Introduced to France from America in 1601, the False Acacia is now naturalised throughout much of Europe, with many variants. It was introduced to England in the 1620s by John Tradescant the Elder, possibly from seed acquired from Robin, the French royal gardener, during the celebrations in France to mark the marriage of Charles I and Henrietta Maria. It is widely spread in southern England.
It is part of the pea family, seen in its leaves, flowers, pods and fixing of nitrogen, which allows it to thrive on poor soils. It grows to 10-15+ metres (30-45+ feet) with a large and irregular crown and soft green pinnate leaves emerging in early May. Hanging clusters of white, pea-like flowers in June become bunches of brown seed pods in the autumn. The bark is grey with long, deep fissures in it, making it easily recognisable even in winter. It is not good in windy locations as it has rather brittle branches which can break off easily. It grows vigorously.
Popular cultivars include Casque Rouge (profuse and highly-ornamental lilac-pink flowers) and Frisia, which rarely flowers but displays a golden yellow foliage from spring through to autumn. Frisia also tolerates dry conditions and copes well with reflected heat from buildings, so it is often seen in urban locations. However Frisia has proved susceptible to disease in recent years, failing to come into full leaf. The causes are unclear but may include leaf-spot fungus or honey fungus in the roots, and ultimately stress caused by recent wet weather (Robinia perform best on well-drained soils).
What’s not to like? Large thorns on either side of the leaf buds on its shoots, and proness to persistent, sometimes aggressive suckering. Its invasive habit means that planting is banned in Scotland.
What’s false about it? Its thorns mimic those of most acacia trees (thorn trees).
Where can you see them? Dulwich Park has a thriving colony of Frisias on its northern perimeter to the east of the Court Lane gates, one over 20 metres (65 feet) tall. (A sucker from the colony has grown rapidly into a small tree near the vegetable bed in my garden, where its own suckers are proving irritating).
One for your garden? Be wary - pretty they may be, but size, shading and suckering means that they’re not for smaller gardens, their neighbours or near buildings.
Jeremy Prescott Trees sub-committee
