By Robert Cox, Colorado State University Cooperative Extension, horticulture agent
While the black walnut tree is adapted to our area's soils and climate, you need to keep in mind a few things about this tree:
It grows large and eventually may provide too much shade for a small property. It's best not to think of black walnut as a landscape plant except on large properties. It really has few ornamental properties but does provide shade and nuts.
Walnut aphids are a regular insect pest.
Squirrels might become numerous and an annoyance.
All parts of walnut, including leaves, have an herbicide- like compound in them that inhibits growth of some other unrelated plants nearby, a sort of competitive advantage for the walnut. This phenomenon is called allelopathy.
The high value of walnut wood makes "walnut rustling" a problem where black walnut grows in forest stands or where it's planted as a timber crop. A few walnut-rustling cases have even been documented in urban areas where it was planted for the shade and nuts.
For more information, see Black Walnut Tree
Photo: Judy Sedbrook
© CSU/Denver County Extension Master Gardener 2010
888 E. Iliff Avenue, Denver, CO 80210
Date last revised: 01/05/2010