Sunday, March 03, 2019

Black Locust


Weather: Rain Saturday evening; drive is still spongy underfoot and wheel barrow is still leaving ruts in saturated soil sitting above frozen ground.

Last useful rain: 3/2. Week’s low: 11 degrees F. Week’s high: 65 degrees F in the shade.

What’s green: Leaves on juniper and other evergreens, Dutch iris, grape hyacinth, vinca, snapdragon, blue flax, winecup mallow, hollyhocks, sweet peas, anthemis, dandelion, needle and cheat grass

What’s gray, gray-green, or blue green: Four-winged saltbush, winterfat, snow-in-summer leaves

What’s red or purple: Stems on sandbar willow and bing cherries; new wood on peaches and apples; leaves on coral bells, alfilerillo, golden spur columbine, coral beards tongue, purple aster

What’s yellow: Stems on weeping willows

Tasks: Spent more time removing soil that slide from a bank into my drive. Each day I removed a little, then let the sun thaw some more for the next day. Many of the rocks I put down in a saturated path sank so only the tops are visible. They’re enough to keep me out of the mud.

Animal sightings: Small birds.


Weekly update: The black locust has been a problem since Megacyllene robiniae larvae first attacked it in 2007. Adult longhorned beetles feed on goldenrod, then lay their eggs in tree trunks. Come spring, the eggs hatch into locust borers that eat the wood. By the time you see a pile of sawdust at the base of the tree, it’s too late. Each year, sometime in June or early July, a trunk has fallen, usually into my drive.

The first man I called to remove a fallen branch said borers weren’t unusual, and the tree wouldn’t die. He added some farmers used to use the regrowth for fence posts.

The first few years I tried to get the fallen branches removed before August when the pupae hatched into beetles. That didn’t help, so I waited until winter to call a tree trimmer. Then I could have him prune other trees while they were dormant.

When I first had the problem, I removed my goldenrod plants. Since the insects came back, I decided there was no reason to forego the yellow flowers.

In July of 2012, the man I called told me winds the previous week had taken down a lot of branches. He also said a number of people were having problems with the black locusts and that people who had them near their houses were having them removed, especially the really big trees. I’m not sure if that meant the locust borers were a new problem or not.

I saw some adult beetles for the first time in September of 2017. In October, I heard a red-headed woodpecker in the tree. It didn’t help. Three trunks came down last year.


Each year when a trunk came down, the locust put out one or two new ones. They moved over to a soaker hose I had and destroyed it by squeezing it. Last summer there were so many branches, they began infringing on other shrubs.

This winter I decided to have everything cut down, in hopes that would remove the borer eggs. After the tree trimmer left, I went out and removed the leaves and duff around the stool. I hoped to remove any eggs that might have fallen. When it gets a little warmer I may put down one of those poisons that kill grubs.

I know it will come back. Suckers I cut to the ground, always return. I haven’t decided how much new growth I’m going to let grow. I’m thinking I may try to return to a single tree, instead of the copse I had. As I expect many suckers will come up, I should be able to select one that won’t be in my way. The thorns are a nuisance when the branches grow into my pathways.

Or, once I get used to the bare spot, I may just keep them all cut down. While the legume flowers are fragrant when they bloom, the buds or flowers usually are killed by frost. I’m not sure they’re worth the cost of a tree trimmer every winter.


Notes on photographs:
1. Black locust (Robinia pseudoacacia) trunk fallen over the retaining wall, with the Dr. Huey roses that grew up into it. 5 June 2016.

2. Leaves and sawdust at the base of the tree. 8 June 2008.
3. Black locust stumps after it was cut down. 3 March 2019.
4. Damage in to wood of a trunk. 14 February 2019.

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