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Black Walnut Tree

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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

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Date last revised: 01/05/2010