Walnuts are a highly desirable tree species for many reasons, including their edible nuts. In addition to producing valuable timber, they are a popular landscape tree in some areas. However, they can be a challenge to grow. Some of the most common problems encountered when growing walnut trees include sunburn, cold injury and diseases.
Seeds Need to be Stratified
For best results, walnut seeds should be stratified indoors or outside prior to planting in spring. This process allows the seeds to become accustomed to cold temperatures and moist conditions, which are necessary for germination. The process takes 90 to 120 days.
Stratification can be accomplished by placing seeds in a mixture of sand and peat moss. The sand and moss should be kept moist at all times.
Once the seeds have been stratified, they should be placed in a propagation mat and a cold frame. Water the seedlings regularly as they develop their first set of leaves. Move the pots to a sunny location outside when they are ready to be transplanted into their permanent home.
Planting the Tree
Black walnut trees should be planted bare-root about an inch deeper than their nursery pots to avoid frost heaving, which may push the main taproot upward and kill the tree. Be sure to space black walnut trees 40′ to 80′ apart and English walnuts 20′ to 40′ apart.
Prepare a Planting Site
A good location for a walnut tree is an open, sunny spot with well-drained soil. The tree will thrive in a wide range of climates and soil types. Generally speaking, they prefer well-drained loams with a pH of between 4.3 and 8. They are also known to tolerate heavy clay in some locations.
Prevent Nut Dropping:
One of the biggest issues associated with walnuts is that they often drop their nuts onto sidewalks and streets where they can contaminate other plants and human areas. They can also stain clothes and skin, especially if they get crushed.
Pruning:
Some people prune their walnut trees to encourage a healthier, taller and more robust plant. This can be done in early spring, before new growth has begun. This will help prevent the tree from getting leggy and tangled up in the growing canopy, which can be detrimental to its health and growth.
Soil Fertilization:
For a healthy, strong walnut tree, you should fertilize it at least once a year. For optimum results, have your soil tested to determine exactly which nutrients are deficient before applying a fertilizer. Then, use a slow-release nitrogen fertilizer with triple super phosphate and muriate of potash (about 3 pounds per tree) in late spring or summer.
The resulting plant will be stronger and more resilient to disease and insect attacks, making it a much more valuable resource for your property. You will also need to water the tree more frequently during its first growing season, as the soil becomes dry quickly.
Besides providing nuts, the trees can provide valuable shade and are excellent wildlife habitats. They can also be a useful source of mulch.