What is a Fortnight Lily?

R. Britton

A fortnight lily, or Dietes iridioides, is a species belonging to the Dietes genus. It previously was classified in the Morea genus, but this was changed because of the ability of this species to reproduce using rhizomes. Rhizomes are fibrous tendrils that spread away from the plant beneath the ground. Periodically, a shoot ascends from the rhizome to form a new plant above the surface.

Fortnight lilies are native to Africa.
Fortnight lilies are native to Africa.

The fortnight lily is native to Africa, hence it is commonly called the African iris. Although endemic to Africa, where it still grows in abundance in the wild, the plant has been introduced in many parts of the world and is a very popular garden plant. Despite its popularity, the fortnight lily can prove to be problematic in gardens because it spreads and grows rapidly. Its ability to reproduce via seeds or rhizomes can make this plant incredibly difficult to control, because it will spread and grow amongst other plants, such as rose bushes, and then it becomes very difficult to remove it without damaging other plants.

There are parts of the fortnight lily that are toxic and can cause stomach pain or other digestive issues.
There are parts of the fortnight lily that are toxic and can cause stomach pain or other digestive issues.

The fortnight lily prefers full sun and a regular watering pattern to maximize flower production. Although the plant can tolerate periods of little water, strong winds and even freezing temperatures, it should be noted that it will not tolerate over-watering. The foliage of the fortnight lily is evergreen, and it grows long, tough, sword-like, dark green leaves that stand erect in a fan shape.

The flower stalks can grow to 4 feet (1.2 m) in optimal conditions, and produce flowers successionally. The flowers, once in bloom, usually last for only one day. To limit the ability of the fortnight lily to reproduce, it is advisable for one to remove dead flowers before they dry out and produce seeds, which will disperse with the wind and germinate.

Parts of the fortnight lily are toxic, and can cause stomach pain, vomiting and diarrhea, and skin irritation might occur after the plant is handled. It therefore is important for one to wash his or her hands immediately after handling this plant. Traditionally, despite the plant's toxicity, in parts of Africa, the plant has been prepared and used to treat conditions such as dysentery, to reduce menstrual pain and to aid in childbirth. Parts of the plant are also used as an infusion in tonics for goats. Usually, the roots or rhizomes are the parts used for medicinal purposes, but using any part of the fortnight lily for medicinal purposes should never be attempted unless by an experienced healer.

Fortnight lily has been used to relieve menstrual pain.
Fortnight lily has been used to relieve menstrual pain.

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Discussion Comments


What parts are toxic? I'd like to plant these, but have dogs and want to know if it's safe for them.

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