Walnut Trees: How to Grow and Care for Walnut Trees

Walnut trees (Juglandaceae) are deciduous trees that produce a stone fruit, or drupe, that houses edible kernels called walnuts inside their hard shells. They belong to the same family as hickory and pecan trees, which also produce edible nuts and buildable timber. These popular shade trees grow to heights upwards of fifty feet and can live for one hundred and fifty years. Walnut trees are monoecious, meaning they produce the male and female flowering blooms required to procreate. The trees are also slow growers, with mature trees producing edible walnut meats at a minimum of ten years.

Walnut trees produce a chemical compound called juglone which stunts the growth of neighboring plants. Be mindful when planting them alongside other growers because they may sap their nutrients, making it difficult for them to survive.

Here are some of the most popular varieties of walnut trees:

1. 1. Black walnut (juglans nigra): The black walnut tree, also known by the common name the American walnut, is a popular variety native to the United States. This tree produces nuts prized for their earthy flavor, and producers often harvest its timber for its hardwood. They thrive in USDA Hardiness Zones 4–9.
2. 2. Butternut (juglans cenerea): This variety, also known as white walnut, is similar to the black walnut, although smaller with a slower growth rate. It was once common in North America but has declined in popularity because canker disease wiped out most of this species on the continent. It grows well in Hardiness Zones 3–7.
3. 3. California black walnut (juglans californica): Native to Southern California, this variety can grow either as a large shrub or a small tree with a fork near the base of its trunk, making it appear as if two trees are growing in the place of one. It may be hard work to remove the fruits from this tree’s extra tough walnut shells. It grows well in Hardiness Zones 8–10.
4. 4. English walnut (juglans regia): Native to China, the English walnut tree is native to China. Also known as the Persian walnut, the tree’s walnut husks are thin and contain tasty nutmeat. As the tree matures, its bark goes from dark brown to a silvery gray. It grows well in Hardiness Zones 5–9.

Here are three of the most popular uses for walnut trees:

1. 1. Nut production: The most obvious use for walnut trees is to harvest their fruits for the edible nuts. Black walnut and English walnut are two varieties often used for harvesting.
2. 2. Lumber: Walnut tree wood is hard and hardy, and lumber from these trees can make everything from furniture and flooring to gunstocks. Black walnut is the most popular walnut tree used for lumber.
3. 3. Dyeing: The crushed shell of the walnut fruit, also called the husk, can dye clothing a brownish-gray color.

Growing walnut trees from seed requires patience, as they typically don’t begin producing good nuts until after a decade. You should also consider the effects of growing walnut trees in your garden because they can sap nutrients from other plants. Follow this step-by-step guide to growing a walnut tree from seed:

1. 1. Gather seeds. Gather fresh walnuts and remove the outer green skins from around their shells. Use walnuts from a tree growing in the wild, or buy them from the grocery store.
2. 2. Prepare the seeds. Wear gloves when handling walnuts, because they may irritate your hands. Soak your walnuts in a bucket of water for up to three days to soften their green outer skins so that you can peel them away by hand. You can also cut into their softened skins with a pocket knife. At the end of the process, you should have walnuts that still have their characteristic brown shells.
3. 3. Cold stratify the seeds. You will need to use cold stratification—forcing the seeds into dormancy by simulating winter conditions—to jump-start your walnut seed germination. To do so, place your nutshells in an airtight container or sealed plastic bag filled with moist peat moss. Store the container in the refrigerator for three to four months.
4. 4. Check for sprouts. After three to four months, your walnut seeds should have small sprouts that poke out of the top of their shells. When you see sprouts, remove the seeds from the fridge and keep them moist.
5. 5. Choose a planting site. Choose a planting site in your garden where your tree will receive plenty of direct sunlight. Prepare the spot with rich, well-draining soil, and clear the area of other vegetation and any large rocks or roots. Allow ample space for your trees to grow because they develop deep, twining root systems.
6. 6. Plant the seedlings. Plant your walnut seeds between two and three inches deep and tamp them down with soil. Space each seed at least twelve feet apart.
7. 7. Water the seedlings. Water your seedlings immediately after you plant them. Prepare to watch your walnut seeds grow into young trees, and mature in the years to come.

Here are some tips on caring for your walnut tree:

• Planting time: Plant your seeds in the ground in late September to make the most of your first growing season because this time of year still gives your tree full sun and allows for cold stratification. You can also plant your tree in late spring if you stratify your seeds ahead of time.
• Watering: Mature trees don’t need supplemental watering. However, in its first two years, it is helpful to water your tree at least once a week. Give your trees extra water as they establish themselves, especially if you’re growing them from seed.
• Weeding: Clear weeds from the area regularly if you’re growing your tree from a seed. Adding mulch to the soil around your walnut tree will also help keep the weeds away from your tree's root system.

The best time to harvest walnuts is between September and November. Here's how to harvest walnuts from your tree by hand:

• Don protection. Wear a pair of rubber gloves when harvesting walnuts to protect your skin from natural irritants in the nuts.
• Check for ripeness. Press your thumb against the walnut’s outer green skin. If the skin is tender enough that your thumbprint lingers for a moment, then the nut is ready for harvesting. Test walnuts from high up on your tree, as these ripen last and will indicate the ripeness of the rest of the tree.
• Shake loose. You can shake walnuts loose from your tree to harvest them once they are ripe. Use a pole or your hands to shake the walnuts loose and collect them from the ground immediately.
• Remove green skin. Remove the outer green skin with your hands or stomp on a group of fruits to break them open.
• Wash the unshelled nuts. Power-wash your unshelled nuts multiple times to remove any dirt, debris, or worms.
• Dry for a few weeks. Spread your unshelled nuts out into a single layer and leave them out to dry in a warm, dry place for a few weeks.
• Use a knife to hull the nuts. Use a paring knife, nutcracker, or pocket knife to hull the walnuts to reveal the nut inside once the shells are dry.
• Dry and store the nuts. Dry the nuts on a baking sheet for several days or toast them in the oven before eating. You can now store the dried, hulled nuts in an airtight bag at room temperature for up to a year.

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