Walnut trees can be great shade trees and a delicious food source. Many people love the nuts they provide in the fall, making them an exciting addition to your garden or landscape. To thrive, walnut trees need specific soil conditions.
In general, walnut trees grow best in rich loamy soil that is well-drained but holds some moisture. These soils occur in river valleys, streams, and other bottomlands. Walnut trees have deep tap roots, so the soil should be at least three feet deep before encountering gravel or bedrock.
Knowing the best place to plant your new tree is essential to tree ownership. Continue reading to understand the best soil conditions for your walnut tree!
Types of Walnut Tree
In North America, two walnut trees are actively planted in landscapes; the Black Walnut and the English Walnut. The trees have very similar needs with a few differences worth noting. Each grows in slightly different climates.
Black Walnut grows best in USDA Hardiness zones 4-9, and English Walnut grows best in USDA Hardiness zones 3-7.
According to the University of Minnesota Extension, the Black Walnut is also known as the Easter Black Walnut or American Walnut. This hardwood species is native to mixed deciduous forests in the eastern united states.
Black Walnut trees occur north of Massachusetts, south to Florida, west to Minnesota, and Texas. This tree can occasionally occur in southern regions of Canada.
The Black Walnut grows in USDA Hardiness zones 4-9. It is found alongside common trees such as sugar maple, silver maple, yellow poplar, oak, and beech. They will grow to 90-125 feet tall being one of the most giant trees in the North American forest!
Black Walnut Has Many Uses
The wood of the Black Walnut tree is prized for its exceptional hardwood used in construction and carpentry; it is one of the most expensive woods on the market.
Black Walnuts produce a round nut about two inches in diameter. They are single nuts enclosed by a hard outer green shell and fleshy husk that eventually turns black after the nut falls to the ground. When shelled, the nutmeat of the Black Walnut tree tastes richer and earthier than its English cousin.
Black Walnut trees are commercially available. We recommend planting a tree at least 12 inches tall and two to four years old! You can purchase one, like this Black Walnut Tree Sapling!
You can learn more about the differences between black walnut trees and other walnuts here if you’d like.
According to North Carolina Extension, English walnuts are not native to the United States but to Europe and Asia. This tree is cultivated for its sweet and white nut meat. It is smaller than the Black Walnut at only 40 to 60 feet tall.
In the united states, cultivated English walnuts have escaped their farms and become naturalized in some forests. It has a similar range to the Black Walnut tree and can grow in USDA hardiness zones three through seven.
If you’re interested in growing your own English walnut tree, take a peak at our article on how much fruit walnut trees produce – it’s a doozy!
English Walnut Wood Uses
It is grown for its wood, which is as hard as the Black Walnut tree, though lighter in color. Its nuts are sweeter than the Black Walnut, which is why this tree is most often cultivated for its nuts rather than its slightly more bitter cousin.
Despite the differences between these two trees, they have similar soil requirements and can be grown in similar locations, so for the purposes of this article, we will discuss their soil requirements together.
Best Soils For Walnut Trees
Both English and Black Walnut trees prefer moist, fertile soil to maintain a consistent growth rate. Soil should drain well and be medium to fine textured. Good drainage is a must.
Now getting to the good stuff – soil comprises particles of various sizes. These particles are generally sorted into three categories; sand, silt, and clay.
- Clay particles are the smallest and are prone to packing together tightly, creating poor drainage.
- Sand particles are the largest. Sandy soil drains quickly and does not hold water well, allowing air to reach plant roots easily.
- Silt particles lie in between and have some of the properties of both sand and clay.
The following soil types are ideal for walnut tree growth. Continue reading for more details on each.
- Sandy loam.
- Silt loam.
- Clay loam.
A loamy soil combines all three types of soil particles in equal amounts. This type of soil holds plenty of moisture while also draining well so air can reach the plant’s roots.
This soil is ideal for most plants, including the walnut tree. Loam may be ideal, but it isn’t the only type of soil in which a walnut tree can thrive.
A soil described as a sandy loam has all three types of soil particles but has higher concentrations of large sand particles. Clay particles are present but in small quantities.
This soil will retain some moisture but drain quickly and prevent soil compaction under normal conditions.
A soil described as a silt loam is at least fifty percent silty, with lower percentages of clay and sand.
Silt loam has excellent water retention but drains thoroughly between rains, allowing oxygen to reach tree roots.
A soil described as clay loam is less than 40 percent clay and 45 percent sand; the remaining particles are silt.
Clay loam retains more moisture than the other soils on this list, but the high percentage of sand still allows for thorough drainage.
Walnut Trees Need Deep Soil
In addition to having suitable soil for your walnut tree, you will want to ensure you have enough of it. Walnut trees form a deep taproot with a wide-spreading root system. This root system needs a lot of room to grow in search of water and nutrients.
Walnut trees have a deep tap root that requires at least three feet of loose soil before hitting bedrock, dense clay, or gravel.
If this deep tap root doesn’t have enough loose soil to grow into, your tree could die before it reaches maturity. Walnut trees need at least three feet of loose, fertile soil to become established.
The Best States To Plant A Walnut Tree
Both black walnut trees grow naturally in the Eastern United States. Since English Walnut trees require similar growing conditions to black walnuts, they can be planted in the same locations.
The best states for walnut trees:
- West Virginia
- North Carolina
- South Carolina
- Lower Michigan
- North-eastern Texas
- Southern Minnesota
- Southern Wisconsin
You can read more in our piece on the best places to plant a walnut tree!
The Best Climate for Walnut Trees
Walnut trees prefer a mild climate and cannot tolerate extreme heat or cold during the spring and fall. If the buds of the tree get hit with frost too early in the spring, your tree could end up damaged.
Walnut trees are sensitive to certain bacterial pests that are spread during times of early frost. Avoid planting your tree in any microclimate known for intense frost.
Walnut Trees Are Sensitive To Areas Of Drought
Similarly, walnut trees like to grow in moist soil. This makes them sensitive to hot areas because a drought could prematurely dry out the soil.
Even though a walnut tree prefers moist soil, soil that is too wet can be just as damaging as soil that is too dry.
Walnut trees do not tolerate sustained flooding for three or more days. Prolonged flooding keeps oxygen and other essential nutrients from being absorbed by the tree roots.
Walnut trees do not grow well in the shade. They should be planted independently, so they don’t have to compete for sunlight.
At most, a walnut tree can tolerate some dappled shade but should get full sun for most of the day. It takes a lot of sunlight to grow those delicious nuts!
Best Locations To Plant A Walnut Tree
The common factor among the soil types described in the section above is the ability to retain water while also maintaining appropriate drainage so that the roots of your walnut tree get the oxygen they need.
If you are unsure what kind of soil exists on your property, a few ecosystems are universally loved by walnut trees:
- Hardwood bottom lands
- Stream and river beds
- Low portions of north or east-facing slopes
- Low uplands
So if you’re aiming to plant a walnut tree – start with those spots!
Hardwood Bottom Lands
Hardwood bottomlands are forested wetlands near a river. These areas are characterized by periodic flooding, usually in early spring.
While hardwood bottomlands are excellent places for walnut trees, they can only withstand flooding for three to four consecutive days outside their dormancy.
Make sure your walnut tree does not have to endure flooding during the growing season.
Stream and River Beds
Streams transport sediment-rich nutrients to be deposited along the bank down steam. Since walnut trees love rich, moist soil, stream, and river beds are excellent locations for walnut trees.
Similar to bottomlands, streams and riverbeds are prone to flooding, which can damage a walnut tree. Ensure the site for your walnut tree endures no more than three to four consecutive days of flooding in the spring.
Low Portions of North or East-facing Slopes
Walnut trees grow well on north and east-facing slopes because these areas are not exposed to the hot afternoon sun.
These areas get sun early in the morning but remain shaded during the hot afternoon, ensuring the soil does not dry out. Walnut trees prefer moist soil with good drainage.
South and west-facing slopes get a bulk of the hot afternoon sun baking the topsoil. This phenomenon may cause the soil to dry out quickly.
Dry soils compact more efficiently, and do not allow for excellent water drainage or nutrient accumulation. This may be a good spot for a heat-loving tree or plant, but just not perfect for walnut trees.
Walnut trees need at least three feet of fertile topsoil to grow successfully. Higher portions of mountains or bluffs have shallow bedrock and are not great locations for walnut trees.
According to Purdue University, Uplands are the highest landscape parts, while lowlands are associated with rivers and streams.
Low uplands are the middle to lower portions of uplands where the topsoil is still deep enough to support a large walnut tree.
Low uplands make great locations for a walnut tree because the soil is rich in nutrients and relatively moist due to the drainage from higher portions of the landscape.
Terraces are the in-between layers in a landscape, between the uplands and the floodplains. Terraces usually form from an ancient glacial upwash that deposited nutrient-rich soil.
Soils that form from a previous outwash are well drained and deep enough for a walnut tree’s deep tap root, making them an excellent planting location.
Tips For Long-Term Care of Walnut Trees
Now that you know the best soils and locations to plant your walnut tree let’s review some long-term care tips to ensure your tree’s long, healthy life!
Caring for your walnut tree after planting can include:
- Pest management
After you have chosen the perfect site for your walnut tree and planted the tree with the addition of rich compost, you will need to control weeds for the first three years after planting.
This reduces competition for sunlight, moisture, and soil nutrients. It also reduces the likelihood of rodents making a home near your tree and possibly damaging the tree’s young bark. You can control weeds by mowing or applying a herbicide.
Young walnut trees should not need to be pruned unless you notice dieback. These trees are sometimes susceptible to disease, so if you notice a small area of your tree is not doing well, it is okay to prune it off.
Walnut trees are naturally able to grow straight and upright. As the tree matures, some pruning is acceptable. Generally, you will want to let your walnut tree do its own thing.
Always contact a professional if you are unsure how to prune a tree, or if you can’t tell what your walnut tree may need!
A healthy walnut tree planted in an appropriate location won’t need much watering through human intervention. The natural precipitation of the climate will provide plenty of moisture.
Newly planted walnut trees should be watered once per week along their drip line during their first growing season. Because walnut trees don’t like saturated soil, avoid watering too close to the trunk. After the first growing season, there is no need to provide supplemental water.
Drought is becoming more of a common occurrence these days. If you experience an unexpected dry spell, water your walnut tree deeply once per week. Take care not to overwater. Walnut tree roots need to dry out to access oxygen in between waterings.
If you have chosen the correct location for your walnut tree with moist, rich, well-drained soil, you will not need to fertilize your tree.
If your location isn’t among the four best walnut tree soils, you can fertilize with an organic, nitrogen-rich fertilizer such as Espoma Organic Tree-Tone.
Consult with your local arborist, or get your soil tested to find out what your soil may be lacking. Adding specific nutrients to the soil is better than guessing or adding too much fertilizer to your soil.
Too much fertilizer may cause an overgrowth of weeds. Young walnut trees do not like to compete for nutrients!
There are a few significant pests of black walnut trees. The most common are walnut caterpillars, bud borrers, and cankers. You may need to apply insecticides or fungicides to combat these problems.
Always consult an expert before applying insecticides or fungicides to your new tree. In most cases, it is not necessary to use heavy chemicals on a single walnut tree.
Hot Tip! Managing Juglone
English walnuts and black walnuts produce a chemical compound in all parts of the walnut tree (black walnuts produce more than English walnuts.)
This component is called Juglone and can slow down certain plant species’ growth This is the primary reason why people don’t grow black walnut trees.
Not all plants are sensitive to juglone. The most affected are members of the nightshade family, such as tomatoes, potatoes, eggplants, and peppers. Some common landscaping shrubs like lilac and hydrangea are sensitive to this compound.
If you plan to plant your walnut tree near your garden, it is best to look up what plants can be safely planted with a walnut tree without inhibiting growth.
There are no known exhaustive lists of plants sensitive to juglone; so here are a few that we’re akin to!
Common Trees Sensitive To Juglone
- Silver Maple
- Norway Spruce
Common Shrubs Sensitive To Juglone
If you notice your garden wilting, yellowing, or generally looking stunted, you may be experiencing a poor interaction with Juglone
The good news is that juglone breaks down quickly, so if you remove a walnut tree from your yard, you will only need to wait a few months before it is safe to plant in that space.
Remove the walnut tree, and wait one entire growing season. Your soil should be on its way back to normal but may take 5 years. For more information, check out our article about when to cut down your walnut tree!
Walnut trees are an excellent choice for many landscapes!
A Walnut tree can bring diversity, shade, and food to your yard! Walnut trees need nutrient-rich, moist, well-drained soil. They must be planted in at least three feet deep topsoil to allow room for the tree’s deep tap root.
Knowing the right location for a walnut tree will ensure you have a beautiful tree to appreciate for many years to come!
Best of luck on your tree-planting journey!
Desta, F., Colbert, J. J., Rentch, J. S., & Gottschalk, K. W. (2004). Aspect induced differences in vegetation, soil, and microclimatic characteristics of an Appalachian watershed. Castanea, 69(2), 92-108.
Islam, A. M., & Widhalm, J. R. (2020). Agricultural uses of juglone: Opportunities and challenges. Agronomy, 10(10), 1500.
Michler, C. H., Woeste, K. E., & Pijut, P. M. (2007). Black walnut. In Forest trees (pp. 189-198). Springer, Berlin, Heidelberg.
Ponder, F. (2004). Soils and nutrition management for black walnut. UNITED STATES DEPARTMENT OF AGRICULTURE FOREST SERVICE GENERAL TECHNICAL REPORT NC, 243, 71.
Strugstad, M., & Despotovski, S. (2012). A summary of extraction, synthesis, properties, and potential uses of juglone: A literature review. Journal of Ecosystems and Management, 13(3).