This week the air in my neighborhood smells so sweet. The black locust trees are in bloom.
Black locusts (Robinia pseudoacacia) are common in Pittsburgh because they’re one of the first trees to grow in poor, disturbed soil. Our area has a lot of habitat for them, generated by people and nature — bulldozers and landslides.
Black locusts are ugly in winter with gnarly bark and twisted branches but they are sweet in May. The trees are in the pea family and it is evident in their flowers. Here’s what they look like in bloom.
The flowers are attractive to bees and birds. I’ve seen rose-breasted grosbeaks use their large beaks to grab the base of the flowers, then twirl to make the petals fall off. They swallow the nectar end.
Black locusts usually reach their peak on May 12 but they’re late this year. Look for these beautifully scented trees before the flowers fade in about 10 days.
Enjoy the sweet smell of trees.
(photos by Kate St. John)
Like many legumes, black locust engages in a mutualism with bacteria in genus Rhizobium. The bacterial cells live in the trees’ root nodules and get nutrition from the host. In turn, the bacteria fix atmospheric nitrogen in a form (usually NH3) that the host can use. This explains in part why black locust can colonize sites of poor soil quality.
Even better than the fragrance (which I love) is the fact that the blossoms are edible! Learned that from Charles Bier – you can put them in pancakes/fritters!
While very pretty they send my allergies into overdrive.