Arisaema erubescens Seeds | Rhizoma Arisaematis
LATIN NAME: Arisaema erubescens
COMMON NAME: Arisaema Rhizome
Plant Profile
Arisaema erubescens is a woodland aroid of central and south-west China, growing from a flattened rhizome that sits just below the leaf litter. In spring it sends up a single leaf divided into many leaflets and a separate flower spike, the spadix, wrapped in a spathe that is green outside and often purple-striped within.
The inflorescence is the curious part: a hooded tube with a narrow opening, and inside it a stalk of tiny flowers, male at the top and female at the base on the same spike, or one sex only on a given plant. The fruit is a head of red berries in autumn.
Science & Biotechnology
The genus is famous for changing sex. A plant that has stored enough energy in its rhizome produces female flowers; a smaller one produces male flowers; a plant with very little reserves may not flower at all. The switch is a response to size rather than to age, and it can go back and forth over successive seasons.
Pollination is by flies and small beetles that are attracted to the smell of the spathe, which in many aroids mimics carrion or fungus. The plant is toxic: all parts contain calcium oxalate crystals and, in some species, free oxalic acid, which cause immediate burning and swelling of the mouth if chewed. The berries are eaten by birds, which spread the seed, and the red colour is a signal rather than a warning to them, since birds are not affected by the oxalate in the same way as mammals.
Uses & Benefits
The dried rhizome is used in Chinese medicine under the name tian nan xing, processed to reduce toxicity before use, and it appears in formulas for cough and for phlegm. Raw rhizome is dangerous and has caused serious injury when eaten by mistake.
In the garden the plant is grown for its architectural flower and its mottled foliage, in shade and in moist leaf mould. It is also one of the few aroids hardy enough for cold woodland gardens, and it naturalises slowly where it is happy. Handling the cut rhizome should be done with gloves.
Growing from Seed
Seed should be sown fresh, since it dies if dried, and it needs a cold period to germinate. Clean the pulp from the berries, sow in a shaded frame in autumn, and expect seedlings in the second spring. The rhizome can be divided in late summer, when the leaf has died down.
Plants want deep shade, humus-rich soil and steady moisture in spring, followed by drier conditions in summer when the leaf dies back. Mark the site, since the plant disappears completely by midsummer. They are slow to bulk up and resent disturbance, so a clump should be left alone for years.
Our Take
A woodland curiosity with a strange sex life and a genuinely dangerous sap, worth growing in shade and worth handling with gloves.
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