Black locust in bloom


Bordering my garden is a thicket predominated by black locusts (Robinia pseudoacacia, flowering below), willow seedlings, mulberry, and pernicious vines. Long ago I aspired to keep this area cleaned up to claim as part of the garden, though it’s outside my property. I’ve been mostly successful managing the long stretch of forest that borders the garden, but the area with the locusts and willows is constantly damp, and the wild seedlings and tangled vines have proven more than I can handle.

My goals have shifted to tolerate this weedy patch of trees, but to try to prevent them from encroaching further into the garden. A few times a year I chop back vines and stray mulberry branches, but I steer clear of the thorny locusts. For a few weeks in late April and early May my caution is rewarded with intensely fragrant, white wisteria like blooms that nearly make the black locust tolerable.

Years ago I was seduced by these splendid flowers to plant a somewhat domesticated cultivar of the locust, the yellow leafed ‘Frisia’. It grew vigorously, though it flowered more sparsely than the nearby natives. Finally, it proved too wild, seeding and suckering, and growing wide to occupy space reserved for a more precious Japanese maple. So, it was chopped out. Left behind were roots that suckered for several years until I dug and chopped out every remnant, and seeds that sprout ten years later.

When I read overzealous native plant enthusiasts lauding all plants native as mild mannered, low care, disease and pest resistant I chuckle over my battles with the locust. The woodline beside the garden is littered with trunks of locusts that have succumbed to disease, but not before seeding and suckering to spread this thorny thicket. So, the black locust is beautiful in flower, but has little ornamental value when not blooming, and is aggressive and short lived. Enjoy it in flower today along the roadside, but be cautioned against planting one in your garden. 

A considerably gentler native tree is the fringetree (Chionanthus virginicus, above) that flowers a week or two later than the black locust. It has no thorns, and doesn’t spread uncontrollably by seed or sucker. I’m quite certain that its only fault is that it flowers too briefly. At every other time of the year fringetree is unremarkable, but for a week in early May (late April this year) the small tree is covered in magnificent white, fringe-like blooms.

Fringetree is usually grown as a multi trunked tree or as a large shrub. Even when purchased as a single trunk tree it will annually grow a sucker trunk until you give up and let the tree have its way. Once an additional trunk or two is allowed the suckering ceases, so there is no danger that fringetree will spread itself through the garden. It is mild mannered, and other than a mild case of leaf spotting in a rainy spring, I’ve seen no pest or disease problems. If planted in a prominent location (and there’s no reason to plant fringetree elsewhere), this is the kind of tree that brings the neighbors over to ask “what is it”, and “will it live in my yard”?

5 Comments Add yours

  1. WDCgardener says:

    Amen! I have been fighting a neighbor’s Black Locust for YEARS! Hate that thing – was cut down two years ago and still sends out thorny suckers all over the garden 1/4-acre away – this thing will just not die – argh!

  2. I happen to ADORE black locust trees…. from a safe distance. There is one on a road where I often walk with my grand-nephew in his stroller, and I love standing underneath it, breathing deeply of that heavenly fragrance. It’s absolutely ENORMOUS, planted along a city street, and doesn’t seem to have suckered there at all (perhaps the surrounding concrete and asphalt have hindered such growth?).

    1. Dave says:

      I’ll admit to enjoying black locust. I went so far as to plant one, though I’ve admitted to my mistake and have remedied the problem. With a large enough property I’d be happy to plant the yellow leafed ‘Frisia’ again, but I’ve limited space, so when I’ve planted a thug it needs to be culled out.

  3. Richard Crisci says:

    Just had a chance to read your article on Black Locusts. How do you regard Honey Locusts?

    1. Dave says:

      Honeylocusts are fine tree as long as you are not expecting heavy shade from it. In my view, the dappled shade is a plus, and they are well behaved.

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