Walnut trees: planting, pruning & care

Walnut trees are popular with many people, mainly for their delicious and nutritious fruit. Find out all about planting, pruning, and caring for your walnut tree.

Walnut trees are impressively large, very robust and undemanding. With enough space, a warm location, and a little patience, a walnut tree can be a great addition to any orchard or garden.

Walnut tree: origin and characteristics

Historically speaking, the common walnut tree (Juglans regia) originates from ancient Rome. Its botanical name Juglans regia is latin and is commonly translated to “Jupiter’s royal acorn”. The walnut tree belongs to the walnut family known as Juglandaceae and has been widely distributed not only in the warm Mediterranean region, but throughout Europe. Its love of warmth has been mitigated by cultivation, to the point that there are now private and commercial walnut tree plantations here in the UK too.

Walnut tree leaves are imparipinnate and consist of seven to nine individual leaves. Male walnut tree flowers are long and serpentine-like. Walnut trees are home to a remarkably long list of animals. They can reach 15 to 25 metres high when fully mature. With enough room, they can be of great benefit to humans and also animals such as squirrels, dormice, crows, rodents, and various insects. However, if you are short on space, planting a walnut tree in your garden may be prohibited due to its size, so check with your local authorities before planting.

The most popular types of walnut tree

There are several varieties of walnut trees: they differ in terms of growth, hardiness, ripening time, fruit characteristics and timing of budding.

There are several varieties of walnut trees that differ in terms of growth, hardiness, ripening time, fruit characteristics and when they come into leaf. The walnut tree varieties ‘Mars’ (Juglans regia ‘Mars’) or ‘Franquette’ (Juglans regia ‘Franquette’) are very hardy and not overly susceptible to late frosts due to their late leafing. Yield can be expected from grafted plants from just the third or fourth year in consistently high quantities. ‘Franquette’ is a slow growing variety. Other varieties that come late into leaf and are therefore also suitable for colder climates such as ours are ‘Buccaneer’ or ‘Broadview’. The varieties ‘Jupiter’ or ‘Esterhazy II’, on the other hand, are better suited to warmer locations due to their early leafing.

How to grow a walnut tree

When it comes to growing walnut trees, the ideal location is somewhere warm and sunny with plenty of light. Walnut trees also need enough space and plenty of distance from other trees, as they can develop quite a large crown. Very little grows in the places where the leaves and fruit pods of the walnut tree fall. This is due to the active substances it contains, which microorganisms convert into juglone, a toxic compound that can inhibit the growth of other plants.

Walnut trees prefer deep, well aerated, and nutrient-rich soil. The planting hole for a walnut tree will need to be at least 1.5 times as wide and deep as the walnut tree roots in the root ball. After digging the planting hole, fill it with mature compost or high-quality potting soil, such as our Plantura Organic All Purpose Compost and mix with the excavated soil. Our organic all-purpose compost is ideal for outdoors because it is safe for all garden animals and improves soil that is too heavy or too light.

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Next, tie the tree with one or two stakes, depending on its size. Finally, tread the soil around the trunk of your walnut tree down and water well.

The ideal time to plant a walnut tree is in the spring or autumn. This needs to be done after or before frosts occur, as the young plants are very sensitive to the colder temperatures. Planting your walnut tree in the autumn gives it ample time to develop fine roots, which are useful for absorbing water in spring and summer.

Walnut care: pruning and fertilising walnut trees

Walnut tree care is not difficult at all, as long as you observe a few important points regarding pruning, fertilising and watering.

Walnut tree pruning

Walnut trees do not generally require much pruning. You may need to prune your walnut tree occasionally when the crown and branches become very sprawling in order to maintain the tree’s shape and eliminate branches that compete with each other. To do this, only prune rubbing branches that are growing in the same direction or robbing each other of light or space. Avoid excessive pruning. To reduce the number of cuts and therefore wounds, prune branches in a single location. When there are two competing branches, select the branch that has the best branching angle and supports the optimal scaffolding in the canopy. Walnut trees often ‘bleed’ at the cutting points, so it is best to prune them between the end of June and the end of September. When pruning your walnut tree, avoid creating a horizontal surface as otherwise water can collect on the wound which could lead to rotting. Walnut trees are cut on the branch collar, so no stump remains. Generally speaking, walnut trees do not tolerate hard pruning. Old walnut trees should only be given a very limited rejuvenation pruning if at all due to the large wounds it creates.

Fertilising and watering walnut trees

During very dry conditions, you may need to water your walnut tree. It is especially important to provide young plants that have yet to develop a sound root system sufficient water in the first few months. Water them generously, but not often.

Walnut trees are very undemanding. They require very few nutrients and little phosphorus. Our Plantura Flower Food, for instance, contains relatively high levels of potassium and nitrogen, but comparatively little phosphorus, so is ideal for walnut trees. As these nutrients are mainly organic, they are released to the plant slowly. You can use compost as an alternative, but avoid using fresh rotting material as it is often far too rich in nutrients. A good time to fertilise walnut trees is after fruit fall.

Tip: Annual maintenance includes removing and disposing of leaves and old fruit skins. Diseases can spread from these in the coming spring if left.

Walnut tree propagation

You can propagate walnut trees via the nut. To do this, the walnut will need to be as fresh as possible and can either be put straight into the ground in its future location or in a pot. Outdoors, you often have problems with mice, so growing in pots is more promising. You will need to place the pot in a cold but frost-free location such as the balcony or a shed, as walnuts require a cold snap to germinate. In the spring, once you can see the first shoot, repot your young walnut tree into a new pot and give it fresh soil. When the late frosts are over, place the seedling in its intended location and water regularly.

It is also possible to buy plants that have already been grafted in specialist shops. Yields here are often more certain and predictable because the characteristics of the plants used are known. Grafted walnut trees can also bear fruit in as early as four or five years, whereas seedlings take a decade or more to bear fruit.

Another possibility is to propagate non-grafted walnut trees by mounding. To do this, cut off a young plant about a hand’s width above the ground and mound soil over the stump. In the best case, many small new shoots will form. Once these have taken root, they can be cut off or torn off and replanted in the ground.

When choosing a location, it is also important to note that non-grafted seedlings often grow in width and grafted walnut trees tend to grow taller.

Tip: You can also graft your own walnut trees, but it is somewhat more demanding and requires a little background knowledge as well as the right technical equipment.

Felling a walnut tree

If you plan to fell your walnut tree, check with your local authority beforehand for any local laws that may apply.

When to harvest walnut

Around September is harvest time for the walnut tree. When the fruit is ripe, the husk comes off and the familiar brown walnut appears. This is very brown in colour, which is why it is best to wear gloves and robust clothing for picking.

Due to their many nutrients, walnuts are a true superfood. They contain relatively high amounts of zinc, potassium, calcium, vitamin C and nutritionally valuable unsaturated fatty acids. You can either consume walnuts as they are, or use them for baking or as a fine flavourful addition to cooking. Walnut ice cream is also gaining in popularity. These nuts are a popular choice during the festive season.

Walnut tree diseases and pests

The walnut husk fly (Rhagoletis completa) is a common walnut tree pest and was recently discovered in Europe. It bites into the green husk to lay its eggs. The maggots then eat the flesh, which turns black. However, the nut itself remains intact except for a few black spots on the shell.

A common walnut tree disease is walnut leaf blotch, which occurs primarily in very wet weather. This can be caused by various bacterial or fungal pathogens. Severe infestation can cause the nuts to become unfit for human consumption and the tree to shed all its foliage before the fruit ripens. Some cultivars, such as ‘Sheinovo’, have resistance or increased tolerance to some leaf spot diseases.

Are walnuts poisonous?

Parts of the walnut tree can be toxic to animals such as horses. Some parts of the plant, such as the leaves, are harmless to humans, but these or the green husk can cause gastrointestinal problems or severe vomiting in sensitive people.

Walnuts are considered a superfood. This is due in part to their high zinc content. Discover more fruits and vegetables with a lot of zinc.