Connect the Dots: Black Locust Column

Published January 21, 2021 by the Vermont Community Newspaper Group

Q: How are black locust trees connected to other features in the landscape?

A: When I drive down out of the hills into the Champlain Valley’s lower elevations, I confess that I’m always keeping half an eye out for a very distinctive tree – the black locust. Its unusual bark is thick, heavily furrowed, and runs in sinuous lines, and the tree often grows in close clumps. As soon as I see one, I know I’m likely looking at a place with direct ties to the farm families of the early 1800s and indirect ties to some ancient, deep water.

Black locusts have very distinctive bark

Black locusts are not native to Vermont, but to the southern Appalachians and Ozarks. Although I often see them in front or side yards of an old house, they were not brought here as ornamental trees. They were imported around 1825 because they make excellent fence posts. Black locust wood is rot resistant in contact with the soil, and this unusual quality played a key role in a major Vermont landscape shift.

By the 1820s, Vermont farmers were transitioning from subsistence farming to commercial farming. Merino sheep were brought to Vermont, and farmstead after farmstead established pastures as they raised sheep for their high quality, marketable wool. Thousands of acres of new pasture required fencing, and the farmers looked at the best options available at the time. Field stone was used to build stone walls where it was abundant and stackable. Native white cedar was rot resistant but wasn’t common, and treated wood hadn’t yet been developed. Black locust fence posts ended up filling in the gap. 

Besides their rot resistance, farmers also liked black locusts because they easily regenerate themselves. They stump sprout, so if you cut the main trunk, side stems will sprout from the stump. They also root sucker, frequently sending up new stems from the roots a few feet out from the main trunk. It only takes 10-15 years for these root suckers to become fence-post size, far less than the multiple decades that white cedar needs to grow new post-size stems. 

The black locusts trees could be planted once, harvested periodically, and left to regenerate with almost no maintenance required. It’s hard to imagine a more ideal plant for busy farmers whose livelihood depended on keeping animals well contained.

By 1850, farmers in Vermont had mostly stopped planting new black locusts. The locust borer insect spread into Vermont and started to do significant damage to the trees. Farmers who had established clumps kept them, but new plantings were discontinued. So the clumps of trees we see today mostly date to the early 1800s.

Though virtually the whole state participated in the sheep boom, black locust trees are confined to distinct areas. In the Champlain Valley, their distribution pattern comes down to the effect of some ancient bodies of water more than 10,000 years ago.

 Glaciers had distributed stones generously across virtually all of Vermont as they advanced from the north. But a final chapter in glacial history made those stones unavailable to farmers in the lower elevations of the Champlain Valley. As the last glacier melted, the valley flooded miles wider than the present-day Lake Champlain, with first a huge freshwater lake and then a salt-water arm of the sea. This body of water sloshed for about 5000 years, and finally receded to the present Lake Champlain level about 10,000 years ago.  (The beluga whale skeleton found in Charlotte and now in the UVM Perkins Geology Museum dates to the saltwater portion.) Over these 5000 years, small clay and silt particles were thickly deposited on the lake and sea bottom over the earlier stony deposits. These small particles later formed today’s non-stony soils.  

From the Vermont Geological Survey, Major Glacial Lakes and the Champlain Sea, Vermont, 2020.

 The higher elevation areas of the valley above the high water level (the eastern halves of Hinesburg, St. George, and Williston, and a few scattered islands) have lots of stones in the soil which were used in the old stone walls. The lower elevation areas that were underwater (including most of Charlotte, Shelburne, and South Burlington, and the western halves of Hinesburg, St. George, and Williston) have almost no stones in their clay and silt soils, so black locusts were planted. So the distributions of black locusts and old stone walls usually don’t overlap.                

As I drive by black locusts on an old farmstead now, I think of them as touchstones to the past. I think about the farmer’s hand that planted the trees more than 150 years ago near their house or barn, and the bleating of many, many sheep. When I reach back even further, I imagine the deep water that once covered it all, and the whistling and clicking whales that were swimming over those future farmsteads.