be completely wiped out, but others in protected areas do fine. This is just another interesting topic in the world of gardening.

Thought for the day: “Yesterday I did nothing and today I’m finishing what I did yesterday.” —Anonymous

Previous articles are available at The Times-Independent website, www.moabtimes.com. Have an idea you’d like Mike to consider writing about? Want more information about these topics? Call the Utah State University Extension Grand County office at 435-259-7558 or email Mike Johnson at mike.johnson@usu.edu.


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