Black Walnut (juglans nigra)

Posted by Super User
on 01 January 2014

Black walnut is an North American form of walnut and perhaps the most adaptable species of its genus. It is an extremely valuable timber tree.

The black walnut is a large tree, often more than 100 feet in height, usually developing a full, well-formed trunk with high branches. The oval crown is quite open. The black trunk and stems add to its winter charms. The large, deciduous leaves are pinnately compound. Its nuts are edible but encased in a thick green covering that stains the skin, making harvesting difficult.

It is best to grow this tree from seed, since it has a deep taproot and resents transplanting. The black walnut is fast-growing in its youth, so it makes an interesting landscape specimen within a reasonable length of time, and then its growth slows down. It rarely reaches its maximum height of more than 100 feet in culture unless it is supplied with a deep, rich, moist soil. It also grows well, but slowly, in dry soils.

Due to its large size, the black walnut is best used as a specimen tree. Although tolerant of street conditions, it makes a poor street tree because of its messy leaves and fruit. All walnuts produce juglone, a substance that can be toxic to plants growing in their vicinity.

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