At a glance
- You prune the walnut only in late summer, mid August to mid September · CW 34 to 38. From January to May, it bleeds from every wound.
- Walnuts form at the tips of the shoots. Heading cuts cost you nuts, so you thin and redirect growth instead.
- The walnut tolerates large cuts poorly. The most important pruning happens in the formative years, the first ten.
- The sweet chestnut is tougher and even resprouts from old wood. You prune it in late winter, late February to late March · CW 9 to 13.
- The hazel is a shrub: each year, cut one or two of the oldest stems down at ground level. That is the whole job.
Nut trees are the great patient ones in the garden. A walnut takes ten years to reach full harvest, then bears for a human lifetime, mostly without ever seeing a saw. That is exactly why pruning goes wrong so often. Show up in March with the saw, because that is what you know from apple trees, and you will find a tree dripping from every wound for days.
This article explains why walnut and sweet chestnut react so differently to the saw, how you train a young nut tree, and what to do with an old one. The hazel gets a short section here; the full story is in Hazel in the garden.
Why the walnut bleeds in spring
The walnut (Juglans regia) builds up strong root pressure in late winter. Even before the buds open, it pumps water with dissolved sugars up into the crown. Cut off a branch during this time and that sap runs out of the wound, sometimes for days. This is called bleeding.
Losing sap alone will not kill a healthy tree. But a constantly wet, sugary wound is an ideal breeding ground for fungi and bacteria, and it cannot dry out and seal. By late summer, root pressure has dropped, the tree is in full leaf, and the wound starts callusing over right away. That is why you prune the walnut from mid August to mid September, and only then.
The one exception
You can remove dead wood at any time. A dead branch no longer carries sap, so it will not bleed, and falling branches are a real hazard on a large tree.
Cut back only into the dead wood, not into living tissue. You can tell dead wood by the missing buds, by bark that is flaking off, and by the fact that the twig snaps rather than springs back when you bend it.
Where the nuts grow
The walnut is monoecious: male catkins and female flowers sit on the same tree, but in different places. The male catkins hang from last year's wood. The female flowers, which become the nuts, appear at the tips of the young shoots that grow in spring from the terminal and upper side buds of last year's growth.
That means every shoot you shorten loses exactly the buds that would have produced nuts. So you never head back a walnut the way you would a young apple tree. You remove whole branches at their point of origin, or redirect growth onto a side branch, and leave the shoot tips alone.
Training a young walnut tree
The first ten years decide how the tree will look for the rest of its life. A walnut grows twelve to twenty meters tall and just as wide. Whatever you remove now as a thin shoot, you will not have to saw off later as a thick branch.
Set the trunk height
Later on, you will want to walk, mow, or maybe park under a walnut. So you remove the lower side branches year by year, until the branch-free trunk is about 1.80 to 2.20 meters tall. Not all at once: the lower branches feed the young trunk and help it thicken.
Keep one central leader
If two equally strong shoots compete for the top, remove the weaker one early. Co-dominant stems, two trunks of equal strength, tend to split apart in old walnuts.
Choose four or five scaffold branches
Above the trunk height, leave four or five well-spaced branches standing as the scaffold, ideally at a wide angle to the trunk. Narrow crotch angles with included bark are future breaking points.
After that, prune very little
Once the scaffold is established, you only prune deadwood, rubbing branches, and branches growing into paths, roofs, or power lines. The walnut shapes its own crown from there.
When you are crown lifting and thinning young trees, most of the branches sit between two and four meters up, too high for hand pruners and too thin for a saw. A telescoping pole pruner reaches that zone, and you stay with both feet on the ground instead of balancing on a ladder in late summer.
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Which variety, which site, and why a grafted tree bears earlier than a seedling: that is in Planting a walnut: site, final size, and variety choice.
Juglans regia
- Familie
- Walnut family (Juglandaceae)
- Standort
- Sunny, plenty of space, a site with little late frost risk
- Saison
- Pruning CW 34 to 38
- Wasserbedarf
- Moderate, deep soil
- Frosthärte
- Fully hardy, new growth at risk from late frost
The old walnut: little, and in stages
An old walnut tolerates large cuts poorly. Its wood compartmentalizes decay less well than oak, and behind a large cut surface, rot works its way into the trunk over the years. Cutting back the whole crown, the way you sometimes see on trees in a garden, does more harm than good.
If a branch really has to go, because it grows over the roof or threatens the garage, do it in late summer and ideally before it gets thicker than about ten centimeters. On large trees, where you would need a ladder or have to climb into the crown, an arborist using rope access is the better choice. That is not a question of courage, it is a question of the tree's stability.
Leaf spots and black nuts
Two diseases show up often on walnuts: Marssonina leaf blotch, with brown spots on leaves and husks, and bacterial blight, with black, sunken spots on young nuts. Both love a wet crown. Prune only in dry weather, remove infected leaves in autumn, and thin out crowded areas so the crown dries faster.
The sweet chestnut: the tough nut tree
The sweet chestnut (Castanea sativa) is, in many ways, the opposite of the walnut. It barely bleeds, tolerates pruning well, and even resprouts from old wood. In southern Europe, chestnut stands were coppiced, cut down at ground level, for centuries, and grew back vigorously every time.
The flowers, and later the fruit, appear on this year's shoots. So a winter prune does not remove the flowers directly, it only shifts where the new shoots grow. You prune in late winter, after the hard frosts, late February to late March · CW 9 to 13.
How you prune the chestnut
Training follows the same rules as for the walnut: one central leader, four or five scaffold branches, crown lifting the trunk step by step. After that, you thin every two to three years. Crossing, inward-growing, and dead branches come out, the rest stays.
You can rejuvenate an overgrown chestnut with small fruit over two or three winters by cutting old branches back to younger side branches. The chestnut answers with fresh wood and larger fruit.
Chestnut blight
Chestnut blight (Cryphonectria parasitica) enters through wounds and makes the bark split open, often with small orange pustules. Affected branches die back above the infection site. Disinfect your tools before and after every chestnut. If you suspect an infection, contact your regional plant protection service before you prune, because the pathogen is a regulated pest.
Everything about site, pollination, and harvesting the sweet chestnut is in Sweet chestnut and marron.
The hazel: a shrub, not a tree
The hazel (Corylus avellana) grows as a multi-stemmed shrub and bears on one-year-old wood. Pruning it is therefore a renewal cut from below: each year you remove one or two of the oldest, thickest stems at ground level. Six to ten stems of different ages should remain standing.
The best time is right after flowering in March, because by then you will not damage the female flowers, and that year's nuts have not yet set. If you have a Turkish hazel: you prune that like a tree, meaning hardly at all.
Prune the walnut in late summer, the chestnut in late winter, the hazel from below.
Nut tree rule
Set yourself a recurring task for the walnut in the last week of August. In your Gartenkern diary, you will not forget the short window, and over the years you will see how your tree's scaffold has grown.
Frequently asked questions
When do you prune a walnut tree?
In late summer, from mid August to mid September. From January to May, the walnut bleeds heavily from every wound because it builds up high root pressure. Only dead wood can be removed at any time.
Can you prune a walnut tree smaller?
Only to a limited extent. The walnut tolerates large cuts poorly, and rot forms easily behind big wounds. In late summer, you can redirect individual branches onto side branches. Keeping a tree that has outgrown its garden permanently small does not work. At that point, the site is the problem, not the pruning.
Why is my walnut tree bleeding after pruning?
Because it was pruned between January and May. During this time, the walnut pumps water with dissolved sugars up into the crown, and this sap runs out of every wound. The bleeding stops on its own once the leaves emerge. Do not put anything on the wound, and prune in late summer from now on.
When do you prune a sweet chestnut?
In late winter, after the hard frosts, from late February to late March. The sweet chestnut tolerates pruning well and resprouts from old wood too. Thinning every two to three years is enough.
How do you prune a hazel bush?
Remove one or two of the oldest stems at ground level each year, ideally right after flowering in March. Six to ten stems of different ages stay standing. That keeps the shrub young and bearing evenly.
Sources and further reading
- Bavarian State Institute for Viticulture and Horticulture (LWG), Bavarian Garden Academy: Walnut in the home garden. lwg.bayern.de/gartenakademie
- Julius Kühn Institute: Chestnut blight (Cryphonectria parasitica). julius-kuehn.de
- Plant database: Walnut, Sweet chestnut, Hazel
- In the magazine: Fruit tree pruning by fruit type, Harvesting, drying, and storing nuts, Pecan and heartnut
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