Saturday, February 23, 2008

How to Identify a Black Locust Tree in Winter

I spent the day getting signed up with the Budburst Project. I'm going to be reporting on nine plants that grow on my block. My instructions are to report the following markers: budburst (also known as first leaf, when at least three leaf buds have unfolded), full leaf (95% of leaf buds are unfolded), first flower (when you can see the stamens of the flower), full flower (when at least 50% of the flowers are open), end flower (when at least 95% of the flowers have dried up) and seed or fruit dispersal (when seeds or fruits start dropping naturally).

I chose the following plants from a long of possibilities.
American linden, common dandelion, common yarrow, forsythia, lilac, California poppy, purple passion flower, field mustard and white clover.
All can be found on my block except for the linden which is kitty corner from the northwest corner of my block.

I wanted to add a black locust tree to my list, since black locusts have always been magical trees for me. My mascot tree on the UW campus, the one I always hug (furtively) before and after my classes, is a black locust. But I wasn't sure if the locust tree on my block was a honey locust or a black locust.

Luckily I have Jacobson's Trees of Seattle, a wonderful reference guide which not only describes each tree but also provides addresses and directions so one can find specimens of each tree in residential neighborhoods and parks. (If your town doesn't have such a reference guide, you should create one. It's marvelous.)

Jacobson gives a nice breakdown of the differences between the two trees. Black locusts are likely to be older, grow wild and have extensive root suckers, while honey locusts have usually been planted, are younger and don't put forth suckers. You can see in this photograph of mine, how prolifically black locusts put forth suckers. This was was one of two trees in my neighborhood that were cut down to put up some condominiums. The two trees were damaged in a fierce windstorm and all the branches removed from the top of this one. In the few months it had vigorously re-asserted itself. Unfortunately, both trees are gone now so I couldn't compare them to the tree on my block

According to Jacobson, a black locust has showy white flowers while a honey locust has small greenish flowers; a black locust has 8 to 14 inch leaves with 9-25 leaflets while a honey locust has smaller leaves and up to 36 leaflets. Since there are neither flowers or leaves right now, I wouldn't be able to use these indicators until spring. Right now the tree is covered with lot of golden, bean-like seed pods. In a honey locust these should be 20" long and scarce, in a black locust, 2 to 5 ' long and abundant. My tree has abundant seed pods which made me think it's a black locust.

Then I found the lovely photograph above on Flickr and looked at the photograph of a honey locust on Wikipedia (did I say how much I love the Internet?). Now I'm sure my tree is a black locust. So I'm going to go add it to my observation list.

I also learned from Wikipedia (this time the article on black locusts) that the black locust is a major honey plant (bees love the fragrant flowers), it produces a wonderful hard wood used for fencing, railroad ties and firewood), it helps fix nitrogen in the soil (it's a member of the bean family and the seed pods do resemble bean pods) and it was named after the tree that supposedly fed St. John the Baptist in the desert, though, being native to America, it was not that tree. Jacobson says that black locusts have a beneficial influence on plants around them (unlike Black Walnuts which have a baneful influence). He writes: "Grass under locust trees is remarkably dark, green and lush." No wonder hugging my mascot tree has always inspired feelings of good will in me.

Jacobson, Arthur Lee, Trees of Seattle, Sasquatch 1989


Cathy said...

Black Locust is one of my favorite trees. I have been trying to find out how to buy one to plant in my yard, but it seems only the honey locusts are sold by nurseries.

I tried digging up a black locust baby tree one time - its roots are very shallow but spread widely - I must not have gotten enough of the root system as it did not survive...

Anonymous said...

Are you kidding me? Before you plant one, please note the nastiness of their thorns. a four inch thorn impaled itself through my child's wrist, and was embedded through the bone. It put my child in the hospital for three days, and had to be surgically removed. She is lucky to be alive and have use of her hand (after a month of physical therapy), as the thorn missed the major artery, nerves and tendons in her wrist and hand by only a fraction of an inch!

We are in the process of ripping the tree out of the yard. It's a slow process as the thorns can easily pierce gloves or shoes. That is one nasty tree!

Salem Willard said...

I believe the plant that would have fed John the Baptist would have been a false indigo, whose latin name is Baptisa. Also a member of the pea family, Baptisas fix nitrogen and produce bean-like seed pods, though they don't grow nearly as large as black locusts.