Juglans ailantifolia var. cordiformis
Heartnut
Common names: Heart Walnut, Japanese Heartnut
At a glance
- Light
- Full sun
- Hardiness
- Hardy down to −28 °C
- Pruning
- Aug–Sep
- Harvest
- Sep–Oct
- Spacing
- 800 cm, rows 900 cm
- Water need
- Medium
This description was machine-translated.
Description
The heartnut is a variety of the Japanese walnut whose nuts, when cracked, display a pleasing heart shape and often split into two clean halves. The tree is more robust and frost‑hardier than the true walnut, maturing later to avoid late frosts. Like its relatives, it produces juglone and should be planted away from sensitive neighbors.
Care instructions
Plant the heartnut in a sunny, spacious location with deep, well‑drained soil. Set it in the fall (November, week 45) and water regularly during the first few years. Harvest the nuts in September (week 38), remove the outer shell with gloves, and allow the kernels to air‑dry before storage.
The care notes were machine-translated from German.
Garden year
HarvestSep–Oct
Soil & site
Soil pH
Soil type
loamy, humus-rich, well-drained, nutrient-rich
You need a deep, well-drained and nutrient-rich loamy soil, because the heartnut does not tolerate waterlogging. Loose, humus-rich soil with good water retention is ideal; improve sandy soils beforehand with compost and give young trees an open, mulched root zone.
Feeding
Medium feeder
Months
Mar–Apr
In early spring before growth starts, spread mature compost around the root zone and work it in shallowly; alternatively, a dressing after the fruit has fallen also works. In the establishment years you can additionally add horn shavings as a slow-acting nitrogen supplier. Overall the heartnut is rather undemanding: feed moderately; older trees often need something only every two to three years.
Pruning
Prune the heartnut only when necessary, and then in late summer (mid August to end of September, from week 33): after the shoots have finished growing, the sap pressure is low and the wounds hardly bleed. Instead of shortening shoots, remove whole branches completely (thinning). An annual regular pruning is not necessary.
Overwintering
Established heartnut trees are fully hardy and need no winter protection in the Central European lowlands. In the first years, cover the root zone with leaves or bark mulch, and wrap the graft union of bought trees with hessian in the first winter.
Propagation
Methods
- From seed
- Grafting
The heartnut can be propagated in two ways, which serve different aims.
Sowing (seedling grown for yield): Harvest the ripe nuts in autumn and remove the green husk. Stratify the nuts cold and moist for about 90 to 120 days: lay them in moist sand or moist substrate and store them cool at about 2 to 5 °C (vegetable drawer of the fridge). From March to April, sow a few centimetres deep in deep pots or directly in an open-ground bed; after emergence, keep the pots in partial shade at first until the seedlings are well rooted. Important: seedlings turn out uneven: shell quality, ease of cracking and nut shape vary, even when the seed comes from a high-yielding, easy-cracking mother tree. Trueness to variety is therefore not guaranteed by sowing. You can expect the first nuts after about 3 to 5 years, and full yields only after several more years. Sowing is also suitable for raising rootstocks for grafting.
Grafting (true to variety): If you want to keep a particular variety (e.g. ‘Heartbreaker’) true to variety, only grafting achieves it. One-year-old seedlings of Juglans ailantifolia or Juglans regia serve as rootstock. The most reliable method suited to a home garden is hand grafting in spring before growth starts (roughly March to April): join scion and rootstock by whip-and-tongue grafting and keep the graft union warm at around 25 to 27 °C so that the wound heals well. Nut trees only callus reliably at this warmth. Alternatively, in high summer (roughly July), when the bark lifts easily, budding is possible: set a bud from this year's shoot precisely into the rootstock and bind it in so that air can pass. Grafted trees bear markedly earlier than seedlings.
Companion planting
Companion planting is partly traditional gardening lore. Where the reason is known, it is given.
For your garden
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