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The Monday Garden
Great Americans: The Locust Trees

Issue No. 100 - February 22, 2004
by Sue Sweeney

  
This morning, there’s a breath-takingly beautiful winter tree photo on my cousin Nancy’s site, and she mentioned our mutual love of winter tree viewing, so that inspired me to write about another fine winter-viewing tree, our native locust.
 
picture: Long Island Sound (Dolphin Cove, Stamford, CT)
 
North America has two great locust trees that range today from southern Canada to northern Florida. The Black (or Yellow) Locust (robinia pseudo-acacia) was pushed into Appalachia by the Ice Age but was spread back over the Eastern seaboard by the European settlers. The Honey Locust (gleditsia triacnthos) is a mid-westerner.
Both locusts, members of the pea family, leaf out late in spring and drop their leaves relatively early in the fall, which leaves their “bones” exposed for viewing a good part of the year. The spring leaf color is a lovely yellow green and the fall, orange to butter yellow. In summer, the Black Locust is blue green and the Honey, a bright green-green. The Black Locust has grape-shaped leaves; the Honey Locust leaves are more elongated.
 
picture: Honey Locust, Summer Street Stamford, Summer 2003
 
Picture: Morgan Street, Stamford CT, fall 2003
 
Both trees are urban, yard, and beach favorites. They are fast growers that need full sun but are tolerant of all soil types, salt and pollution. They’re subject to a range of icky pests (mites, virus, and fungus) but generally fight them off without help.

The Black is a tall, thin, gothic-looking tree with zig-zag twigs, no visible buds, and short thorns. It reproduces from roots suckers so it’s often found in groves. Older trees will have deeply furrowed bark.

 
picture: Black Locust, Bedford Street, Stamford, Ct
 
The Honey Locust has a rounder, spreading shape, big thorns, and the bark comes in large rough scales.
 
picture: Honey Locust, Morgan Street Ally, Stamford CT
 
The Black Locust has showy, white sweet-pea like flowers in late spring that, as any bee will tell you, make great honey. The Honey Locust’s flowers are white-green and not particularly noticeable. The both trees’ flowers turn into long, woody pods that the trees hold through winter. The Black’s look like polished mahogany; the Honey’s are lighter and tend to be very curly.

My mother has a Black that every other year produces an astonishing quantity of pods, despite the very young pods being a favorite of numerous birds. The squirrels and crows will eat the mature pods but only as a last resort. This, unfortunately, leaves bag after bag of pods to be raked up. The Honey Locusts, believe it or not, are named for a sweet, edible jelly found inside the pods, coating the seeds.

Locusts are great yard trees (if you get a pod-less, thorn-less cultivar). They grow fast so the nurseries can sell them fairly cheaply and they’ll give you lots of shade pronto. And it’s light shade so it’s OK for the shade garden and the grass. I have noticed that, over the years, the big, shallow locust roots heave up sidewalks and the like; indeed, the ones in front of my condo are doing a number on the driveway. So consider planting them away from paved areas where this could be a problem. Also, locust spread so fast that we have a local invasiveness warning out on them, so make sure to get the pod-less kind.

 
picture: Locust grove, Cove Island, Stamford, CT October 2003
  
From The Monday Garden. Copyright © by Sue Sweeney. Reproduced with permission. 

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