May 25, 2020

Killer Neighbor

Black walnut catkins

Pineo Photo - Black walnut catkins

Juglans nigra is not native to Maine but has been planted as an ornamental. Better known as black walnut, the tree has long been valued for its wood. According to “Forest Trees of Maine,” it is a rich, dark brown and takes a good polish, making it valuable for furniture, cabinets and gunstock.” As an ornamental, the tree can reach massive proportions, topping 100 feet tall, with wide-spreading branches. Black walnut produces nuts, of course, but you need to get to them before the animals do. It is not unusual to see squirrels wrestling the plum-sized nuts into their mouths and bouncing away with their prize. But for all its beauty, black walnut does not make an ideal neighbor. Its roots produce a substance called juglone that is toxic to a number of plants: Tomatoes to blueberries to apples may be injured or completely fail if planted within 50 to 60 feet of the tree’s dripline. Not all plants are susceptible, for we here at Garden Maine have a black walnut in our front yard and a number of species seem to thrive under the branches, including hosta and violets.

According to the Maine Register of Big Trees, there is a record black walnut in Limerick that has a circumference of 158 inches, a height of 100 feet and a crown spread of 87 feet.