Honey bee forage: black locust
The black locust tree, Robinia pseudoacacia, is famous for producing a fruity and fragrant honey that ranges from water white to lemon yellow to yellowish green. A batch of monofloral black locust honey with little cross-contamination from other flowers can be as clear as a glass jar. The honey is high in fructose so it can be stored for long periods without crystallizing.
The black locust tree is native to eastern and southeastern North America, but has spread throughout the United States and much of Canada. A member of the Fabaceae (pea family), the tree has nodules of nitrogen-fixing bacteria on its roots which make it an excellent species for re-vegetating poor or damaged soils. In addition, its tolerance for low pH has made the tree useful for strip-mine reclamation sites.
Black locust grows quickly and averages 40-70 feet tall at maturity. It is often planted as a source of firewood, not only because of its fast growth but because the wood burns very hot. Although the tree does not tolerate shade or extreme cold, it grows well in a variety of moisture, fertility, and slope conditions.
Nectar flows vary from year to year
Although it is considered a major honey plant in the eastern U.S., the black locust does not always produce a crop of honey. Nectar flow is very dependent on local weather conditions and some years the flowers yield little or no nectar at all. Some areas of the country report good crops once in every five years, but the frequency varies with the location.
Even when the flow is good, the flowering period is short. The flowers, which bloom in long, white racemes, open sometime between April and June for about ten days. During the rest of the year the trees are excellent habitat for invertebrates, birds, bats and other small mammals.
Nancy, a reader from Shady Grove Farm in Kentucky, has been enticing me with delectable descriptions of her current black locust flow. Below is a photo she sent of a tree in full bloom.
A final note: The black locust should not be confused with the honey locust, Gleditsia triacanthos. Ironically, the honey locust produces very little—if any—honey. The tree was nicknamed “honey locust” because of the sweet pulp which was used for food by some of the North American tribes.