Alder buckthorn

Value to bees

Nectar

Very high

Pollen

Moderate

As a honey crop

Minor honey crop — a surplus only locally or occasionally

Which bees, and why

Worked steadily by honey bees and small solitary bees. Its most famous relationship is not with a bee at all — brimstone butterflies lay only on alder buckthorn and purging buckthorn, and the butterfly's distribution follows the shrub's almost exactly.

Very small fully open flowers with exposed nectar, accessible to the shortest-tongued insects.

Worth knowing

Very high nectar over a long window from an inconspicuous plant, and it is disproportionately important where damp woodland edge survives.

Flowering

In flower

May to July (northern hemisphere)

An unusually long flowering season for a shrub — flowers open successively over two months rather than in a single flush.

When nectar flows

Generous for so small a flower, and sustained by the long successive flowering. Honey bees work it steadily and it is a recognised minor honey source in parts of central Europe.

Year-to-year variation

Reliable on damp ground, and a minor crop where the shrub is abundant.

What it does to the honey

Where a surplus is taken, buckthorn honey is pale and mild with a faint green note. It usually contributes to a summer multifloral rather than standing alone.

Growing it

Conditions

Sun or part shade, damp acid to neutral soil. It thrives in wet ground where most hedgerow shrubs sulk.

Size

3-6 m.

Native range

Europe, North Africa and western Asia, on damp acid soils, fen carr and woodland edge.

Suits

Hedgerow, Large gardens, Meadow or wildflower area

• An excellent and much underused native hedge plant for damp ground, and the single most effective thing to plant for brimstone butterflies.
• The charcoal was historically the best available for gunpowder, which is a curious footnote for so retiring a shrub.
• Leave the berries — birds take them through autumn.

What it looks like

A thin open shrub with oval untoothed leaves and clusters of very small five-petalled greenish-white flowers in the leaf axils, followed by berries ripening green through red to black, all three colours often present at once.