Berberis thunbergii Seeds | Japanese Barberry
LATIN NAME: Berberis thunbergii
COMMON NAME: Japanese Barberry
Plant Profile
Japanese barberry is a dense, spiny shrub one to two metres tall, with small, spoon-shaped leaves that turn scarlet and orange in autumn and stay on the plant longer than those of most shrubs. The spines are modified leaves, single and sharp, and they sit at the base of each short shoot.
In spring the plant carries small, pale yellow flowers in clusters under the leaves, easy to miss, and by autumn these have become oblong red berries that hang on into winter. It is native to Japan and reached the West in the 1860s. Purple-leaved forms such as Atropurpurea are among the most planted shrubs in temperate gardens, and the golden-leaved Aurea and the dwarf Nana are equally common.
Science & Biotechnology
The species has become an unexpected subject in disease ecology. Work in Connecticut and New Jersey found that dense barberry stands harbour far more blacklegged ticks than adjacent forest, partly because the shrub’s humid canopy suits the tick and partly because white-footed mice, the main reservoir of the Lyme bacterium, shelter under it. Removing barberry lowered tick numbers and the proportion of infected nymphs, and the finding moved several states to restrict the sale of the species.
The plant also matters in alkaloid chemistry: its roots and stems contain berberine, though at lower levels than the European Berberis vulgaris, and the yellow colour of the inner bark comes from that same compound. The genus hybridises freely with Mahonia, and the two are now often merged, which has made the naming of garden plants unusually confused.
Uses & Benefits
In the garden the plant is used for low hedges, for winter structure and for autumn colour, and the purple and gold-leaved forms are planted as specimen shrubs. It clips well and tolerates dry shade, which is why it appears in so many municipal plantings.
That same tolerance is the problem. In the eastern United States it seeds into woodland and forms a thorny understorey that suppresses native ground flora, and it is now listed as invasive in a long list of states, with sales banned or restricted in several. Gardeners outside its native range should check local rules before planting. The berries are eaten by birds, which is how it spreads, but they are not for people: the alkaloids make the fruit unpalatable and mildly toxic.
Growing from Seed
Barberry seed needs cold and should be sown in autumn or stratified for three months at 4 °C. Clean the pulp off the berries first, because it inhibits germination and attracts mould, then sow into a gritty compost and cover with five millimetres of grit. Light is not required, but a cold frame helps keep the pans from drying out.
Seedlings appear in spring and grow slowly at first; prick them out when they are three centimetres tall and pot them on into a loam-based mix. Plant out in autumn at the same depth they grew in the pot, and water through the first summer. A hedge is best planted at 40 centimetres spacing and clipped in June, after flowering, so that the berries have time to form for winter colour.
Our Take
A tough shrub with fine autumn colour, but one to plant with care in North America, where it has escaped into woodland.
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