Plant, multiply black walnut use &

The black walnut can defy climate change in Germany. It impresses with its shady crown, its heat tolerance and its special nuts.

One could describe the black walnut (Juglans nigra) as the slightly more demanding sister of the walnut (Juglans regia). Because their demands - for example on soil or water supply - are somewhat higher. Thanks to its good heat tolerance, it can be counted among the future-proof climate trees. If the black walnut feels at home in its location, it grows quickly and is therefore an excellent source of shade for large gardens. This article explains everything you need to know about growing: from planting the black walnut to caring for and harvesting it.

Black Walnut: Leaves, Fruits and Origin

The black walnut belongs to the walnut family (Juglandaceae). It originally comes from North America, but came to us across the Atlantic as early as the 17th century. In recent years, their importance in Germany has once again increased significantly. It needs a warmer climate, is wind-resistant and not very susceptible to diseases and pests. For example, Juglans nigra can also be used in forestry as a substitute for less heat-tolerant tree species. A nice side effect: its fine, reddish-grained wood is decorative and in great demand.
The black walnut leaves are pinnate like those of the walnut, but the black walnut has up to 23 pinnate leaves instead of five to nine. These sit in pairs or unpaired on 30 - 60 cm long petioles.

Black walnuts are monoecious, so there are male and female flowers on one tree. However, self-pollination is prevented in most black walnut varieties by their dichogamy. This means that male and female flowers of a tree bloom at different times and therefore cannot pollinate each other. It is therefore necessary for a rich harvest that there is another black walnut variety with a different flowering time in the vicinity.

The infructescence of the black walnut looks similar to the well-known walnuts at first glance. On the tree, the nuts are still covered by a yellow-green outer shell that can be up to 6 cm thick. Only after the fruit has fallen from the tree in autumn does it begin to turn black and rot. This reveals the actual nut, which is thick-skinned, dark brown, grooved and ribbed.

Planting black walnut: location, time and procedure

The black walnut places high demands on its location. The soil should be rich in nutrients, deep, loose, slightly acidic to calcareous and well supplied with water. In addition, Juglans nigra likes to grow in sunny, warm and wind-protected places, such as are often found in wine-growing regions. Since black walnut trees usually grow to a height of more than 30 m and develop large, sprawling crowns, they need a lot of space - both above ground and below ground for the extensive and deep root system.
Once you have found a suitable location, you can start planting the black walnut go:

• Best planting time: April to November; Caution: Young trees are still sensitive to frost.
• Dig a comparatively large planting hole: at least 50 x 50 x 50 cm.
• If necessary, improve the soil with nutrient-rich potting soil such as our Plantura organic compost soil. Among other things, the high proportion of organic matter has a positive effect on the water retention capacity.
• Insert tree, set tree stakes for a connection.
• Fill the planting hole with a mixture of soil and nutrient-rich potting compost and press down well.
• Hit tree stakes even deeper, tie a stable connection.
• Form a casting ring out of excess soil and mulch the tree disc.
• Water generously and water regularly for the following weeks.

You can also grow a black walnut tree from seed, but then it will take at least 10 years before you can harvest the first fruits. The procedure is described in more detail in the section Propagating Black Walnut.

Tip: If you want to get a good harvest, you should also make sure that there are other varieties of black walnut in the vicinity. This allows the trees to pollinate each other.

Theproper care

The black walnut tree only needs a little attention in terms of care in the first years of growth, because then it is still in the critical phase of growth. So you should water the tree regularly in the first few years during longer dry periods and fertilize annually in spring. Our Plantura organic universal fertilizer, for example, is ideal for this, as it releases nutrients into the soil over a longer period of time and thus ensures a continuous supply of your black walnut.

Once the tree is older and well established, it usually no longer needs to be fertilized thanks to its large root system.
In the first few years, Juglans nigra can also be cut, but this is not absolutely necessary. You can use walnuts as a guide when cutting. The time should be in the summer, otherwise the black walnut will "bleed" profusely, i.e. it will transport water and nutrients out of the interface via the water-carrying xylem. Black walnuts must not be cut at the time of sprouting. Otherwise the cut can weaken them so much that they perish.

One maintenance measure that becomes more and more labor intensive with age is removing the leaves in autumn. The leaves contain a glucoside that is converted to juglone through microbial degradation and oxidation. Juglone is a so-called allelopathic, which inhibits seed germination and the growth of seedlings in the eaves area of the black walnut and can even kill lawns.

Tip: Like walnut trees, black walnuts can also be attacked by the walnut fruit fly (Rhagoletis completa), even if the pesky little creatures are usually only the destroy green shell. Nevertheless, you should collect and dispose of infested fruits, otherwise the larvae will pupate in the soil.

Propagate black walnut

Propagating black walnuts can be done in two ways: on the one hand by cuttings, on the other hand you can also try to grow trees from the nuts. Another possibility would be grafting, which is rarely crowned with success with the black walnut and is only carried out by professional tree nurseries.
Propagation via cuttings is usually much easier and faster.

Propagate black walnut by cuttings:

• Cutunwoody, he althy cuttings without fruit set between June and August.
• Young shoots on the black walnut tree that are at least 20 cm long are suitable as cuttings. The shoot tip is cut off after 15 cm. Even slightly woody shoots can still be used. It is also a good idea to select several shoots. This gives you a backup if one of the cuttings fails to grow.
• Put the shoots in planters that are filled with soil that is as nutrient-rich as possible. Our Plantura organic universal soil, for example, is ideal for this. If necessary, you can also place several cuttings in a planter.
• Press the soil firmly and water the cuttings well.
• The cuttings like it warm and sheltered, so a place with indirect sun is ideal. They should also be watered regularly, but waterlogging should be avoided at all costs.
• The cuttings should be wintered cool, but absolutely frost-free for the first few years. They are only winter-proof after about two years of growth.
• When the first new leaves form on the shoots, you can see that the growth was successful and the cuttings have taken root. Now the cuttings can move into their own pots. The following applies: the larger the pot, the larger the root system of the young black walnut plant. And the stronger and more robust it will be when planted in its final location.

Black walnut trees can also be grown from the nuts. You should use the freshest fruit possible, because the longer they are stored, the more their germination capacity decreases. You can try to sow the nuts about 5-8 cm deep in the ground directly in the garden. However, many nuts fall victim to the mice, which is why growing them in pots offers greater chances of success. Alternatively, you can also store the nuts cold in the refrigerator for 3 - 5 months over the winter and only sow them in the spring.

• In the fall, put some fresh nuts that you have removed the fleshy husk into a pot filled with potting soil and cover them with soil. If sustainability and biological quality are important to you when choosing the soil, you are well advised to use our Plantura organic herb and seed soil, for example. It is peat-free and even the packaging is Blue Angel certified.
• Ideally set thePlace the pot in a bright, sheltered place that is cool but frost-free.
• In the near future, the soil should be kept constantly moist, but without waterlogging, otherwise the seeds could become moldy.
• In the spring, the first shoots should appear, which shows the germination of the black walnut. Then the time has come to transplant the black walnuts. Now everyone gets their own pot, which can be filled with a slightly more nutritious substrate.
• The plants should be watered regularly and protected from late frosts.
• It is best to keep these young black walnut plants in pots for the next two years, so that they can be placed in a frost-free place for a short time in very cold winter temperatures.
• After two years the plants should be ready to be planted in place in the garden.

Harvest, effect and use: is the black walnut edible?

Black walnuts can be harvested in autumn. However, one should not pluck them from the tree, but wait until they fall down by themselves. Then they should first be freed from the green/black skin and then dried.

The black walnut is non-toxic and even very he althy. It's just not that easy to get hold of the edible black nuts. Cracking is hard work and usually cannot be accomplished with normal nutcrackers. But with a little creativity you will definitely find a solution, for example you can get at the nuts with a hammer. You should use cracked nuts quickly or store them as cool as possible, otherwise they will quickly go rancid. When using the black walnut, you can use other nuts as a guide. In America, where it is considered a delicacy, it forms the basis for pastries or ice cream, for example.
Some medicinal properties are also attributed to black nuts. For example, the nuts can have a blood pressure-lowering effect. The hard nut shells, which can be ground and then processed into tinctures, are real he alth miracles. These can be used externally for herpes or warts, for example, but they can also help with indigestion or high blood pressure, among other things.

Have some respectget before planting a black walnut tree in your yard? A good, slightly less demanding alternative is ordinary walnut trees. We have summarized everything you need to know about growing walnuts in a separate article.