Juglans nigra
Black walnut
Common names: American walnut, Black walnut tree
At a glance
- Light
- Full sun
- Hardiness
- Hardy down to −30 °C
- Pruning
- Aug
- Harvest
- Oct
- Spacing
- 1000 cm, rows 1200 cm
- Water need
- Medium
Photo: R. A. Nonenmacher · CC BY-SA 4.0 · Source
This description was machine-translated.
Description
The black walnut is an imposing, fast-growing tree from North America with valuable, dark wood and small, intensely aromatic nuts. Like all walnut relatives, it releases the compound juglone through its roots and leaves, which inhibits sensitive neighbors such as tomato, potato, and apple. Therefore, plant it generously and alone.
Care instructions
Plant the black walnut in a sunny spot with deep, nutrient-rich, moist soil; it grows very large and needs space. Plant in autumn (November, week 44) and keep the root area moist for the first years. Harvest the nuts in October (week 42); the thick, coloring outer shell must be removed with gloves.
The care notes were machine-translated from German.
Garden year
HarvestOct
Soil & site
Soil pH
Soil type
loamy, humus-rich, well-drained, nutrient-rich, moist
The black walnut needs a deep (more than 80 cm of rootable depth), loose, nutrient-rich and well-watered loamy soil. Floodplain or deep loess soils are ideal. Sandy and heavy clay soils as well as compacted layers in the subsoil are unsuitable; the soil should be fresh to moist, and as a taproot tree it does not tolerate permanent waterlogging.
Feeding
Heavy feeder
Months
Mar–Apr
In the first years after planting, work mature compost shallowly into the drip zone each time in early spring (before shooting) and supplement it with horn shavings as a slow-acting nitrogen source. Over the years an occasional dose of compost is enough, as the far-reaching taproot system then supplies itself from the subsoil; keep nitrogen sparing overall, otherwise the shoots become soft and prone to frost.
Pruning
Your black walnut is a “bleeder” like the common walnut: prune only when necessary, and then in late summer (August) after the shoots have finished growing, because sap pressure is lowest then and winter or spring pruning leads to heavy sap loss. Established trees need no regular pruning. Limit yourself to dead wood and structurally dangerous branches.
Overwintering
Mature black walnuts easily survive Central European lowland winters without protection. They tolerate frost well below -20 °C. In the first two winters, protect young trees with hessian or coir on the trunk and a layer of leaf mulch over the root zone; late frosts in spring can damage the blossom, and only a warm, wind-sheltered position helps against that.
Propagation
Methods
- From seed
- Grafting
The easiest way to propagate black walnuts is by direct sowing: collect ripe nuts in autumn and plant them immediately, husk and all, about 8 to 10 cm deep in the soil. Protect the sowing area well from mice, because they like to eat the nuts. The first seedlings appear in spring. Alternatively, store the nuts mouse-proof and airy and cool until spring sowing; this replaces natural cold stratification. The wild species grows true to type from seed. Selected forms that are true to variety or especially high-yielding, as well as hybrid nuts (e.g. the varieties NG 23 or NG 38, crosses of Juglans nigra × Juglans regia), you propagate only by grafting, since seedlings do not reliably pass on the variety's characteristics. Juglans regia or Juglans nigra is suitable as rootstock. Grafting is done in winter or early spring, for example as cleft grafting or inverted-V grafting, and needs some practice and a warm establishment phase. Cuttings are not practical for black walnut in a home garden; rooting succeeds only rarely and unreliably, which is why this route is ruled out in practice.
Companion planting
Companion planting is partly traditional gardening lore. Where the reason is known, it is given.
For your garden
Grow Black walnut yourself
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