Black walnut
A wind-pollinated North American tree planted for valuable timber; it has no nectar but gives late-spring pollen and in some years aphid honeydew.
- Nectar
- None
- Pollen
- Low
- Flowering
- JanFebMarAprMayJunJulAugSepOctNovDec
- Height
- 20-30 m
- Life cycle
- Perennial
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Black walnut comes from eastern North America; in Europe and Turkey it is used in afforestation and park planting for its valuable timber. Its male flowers are long, hanging catkins and are wind-pollinated; it produces no nectar. Honey bees collect its pollen especially when other sources nearby are scarce.
Flowering
It flowers between late April and May, together with the leaves. The catkins shed their pollen within a few days.
Honey and pollen
It contributes no honey. In some years aphids leave honeydew on the leaves, which bees may collect, but a regular honeydew flow should not be expected.
Note for the beekeeper
Its roots and leaves release a substance called juglone that suppresses the growth of many plants beneath it; sowing bee forage under black walnut is unproductive. In some floodplain forests of central Europe it has naturalised and competes with native trees, so it is being monitored closely.