Rat Poison - Dianella

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With elegant flowers and juicy-looking fruits hanging off the plant, Dianella (Dianella ensifolia) is a natural beauty to behold in the wild. But watch out! This beauty can be deadly – the plant’s toxicity is so high that it is made into rat poison!

Dianella, a perennial evergreen herb native to Hong Kong, is also found in southern and eastern China, tropical Asia and eastern Australia. The species is well known among Chinese society in various places, as revealed by the dozen aliases in Chinese.

In Hong Kong, Dianella is commonly found in the countryside. While it prefers warm and moist environments with abundant sunlight, it is tolerant of drought and shade.

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Sweetness with poison

During Dianella’s flowering and fruiting period in spring and summer, the flowers show off with its six perianth segments that are white tinged with purple - the outer three are sepals while the inner three are petals. In the middle, six brightly yellow stamens stand out. The small, elegant flower grows on a slender shoot, alongside the elongated sword-shape leaves, lending considerable resemblance to an orchid - hence earning it the Chinese name of “orchid”, but in fact, the species is a member of the Family Liliaceae.

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The fruits are even more dazzling! Each round berry is small, at about 8 millimetres in diameter. When the fruit ripens, it turns from green to a metallic purple blue that looks juicy and attractive. Beware: the fruit is poisonous! Botany tells us that a pulpy fruit evolves to attract animals for its propagation. But up to now we are still unclear whether there is an animal that feeds on the poisonous fruits, or if Dianella relies on other methods of propagation.

Poison as well as medicine

The whole Dianella plant is highly toxic. There have been reports of livestock deaths after consuming the plant. If people ingest it by mistake, breathing problems will occur that may become life threatening. In the past, people used the plant as rodenticide, by mixing the juice from the pounded rhizome and leaves with fried rice. Dianella is therefore known as “rat arsenic”.

On the other hand, Dianella is traditionally used as medicine to reduce inflammation and swelling. Nowadays, it is usually applied externally to avoid poisoning.