By: Amy Grant
If you are an avid arborist or if you live in an area that was until recently populated by native black walnut trees, you may have questions about how to plant a black walnut tree. Also, what other black walnut tree info can we dig up?
Black walnut trees are native to the central and eastern United States and until the turn of the century, quite common. These trees can live to up to 200 years of age and are one of six walnut species found in the United States. In a natural setting, black walnut trees can be found growing alongside:
Intolerant of drought, black walnut trees have a lovely canopy, stretching up to 100 feet (30 m.) in height. Valued for their lumber, walnuts also provide food and shelter for native wildlife.
Black walnut roots, however, contain juglone which may be toxic to some types of plants. Be aware of this and plan accordingly.
The fruit husks from black walnut are used to make a yellow dye and the seed is used in candy making, abrasive cleaning products and explosives.
Consider planting black walnut trees if you live in USDA hardiness zones 5a through 9a with at least 25 inches (63.5 cm.) of precipitation and 140 frost-free days per year. Black walnut trees do best growing in deep, fertile, moist yet well-drained soil with texture ranging from sandy loam, loam, and silt loam to silty clay loam.
Select a site that is facing north or east when planting black walnut and avoid areas in valleys, bottomland sites or where airflow is minimal, as all of these foster potential frost damage. You’ll need to choose an area of full sun as well.
To grow your own black walnut, it’s best to either purchase a tree, get a seedling from a local gardener who has a tree, or try to germinate your own by planting nuts. Gather the nuts and remove the husks. Plant six nuts, 4 inches (10 cm.) apart in a cluster, 4-5 inches (10-13 cm.) deep. As you no doubt have squirrels, pre-emptive caring for the black walnut trees is in order. Cover the planting area with cloth and pin it into the ground. Lay a layer of mulch (straw or leaves) over the cloth to prevent repeated freezing and thawing. Mark the planting site clearly.
The seeds will germinate in the spring. Remove the mulch and cloth in late winter. Once the trees have grown for a few months, choose the best ones and eliminate the others. Caring for black walnut trees is pretty straightforward after that. Keep them moist until they attain some size. Otherwise, the trees, although drought sensitive, have a deep taproot and should be fine as long as they are situated as stipulated above.
This article was last updated on
Last Updated: July 21, 2020 References Approved
This article was co-authored by Andrew Carberry, MPH. Andrew Carberry has been working in food systems since 2008. He has a Masters in Public Health Nutrition and Public Health Planning and Administration from the University of Tennessee-Knoxville.
There are 14 references cited in this article, which can be found at the bottom of the page.
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While there are several species of walnut, most notably the black walnut and English walnut, basic planting and care instructions are all similar. Still, due to the existence of hundreds of varieties adapted to different climates and disease resistance, planting nuts from relatively nearby is recommended. Walnut trees can produce flavorful nuts and durable, attractive timber, but home gardeners should be aware that they often kill nearby plants! Also, keep in mind that walnut trees don’t start producing nuts until about 10 years after they have been planted and the nut production will peak at about 30 years after planting. You can plant walnut trees from nuts, which are often free to collect but tedious to prepare, or seedlings, which usually need to be purchased but typically have a higher success rate.
The black walnut tree (Juglans nigra) is one of North America’s most valuable and beautiful native trees, but it does have a “dark side.” Here’s what you should know before planting a black walnut in your yard—and how to harvest and eat the tasty walnuts, too!
The easily worked, close-grained wood of the black walnut has long been prized by furniture- and cabinetmakers for its attractive color and exceptional durability. Its logs are in such demand for veneer that “walnut rustlers” have made off with trees in the dead of night and even used helicopters in their operations.
The early settlers discovered black walnuts growing in mixed forests from Canada to northern Florida and west to the Great Plains. They found that its rich-brown heartwood was exceptionally resistant to decay and put it to use as fence posts, poles, shingles, and sills.
When surrounded by other trees in the forest, black walnuts grow straight and tall with few, if any, lower branches.
When planted in the open, the tree will branch out closer to the ground, developing a spreading shape that makes it easier to harvest its sweet, round, two- to three-inch nuts.
Settlers snacked on the nutritious walnuts out of hand, added them to soups and stews, and ground them into meal for baking the hard shells provided a perfect package for storing the nuts over winter.
Although the black walnut has many uses and benefits, the tree does come with a caveat: the black walnut’s roots, which may extend 50 feet or more from the trunk, exude a natural herbicide known as juglone. This substance is also found in the tree’s leaves and fruit husks.
Juglone does serve a purpose, though. It inhibits many plants’ growth under and around the tree, thereby limiting the tree’s competition, leaving more water and nutrients for itself.
Tomatoes, potatoes, apples, pears, berries, and some landscape plants such as rhododendrons, azaleas, and lilacs may be killed or stunted if grown in close proximity to black walnut roots or within the tree’s drip line (i.e., under the tree’s canopy). Plan your landscaping accordingly!
In spite of this, black walnuts make great shade trees for larger properties. They commonly grow to 50 feet or taller and about as wide, but specimens of more than 100 feet have been recorded.
Black walnut’s large, fernlike foliage provides light, airy shade for those grasses and ground covers not affected by juglone. In autumn, the leaves turn bright yellow, contrasting nicely with the tree’s rugged, dark bark.
Black walnuts require a deep, fertile soil with a near-neutral or slightly acidic pH. They are pretty much disease-free and are threatened by few pests.
Thud! Thud! Most walnut tree owners have a love/hate relationship because of the fruit which the tree drops in late summer though October. The size of a baseball and colored lime green, the fruit is quite heavy. It makes quite a mess and can be viewed as a nuisance.
Walnut tree owners will spend hours picking up the fruit some years. If you don’t remove the nuts, you’ll trip over them in the dark for the rest of the year (while they rot and mold on your lawn). Hire the kid down the street to pick up those the dropped walnuts (just be careful not to pay per nut—you’ll go broke)!
Photo Credit: John A. Anderson
If you’re willing to do the work of cracking the outer shell, the “meat” inside is edible, as the squirrels will attest squirrels have little problem chewing through the shells. (Note: Black Walnuts are different than the English Walnuts more commonly sold in stores and shown in the photo above.)
The sweet, earthy nutmeat inside is well worth the effort. Your grandparents may have harvested the walnuts which can be eaten raw or added to baking (cookies and bars). They can also be toppings on ice cream and cakes, enjoyed as a sweetened candy nut, or ground into meal for a unique flour.
To harvest, collect the nuts as soon as possible to avoid mold and remove the husks immediately. Wear gloves as the husks stain your hands (and anything they touch). If the nut is too hard, wait a few days and it will brown and soften up.) To remove the husk, you can simply step on them gently with an old pair of shoes. Hose down the nuts in a large bucket to remove any remaining husk.
Dry the walnuts for a couple of weeks on a screen or drying rack or in a hanging mesh bag. You can store them unshelled up to a year. Crack the shell with a hammer to get to the nut meat. (Strike at a 90-degree angle to the seam until the nut cracks). Use pliers to easily clip away the shell to release the nutmeat. Allow the freshly removed nutmeat to dry for a day before storing.
Do you have a black walnut tree? Please share your comments, questions, and advice!
Paul Alfrey from the Balkan Ecology Project covers the hows and whys of growing Walnuts – Juglans regia – https://balkanecologyproject.blogspot.com.au/2015/11/the-essential-guide-to-everything-you.htm
If I were to tell you of an apocalypse proof asset that is 100% guaranteed to increase in value, both in the short (3 yrs) and long term (300 yrs), will contribute to your good health, provides aesthetic pleasure to your surroundings, has the potential to replicate itself exponentially and has parts that can be dipped into smooth melted dark chocolate, covered in cocoa powder and eaten, surely you’ll be chuffed to learn that I’m referring to none other than Juglans regia – The Walnut tree.
The essential guide to everything you need to know to grow walnuts
At the moment I’m struggling to think of a better thing to do than to plant a walnut tree, other than to plant more than one walnut tree:) So here I present the Essential Guide to Everything you Need to Know about Walnuts.
During this article we’ll be focusing on the Persian Walnut – Juglans regia first providing an overview of the plant followed by advice on where to plant, how to care for, uses of walnuts and a look at some good companions plants for walnuts. We’ll also profile three productive and disease resistant Walnut cultivars that we are offering from our forest garden plant nursery.
Juglans regia is known by several common names including Persian walnut, common walnut, English walnut, Carpathian walnut and Madeira nut. The natural range of this plant is from the Carpathian mountains through the middle east and into the Himalayas.
Walnuts are fast growing trees that develop broad canopies reaching 18 m width and 30 m in height. It is a light-demanding species, requiring full sun to grow well.
A walnut compound leaf.
photo from – www.tree-guide.com/common-walnut
The buds awaken from winter dormancy in mid April – late May (depending on cultivar) and leaf fall occurs in early November. The large compound leaves give off a lemon /lime scent particularly when crushed. The flowers open before or around the same time as the leaves and you can find both male and female flowers on the plant (monoecious). The male flowers are slender catkins and the female flowers are smaller often found on the tips of the branches. Pollination is carried out by the wind.
Walnuts from the middle east and the Persian strains, are hardy to zone 5 (-23 °C) while the Carpathian strains can withstand temperatures as low as -32 °C (zone 4). You can’t grow these plants in the lower latitude areas without at least 500-1500 hrs per year of temperatures below 7 °C. At high latitude climate the young shoots and flowers are susceptible to frost damage in the spring, and early frosts in the autumn can cause damage to new shoots.
Walnuts have both male and female flower parts on the same tree (monoecious). The pollen is shed from the male flowers and should settle on the females flowers. The pollen is physically very small and light and can travel quite some distance. Studies have shown in certain orchards that wind blown pollen came from trees over a mile away.
Juglans regia – Female and Male Flowers
If the pollen from the male flower settles on the female flower at the point that they are receptive, fertilisation is likely to occur and the female flower will go on to develop into nuts. The time of pollen shedding from the male flower does not always overlap well with the time of female flower receptivity to pollen. This condition is referred to as dichogamy. To overcome this problem growers can select another walnut cultivar (a pollinator) the male flowers of which open at the same time as the female flowers from the main cultivar. The pollinator should be situated upwind from the main crop. If you have other walnuts upwind from your site you should not have problems with this.
Nearly all commercial orchards are co-planted with a pollinator variety to ensure the main crop gets enough pollen to set nuts. The recommendations for optimal pollination in an orchard environment is to plant one row of pollinators for every 8 main crop rows and to plant the row of pollinators upwind.
In some cultivars Walnut fruits form on the tips of the new seasons growth on other cultivars the fruit is formed on the lateral shoots.
Lateral bearing cultivars bear fruits on lateral buds of shoots and are generally of higher productivity than terminal and intermediate bearers due to the larger number of fruit buds on these plants.
Terminal bearing cultivars bear fruits on the tips of the shoots.
Tip bearing cultivar from a tree at our market garden site
Walnut trees commonly reproduce in the wild and are very easy to grow from seed. A tree grown from seed will start to produce fruit in 8 -12 yrs, it’s not certain that it will share the characteristics of the parent trees. Walnut cultivars are grafted and will start to fruit in the fifth year. Seeing as most cultivars are 2 yrs old when you buy them, the trees can start to bear fruit on the 3rd year after planting. (for expected yields see below)
Where to Plant
Location – The best locations for walnut trees are sunny, relatively sheltered sites. Frost pockets should be avoided.
Soil – The ideal soil is a deep, fertile, well drained loam with a pH between 6 and 7 (4.3 – 8.3 tolerated), although I’ve seen magnificent specimens growing in heavy clay on the river banks and trees tolerating a wide range of soil conditions.
Inhibitors – Walnuts produce a growth inhibitor – juglone – that has a detrimental effect on some species of plants growing nearby (negative allelopathy). Experimental studies have shown that juglone can inhibit plant respiration, depriving sensitive plants of needed energy and reducing the plants ability to uptake water and nutrients. There are many plants that do not seem to be affected by juglone (see below)
Comfrey ‘Bocking 14’ growing in the shade of a 20 year old Walnut
Walnut Pollination – When planting your walnut it’s important to consider a pollination partner if you would like to maximise your yields. (see above)
Fertility – It’s advisable to not add compost to the roots of walnuts when planting out and to add just a little top dressing compost to your newly planted trees. In the 2nd year, adding around 10 L of compost to the base of the tree in the spring will meet the plants growing nitrogen (N) demands. Too much N makes the trees more susceptible to Walnut Blight.
Irrigation – Should not be necessary unless rainfall is below 600 mm per year and is uneven in distribution throughout the year. In my climate in South-East Europe, Bulgaria I give my young trees 20 L once every two weeks during the summer months. Never use a sprinkler or hose to water and avoid splashing water onto the leaves as this will promote the development of Walnut Blight.
Weeding – Its important to keep the trees free from weeds whilst they establish as young trees are intolerant of competition especially from grass. Mulching the trees annually with card and straw will work well but take care to keep the collar free from mulch to prevent it from rotting.
Sunburn: can occur in excessive summer heat (38C) and the kernels can shrivel and darken. This is more so of a problem if the tree is under moisture stress.
Cold injury: Young trees are very susceptible to frost damage. Flowers can be destroyed in early frosts so it’s important to select late flowering cultivars if your planting site experiences early frosts.
Insect/Pest: Codling moth (Cydia pomonella), Navel orangeworm (Amyelois transitella), Walnut husk fly (Rhagoletis completa), aphids, scales and mites nematodes (Pratylenchus vulnus)
Disease: Blight (Xanthomonas campestris) blackline (cherry leaf roll virus) root and crown rots (Phytophthora spp., Armillaria mellea) deep bark canker (Erwinia rubrifaciens) crown gall (Agrobacterium tumefaciens).
Walnut Blight on our garden trees following an unusually wet spring and summer of 2013
Beyond the nutritious delicious nuts the other parts of the Walnut plant can be used for a variety of purposes.
Timber – The timber is very stable, hardly warps at all and after proper seasoning swells very little. The wood is straight grained, quite durable, slightly coarse (silky) in texture so easily held, strong, of medium density and can withstand considerable shock. It is easy to work and holds metal parts with little wear or risk of splitting. The heartwood is mottled with brown, chocolate, black and light purple colours intermingled. Some of the most attractive wood comes from the root crown area from which fine burr walnut veneers can be obtained.
Nuts – Nuts can be eaten raw, salted or pickled. Nuts must have an oil content of at least 50% to store successfully, nuts with 30 – 50% oil content have a higher moisture level and tend to shrivel in storage, so must be eaten immediately or preserved,
Oil – Can be pressed from the ripe nuts (sometimes over 50% by weight of kernels). The oil can be used raw, for cooking or as a butter substitute.
Leaves – Leaves can be used to make a wine.
Sap – The sap of the tree is edible, in the same way as that of the sugarmaple.
Medicinal uses – Several parts of the tree have medicinal uses. The leaves and bark have alterative, laxative, astringent and detergent properties, and are used for the treatment of skin diseases in addition the bark is a purgative. Leaves should be picked in June or July in fine weather, and dried quickly in a shady, warm, well ventilated place.
-The juice of the green husks, boiled with honey, is a good gargle for sore throats.
-The oil from nuts can be used for colic and skin diseases.
-The husks, shells and peel are sudorific, especially when green.
Other uses – The green husks can be boiled to produce a dark yellow dye the leaves contain a brown dye used on wool and to stain skin.
The oil has been used for making varnishes, polishing wood, in soaps and as a lamp oil.
The leaves have insect repellent properties in former times horses were rested underneath walnut trees to relieve them from insect irritation.
Walnuts uses section from Martin Crawford’s Agroforestry News Volume 1 Number 1 – Persian Walnuts
Walnuts grown from seed may not provide any nuts until they reach sexual maturity at 10 – 13 years of age. Grafted cultivars generally start to fruit in their 5th year. Most grafted cultivars are 2 yrs old so you can expect to receive the first crops in the 3rd year after planting. Below is a table showing the estimated yields of a walnut tree over time.
Walnuts, along with hickories, produce the chemical juglone, which is exuded from all parts of the plant. This chemical can inhibit the growth rate of nearby plants, a phenomenon known as negative alleopathy. This combined with the heavy water demands of larger trees and the deep shade cast in high summer presents challenges to effective companion planting but much can be grown in the under story during the first 15 – 20 years
20 yr old Walnut in our Garden with Sambucus nigra, Aronia melanocarpa and Pyrus cv. doing very well
Here’s alist of plants that have been observed to grow well under walnuts and are considered tolerant to Juglone. Bear in mind that few plants have been experimentally tested for sensitivity to juglone.
The plants highlighted in green are species I have personally observed growing seemingly unhindered in and around the under story of Juglans regia
Walnuts from our Gardens
Many factors affect sensitivity, including level of contact, health of the plant, soil environment, and the overall site conditions. Aside from juglone, a mature walnut will cast a very heavy shade and young sun demanding plants will not survive in these conditions. The list provided here is strictly a guide and should not be considered complete or definitive.
If you have experience of plants growing well under and around a Juglone producing plant that are not on this list, please share in the comments section below.
Below you can find profiles of some Bulgarian cultivars that we have on offer at our Bio-nursery. These cultivars are high yielding and resistant to common walnut diseases.
We are currently offering these cultivars at €22 per tree with 10% discount for orders over 10 trees. Delivery all other Europe
For other disease resistant walnut cultivars see Agroforestry Research Trust.
Walnut cultivars for Permaculture and Forest Gardens
Cultivar – ‘Izvor 10’
•Fruiting – The fruit forms on lateral buds and ripen around mid September. Excellent tasting oblong nuts with a thin shell. The nuts weigh around 10 g have a high fat content – 55.7%.
•Disease Resistance – Excellent resistance to Walnut anthracnose and Walnut blight
•Form – The tree forms a broad, relatively thin crown
•Hardiness – A very hardy cultivar tolerating temperatures down to -25 – 30 ºС
•Flowering Period – Late
Cultivar – ‘Sheinovo’
•Fruiting – The fruit forms on the tips and ripen around mid September. Excellent tasting nuts that are easy to remove from the thin shell. The nuts weigh around 12 -13 g and have a high fat content – 71.4% .
•Disease Resistance – Good resistance to Walnut anthracnose and Walnut blight
•Form – The tree is vigorous with a wide spread crown
•Hardiness – A hardy cultivar tolerating temperatures down to -24 ºС
•Flowering Period – Mid – Late
Cultivar – ‘Dryanovo’
•Fruiting – Fruits for on the tips of branches and ripen to very large 14 – 18 g round nuts. The fat content is 67.39%.
•Disease Resistance – Very resistant to anthracnose, though very susceptible to blight.
•Form – The tree is vigorous with dome shaped crown
•Hardiness – A hardy cultivar tolerating temperatures down to -24 ºС
•Flowering Period – Mid – Late
Not all plants are sensitive to the environment near the tree. But which ones are resistant? If you look at those that grow wild near volunteer juglone producers, you’ll have your answer!
When I look outside at the natural, wooded areas of my childhood home, I see plenty of these thriving – often within a foot or two of the trees in question.
Included in the “tolerant” category are the following trees:
These shrubs have been identified as resistant to juglone in soil:
The rest of the list can be accessed via the link referenced above.
You’re safe to grow these around your black walnut tree:
The list of flowering plants that can handle being planted next to black walnut is rather long. Enjoy these blooming plants and vines without worry:
Plus, there are dozens of others listed by the Penn State Extension.
These wonderful nut-bearers don't appreciate competition! Your new tree — whether it was planted as a seedling or has sprung from a nut — is going to have a hard time fighting for sunshine and nourishment if it's surrounded by fast-growing weeds. You'll need to mulch or cultivate to keep unwanted plants under control.
If your plot's vegetation is thick, cut and remove it in the fall, and plow or disk the area. Then, if you're planting seedlings in the spring, disk the site again beforehand, just as you would a garden. (You're going to have to keep the weeds down after your trees are in, too!)
More than 20 different species of moth larvae feed on black walnut trees, making it a valuable part of the ecosystem. Additionally, there are another 20 or so insects whose larva bore into the bark to feed. Chipmunks and squirrels will collect and bury nearly all the nuts, to use as food throughout the winter. In that regard they are valuable for our ecosystem. Also, by way of burying them they help propagate the species.
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