Dictamnus dasycarpus Seeds | Cortex Dictamni
LATIN NAME: Dictamnus dasycarpus
COMMON NAME: Dittany
Plant Profile
Dictamnus dasycarpus is an upright herbaceous perennial of sixty to ninety centimetres, with pinnate leaves that smell of lemon when crushed and pale pink flowers carried in a spike above the foliage. The whole plant is covered with glandular hairs that exude a volatile oil.
It grows in thin woodland and on stony slopes from north China to Siberia, and it is a plant of the dry edge rather than of the rich border. The flowers open in early summer and the seed pods that follow are heavy with the same oil, which is the source of the garden legend. It is slow to appear in spring and slow to die back, and a clump in a dry border can stand for twenty years without being lifted.
Science & Biotechnology
The oil contains furanocoumarins, chiefly dictamnine and psoralen, which intercalate into DNA and react with ultraviolet light. That is why handling the plant on a sunny day can leave a burn-like streak on the skin, and why the reaction appears hours later rather than at the moment of contact.
The burning bush story is partly true. On a still, hot evening the volatile oil that collects in the seed capsules can be ignited with a match, and a brief blue flame runs over the plant without consuming it. The flame is real; the bush does not burn, and the trick works only in still air and only for a second or two.
Uses & Benefits
The plant is grown in herbaceous borders for its early summer flower and its scent, and it is one of the few perennials that will flower in dry shade under trees. It is slow to establish and expensive to buy, which keeps it a collector’s plant rather than a bedding one.
In Chinese medicine the root bark, known as bai xian pi, is a separate commodity from the ornamental plant, and the two are graded and sold differently. The ornamental trade uses seed and divisions; the medicinal trade uses root bark from plants of five years and older, which is a different crop with a different economics.
Growing from Seed
Seed has a double dormancy and may need two winters to come up. Sow in autumn in a pot left outdoors, and do not throw the pot away after the first spring, since germination is often in the second year. A warm then cold then warm cycle breaks it most reliably.
Plant out in a sunny, dry position on alkaline soil, and do not move the plant once it has settled, since it has a deep taproot that resents disturbance. Water sparingly. Wear gloves when handling it in summer, and wash the sap off the skin before going into the sun. Mark the position with a label, since the plant dies down completely in winter and is easily dug by mistake.
Our Take
A slow, expensive, slightly dangerous plant for a dry border, and worth it for the scent and the seed heads. Handle it with gloves in July.
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