"Black Walnut"
Big Tree for September 2009
Several young American black walnut trees (Juglans nigra) grew in the yard of our first home in Pennsylvania. With young children our priority, shrubs and trees weren’t on our radar at the time.
We barely managed to rake up leaves in the fall and gather up the big black walnuts that fell on the driveway. These were both interesting and annoying. Black walnuts are messy, especially when they fall on the driveway and are run over by the car. The thick outer husk that turns from green to black as the nuts ripen is difficult to remove to get to the coarse woody shell underneath.
We had heard that driving over them was a real method of removing the husks, so we lined them up and crunched them with the car tires. It didn’t take long to figure out that picking up the mess of husks stains hands for days or weeks, and they have a strong unpleasant odor. To get the nutmeat, we tried cracking the very hard inner shell. This required a hammer, or a vise, and more mess. Finally, the tasty little pieces of nutmeat had to be carefully teased out with a nut pick.
All this work is well worth it, for the nutmeats have an unusual, distinctive, sharp taste, and are prized for baking. A local Pennsylvania recipe for apple pudding cake with black walnuts was truly divine, especially when one understands the time and effort to get the nuts out of the shell and then dried for cooking. I probably made it with black walnuts once – an absolutely elegant taste combination! English walnuts are tasteless in comparison, but because of their strong taste, black walnuts aren’t usually eaten raw.
I remember these walnut trees as unremarkable; just messy. They leaf out late in the spring with large frond-like, compound leaves that cast a light shade. Walnut trees are shade intolerant and the young trees that sprout in a good sunny location grow fast with tall, straight trunks, as they reach for the sun. In the fall, the leaves turn dull yellow and drop early. The whole compound leaflet detaches from the tree branch and the central leaf stems litter the ground with yet more mess.
Because of their high open canopy that cast little shade, I located my vegetable garden under two young walnuts trees, noticing that nothing much was growing under them. Little did I know that walnut trees have an allelopathic chemical in their roots, buds and nut husks, with some in the leaves, called juglone, that inhibits the growth of some plants.
Tomatoes and apples don’t grow well in their root zones. I can’t say that I noticed; maybe the tomatoes weren’t as vigorous as they might have been, but they didn’t suddenly wilt and die. While some trees and plants are affected when their roots intertwine with black walnut tree roots, many others are not, including red and sugar maple, dogwood, and trillium. Too bad that oriental bittersweet isn’t affected – I saw a young walnut tree being engulfed by bittersweet vines.
Because juglone is barely soluble in water and doesn’t move very far in the soil, there is little noticeable effect where walnut trees grow: lawns and woodland plants grow underneath them.
When growing in their favored sites with deep alluvial, sandy soils, walnut trees have huge root systems; both a deep tap root and a wide network of lateral roots that extend well beyond the canopy drip line. Like most nut trees they are difficult to transplant after two or three years. It is easier to plant a nut, but squirrels are good at finding them and gnawing through the shell to get to the tasty nutmeat.
New Hampshire is north of our native American walnut tree’s natural zone. But planted trees do grow well in the southern part of the state, and the nuts that begin to appear after the trees are about 20 years old sprout if not eaten by squirrels. Since there are some huge old walnut trees in New Hampshire that must be as old as the houses they are near, homeowners must have brought the nuts from the south and planted them for the nutmeats and to use for dyes, as well as the high shade and perhaps eventual lumber.
UNH Cooperative Extension’s Hillsborough County Forestry Educator Jon Nute notes, “The wood is very valuable where it is abundant in Ohio and Pennsylvania, but it is such an unusual tree in New Hampshire, it is not harvested commercially, but may be used by hobbyist furniture makers as individual trees are removed.”
One reason they are rare throughout their natural range is that the lumber from the long straight trunks is highly valued for woodworking and furniture making, especially for carving. Elegant, rich paneling is another special use because walnut wood doesn’t shrink or expand as much as other woods. Walnut gunstocks are classic.
The dye made from the husks and roots was and is prized for its rich brown hues, and also used with indigo to get black. No mordant is needed. It was used to dye wool, which may account for finding big old trees near farm houses today in New Hampshire. The hulls were also stewed up to make a brown ink that, along with a goose feather, provided rural folks with their means of communication and record keeping.
County champion black walnut trees are listed for five southern counties on the NH Big Tree list: nhbigtrees.org., click ‘The State and County Listing of Big Trees.’ Information about location and owners if located on private property is confidential and only available as needed by the state and county coordinators for updating records.
However if you know of a huge black walnut tree in your county, or if you live in a county with no champion and find one, call the NH Big Tree Coordinator: Carolyn Page, carolyn_page@hotmail.com, 603-664-2934, who will pass the information on to the appropriate county coordinator.
The UNH Cooperative Extension and the NH Division of Forests and Lands sponsor the NH Big Tree program in cooperation with the National Register of Big Trees through American Forests.
By Anne Krantz, UNH Cooperative Extension’s NH Big Tree Committee
