The menace of black locust!

Black locust (Robinia pseudoacacia) is one of those trees you can love to hate, although because it forms heaps of pretty flowers and a nice perfume, many people love it. It is fiercely invasive and should never be allowed anywhere near a natural area.

In our area it usually flowers in late May and the leaves appear soon after.

It is a member of the bean family, and really large specimens are often present. One of its worst characteristics is its clonal growth, similar to aspen.

It is an easy tree to spot when it is in flower (see the photo above), but once it is finished flowering it simply blends into the woods.

According to the Wisconsin DNR web site, black locust is native to the southern Appalachians and Ozarks but was introduced throughout Wisconsin in the early 1900's because its aggressive growth pattern and extensive root system discourage soil erosion. Black locust wood is also valued for its durability and high fuel value, and provides good forage for bees. However, it forms very dense stands and is capable of completely shading out all native vegetation. It should definitely not be planted in natural areas.

The Prairie Enthusiasts has been battling black locust at Walking Iron County Park for at least ten years. The photo above shows the extensive growth at the entrance to the Park, and there are large stands off Park lands as well. In certain parts of the Park one can find dozens of six foot high specimens. Control can be done by cutting and treating the cut stems with herbicide (triclopyr or chlorpyralid), but because of the large number of stems this is a major job. Kay Bongers has been the lead worker at Walking Iron, and usually has one or two work parties during the winter. If enough people show up, it is possible to eradicate it from one of the areas where it is particularly bad.

Fortunately, we don't have any black locust at Pleasant Valley Conservancy. The nearest trees are about 2 miles away, but I have been watching it move from one woodlot to the next over the past couple of decades.

Here is what the Plant Conservation Alliance has to say about it: "Black locust poses a serious threat to native vegetation in dry and sand prairies, oak savannas and upland forest edges, outside of its historic North American range....Once introduced to an area, black locust expands readily into areas where their shade reduces competition from other (sun-loving) plants. Dense clones of locust create shaded islands with little ground vegetation. Lack of ground fuel limits the use of fire in natural disturbance regimes."

Keep an eye out for it. Don't let it get started in your area!