About Black Walnut Trees
The Black Walnut (Juglans nigra) is a native nut tree that is found in the eastern half of the United States. While it is commonly known for its nuts, the wood from the tree has been used for furniture and other purposes since colonial times. The tree can grow to between 60 and 100 feet tall and usually lives between 150 and 200 years, but some have lived up to 300 years.
The bark of the black walnut is dark, with deep ridges that run down the length of the trunk. The leaves are pinnate, meaning they are divided into leaflets along a central stem. The tree produces small yellow flowers in spring before producing its fruit in fall. The fruit comes in clusters with each nut surrounded by a green husk that turns dark brown as it ripens in September or October. The husks contain a dark dye that can stain clothes and other surfaces if not handled properly.
The chemical juglone is produced by Black Walnut roots and may inhibit the growth of other plants around it.
The Black Walnut Tree has also been used as a natural treatment for parasites. These parasites include tapeworms and other intestinal worms that have infested the body. The use of ground-up hulls on the skin can help clear up certain types of acne and other skin conditions that may be caused by a parasitic infection.
Growing Black Walnut Trees
Black Walnut Trees have a taproot, so it’s best to plant them when they are young. Most Black Walnuts are propagated by grafting, so you will have to buy a sapling from a nursery instead of growing it from seed.
- Plant the black walnut in early spring as soon as the ground thaws.
- Dig a hole twice as wide and twice as deep as the root ball.
- Mix compost into the soil removed from the hole, and pour some water into the hole before adding the tree. Fill in with the enriched soil, and tamp down firmly.
- Water regularly until it becomes established, but make sure not to overwater since Black Walnuts don’t like soggy roots. After establishment, give it a deep watering once every week or two during dry conditions.
- Fertilize with a slow-release granular fertilizer according to label directions, or use composted manure on top of the soil around the tree every spring. Add mulch to help retain moisture and suppress weeds.
Caring Black Walnut Trees
If you love Black Walnuts and have decided to grow your own, congratulations. Black Walnut Trees are beautiful, but they’re not easy to grow. Growing Black Walnuts takes time and patience, but the rewards of a mature Black Walnut Tree are well worth the effort.
Black Walnuts are notoriously picky about the soil in which they grow. They like clay, loamy soil with a pH balance of 3.5 – 4. Most soil that has a pH balance of 6 or higher is too alkaline for Black Walnut Trees. Often this means that they need to be grown in raised beds filled with nutrient-rich soil that drains well.
Black Walnuts prefer full sun and do best when planted in an area where they will get multiple hours of direct sunlight per day.
If you want to plant more than one Black Walnut Tree, be sure you leave enough space between them for them to grow without crowding each other out. Each tree can grow as wide as it is tall and will need at least 50 feet in every direction to flourish.
Mulching helps keep moisture in the soil and keeps the roots of Black Walnut Trees cool during hot summer days. If you live in an area with harsh winters, mulch will also help protect your tree from freezing temperatures. A good layer of mulch 3 inches deep around the tree will help retain moisture and prevent weeds from growing around it.
Propagating Black Walnut Trees
The Black Walnut Tree is a valuable tree that can be propagated in the following ways:
Propagation By Seed
Black Walnut Trees can be grown from seeds. The outer shell of the seed must be cracked open to remove the inner seed, which should then be planted immediately. If you want to store the seeds over winter, they should be kept moist and stored at a temperature of 40 degrees Fahrenheit (4.5 degrees Celsius). After storing, they should be planted in the spring.
Propagation by Cuttings
Black Walnut Trees can also be propagated using cuttings from existing trees. Take a four-inch cutting from a twig on an existing tree and dip it in rooting hormone. Plant it in a small container with potting soil and keep it moist until the roots start to grow. Then plant it outdoors in a sunny area.
Pest and Disease Control
Black Walnut Trees are susceptible to a number of diseases and insect pests. To avoid problems, it’s important to know what they are and how to treat them.
Pest Problems
The most common pests attacking walnut trees are the walnut husk fly and the walnuts twig beetle. The impacts of these pests don’t become apparent until the tree is harvested. Walnut husk flies lay their eggs in the husks, causing fruit to drop before it matures. Walnut twig beetles carry thousand cankers disease, which cause dieback and gummosis. Preventing exposure to the diseases carried by these pests is the best way to protect your trees from them.
Black Walnut Trees are also susceptible to many such as aphids, mites, scale insects, and tent caterpillars. Aphids suck the life out of young walnut shoots and can cause distortion in the leaves. Mites are very tiny and barely visible to the naked eye. They feed on the undersides of leaves by sucking out the fluids. This can cause stippling on the leaves and webbing between branches. Scale insects attach themselves to branches, suck sap from them, excrete honeydew that encourages sooty mold growth, and make trees weak. Tent caterpillars spin webs in Black Walnut Tree branches, feeding on the foliage.
Treatment: Spray with insecticidal soap or horticultural oil (also called ultrafine horticultural oil).
Disease Problems
Several diseases may affect Black Walnuts. Bacterial blight causes yellowed leaves that wilt and fall off the tree. Phytophthora root rot is another serious disease, causing yellowing leaves and dieback. Prevention is key, as there is no cure for these diseases once they strike your tree.