Did you know that one of the most valuable trees in North America is located at Hawk Valley Farm?
Black Walnut (Juglans nigra) has been an important tree species since it was first discovered by early settlers. The decay-resistant wood was used to make fence posts, poles, shingles, and window sills according to the Old Farmer’s Almanac. Native Americans and settlers also used the nut hulls to make dye, ink, and medicine. Today, its strong, beautiful wood is still valued in making furniture, cabinets, and veneer. The edible nuts, which are usually ripe by mid-autumn, are enjoyed by people and many other animals — especially the squirrels and chipmunks at Hawk Valley Farm!
Habitat:Juglans nigra can grow in open areas or in forests, and each location will impact its growth habit. With open space, it will have more of an open, low-branching crown and spread almost as wide as tall (up to 75′). In forests, it will grow taller (up to 150′) and self-prune its lower limbs. It prefers full sun and moist, rich soils like those of Hawk Valley Farm. (This prime agricultural soil is currently being studied by UMass Lowell students!)
Form & Function: Black Walnut trees develop a deep taproot along with other wide-spreading roots. You may notice that few plants grow under Black Walnut canopies. This is due to the chemical called juglone produced by the roots and almost all other parts of the tree. Juglone acts as a natural herbicide, limiting competition from particular plants, so more water, light, and nutrients are available for the Black Walnut– a smart adaptation and survival strategy.
Its long 1-2′ leaves are pinnately compound, with 9-23 dark green leaflets arranged along the stem. These leaflets are 2-5″ long and finely-toothed; turning yellow in autumn. The juglone also defends the leaves from fungal pests, helping the tree stay strong and healthy. Another chemical in the leaves, ellagic acid, is effective in removing carcinogenic hydrocarbons from the air, thereby reducing the effects of air pollution. (Source)
Fruit: Two layers protect the walnut or kernel inside. A green or brown fleshy sphere (husk) envelops the hard, black inner shell. The shell is thick and corrugated, protecting the oily, sweet nut. It can take 12-15 years for a tree to first produce nuts.
Faunal Associations: Besides the nutritious seeds that are consumed by many animals such as woodpeckers, turkey, fox, bears, raccoons, and eastern grey and red squirrels, the leaves are extremely valuable to certain insect species that have co-evolved with this plant. The Walnut Caterpillar specializes on Black Walnut and others in the Juglandaceae family, meaning these leaves are the only food these caterpillars can eat to survive. Over 100 species of moths and butterflies, including Luna Moths and Banded Hairstreaks, consume the leaves of Black Walnut according to renowned entomologist, Douglas Tallamy.
The value of mature Black Walnuts is immense– from food to furniture to storing carbon.
How many Black Walnut trees can you find at Hawk Valley Farm ? Let us know!
(originally featured as October 2020 Flora & Fauna Friday)
