Walnootboom

Juglans regia

Engels: Walnut Tree

fruitJuglandaceaeEetbaar

Walnootboom (Juglans regia) is a edible fruit plant from the Juglandaceae family that grows up to 25 meters tall. This plant thrives in full sun and requires low maintenance. Blooms in spring with green flowers and attracts birds.

Hoogte

1000–2500 cm

Breedte

800–1500 cm

Zonligging

full sun

Waterbehoefte

moderate

Grondsoort

loam, clay soil, chalky soil

Onderhoud

low maintenance

Bloeitijd

spring

Bloemkleuren

green

Ecologische waarde

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Verzorgingskalender

Taak	Jan	Feb	Mrt	Apr	Mei	Jun	Jul	Aug	Sep	Okt	Nov	Dec
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Care tips

Planting

Walnut trees thrive in full sun and need a sheltered position away from late-spring frosts, which can damage young shoots and flowers. Choose a site with plenty of space—mature trees reach 10–25 metres tall with a spread of 8–15 metres, so plant at least 10 metres from buildings, boundaries, and other large trees. Avoid planting near vegetable beds or ornamental borders; walnut roots release juglone, a substance toxic to many plants including tomatoes, potatoes, and rhododendrons. Walnuts tolerate a range of soils—loam, clay, and chalky ground all suit them—but drainage must be good. Waterlogged roots will rot. Dig a planting hole twice the width of the root ball and the same depth. Break up compacted soil at the base and incorporate a bucketful of well-rotted compost or manure into the backfill, but avoid adding fertiliser at planting time. Plant bare-root trees in October or November while the soil is still warm and the tree is dormant. Container-grown specimens can go in during the same period for best results. Position the tree so the soil mark on the stem sits level with the surrounding ground—planting too deep encourages stem rot. Spread the roots out naturally, backfill with the improved soil, and firm gently with your heel to eliminate air pockets. Water thoroughly after planting, applying at least 20 litres. Drive in a sturdy stake at a 45-degree angle to avoid the root ball, and secure the trunk with a tree tie, leaving room for growth. Apply a 7–10 cm layer of well-rotted compost or bark mulch around the base, keeping it clear of the trunk itself to prevent rot.

Pruning

Walnut trees require very little pruning and should only be pruned in late summer—specifically August or September—when the sap flow has slowed. Pruning in winter or early spring causes severe "bleeding" of sap from cut surfaces, which weakens the tree and invites fungal infection. Never prune walnuts between November and July. In the first few years, focus on developing a clear central leader and a well-spaced framework of branches. Remove any shoots growing from the base of the trunk and any branches that cross or rub against each other. Aim for an open, balanced crown with main branches spaced evenly around the trunk. Once the tree is established—usually after four or five years—pruning becomes minimal. Mature walnuts need only light maintenance pruning. In August or September, remove any dead, diseased, or damaged wood, cutting back to healthy tissue just above a bud or side branch. Take out any vigorous upright shoots (water sprouts) growing from main branches, as these rarely fruit well and clutter the canopy. If two branches are competing or crowding each other, remove the weaker or more poorly positioned one. Use sharp bypass secateurs for stems up to 2 cm thick and a pruning saw for anything larger. Make clean cuts at a slight angle to shed water. Avoid removing more than 10–15 per cent of the canopy in any one year. If a large branch must come out, consider hiring a qualified tree surgeon—walnuts are big trees and heavy limbs need safe handling. Resist the temptation to over-prune; walnuts fruit on wood that is two years old or more, so excessive cutting reduces your harvest.

Maintenance

Walnut trees have moderate water needs and tolerate short dry spells once established, but young trees need regular watering during their first two or three summers. From April to September, water deeply every 10–14 days if rainfall is scarce, applying 30–40 litres per session to encourage deep rooting. Mature trees rarely need supplemental watering except during prolonged drought. Avoid overhead watering; wet foliage encourages bacterial blight. Feeding is generally unnecessary. Walnuts grow well in average soil and excessive nitrogen promotes soft, frost-prone growth. If your tree shows poor vigour or pale leaves, apply a general-purpose granular fertiliser such as Growmore (7-7-7) in early spring at 70 grams per square metre around the drip line, but this is rarely needed. Mulch annually in late autumn with a 5 cm layer of well-rotted compost or bark, keeping it clear of the trunk. Walnuts are fully hardy across temperate Europe (zone 5a–9a) and need no winter protection. However, late frosts in April or May can blacken young shoots and flowers, reducing the crop. There is little you can do to prevent this beyond choosing a sheltered site. Pests are few. Walnut blister mite causes raised galls on leaves but rarely harms the tree. Aphids may cluster on new growth in spring; a strong jet of water usually dislodges them. The main disease concern is walnut blight (*Xanthomonas*), which causes dark, sunken spots on leaves, shoots, and developing nuts. Prune out affected growth in August and improve air circulation. Collect and bin fallen leaves in autumn to reduce overwintering spores. Harvest nuts in September and October when the green husks split and the shells inside have hardened.