Yellow Oleander
Thevetia peruviana
NEMBA category
English: Yellow Oleander, Lucky Nut, Mexican Oleander, Be-Still Tree, Trumpet Flower
Afrikaans: Geeloleander
Shona: Chinanga, Mukaya
Historical scientific names: Cerbera peruviana, Cerbera thevetia, Thevetia neriifolia
Thevetia peruviana, commonly known as Yellow Oleander or Lucky Nut, is a dense, evergreen shrub or small tree. It is easily recognised by its bright yellow, trumpet-shaped flowers and distinctive, somewhat triangular, green fruits that turn black when mature.
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Origin:
Mexico, West Indies, and parts of Central and South America.
Distinguishing features:
Bright yellow, trumpet-shaped flowers that are twisted in bud.
Narrow, glossy, lance-shaped leaves.
Green, roughly triangular fruits that ripen to black.
Milky, highly toxic sap.
Overall appearance:
This plant is typically a dense, leafy, evergreen shrub or small tree, reaching several metres in height. It has a rounded, bushy habit with upright branches.
Height:
Up to 6 metres, though it can sometimes reach 8 metres.
Width:
It can form a spreading bush, with a width of around 4 metres or more.
Leaves:
The leaves are narrow, lance-shaped (like a spearhead), bright green and glossy on the upper surface, and paler underneath. They are spirally arranged along the stems and can be 8-16 cm long and 0.5-1.4 cm wide.
Flowers:
The flowers are a vibrant yellow (though sometimes orange or white cultivars exist), trumpet or funnel-shaped, and distinctively twisted in the bud. They are borne in clusters of 6-8 flowers. Thevetia peruviana is hermaphroditic, meaning each flower has both male and female parts, so it is not dioecious (having separate male and female plants).
Flowering season:
In South Africa, it can flower for much of the year, especially from late spring through summer, but the main flowering period is generally from October to December.
Fruits:
The fruits are distinctive drupes (fleshy fruits with a hard inner stone), somewhat globular to broadly triangular in outline with a raised ridge across the middle. They are initially bright green, slightly fleshy, and eventually harden and turn black. Each fruit is typically 2.5-5 cm in diameter and contains 1-4 seeds.
Seeds:
The seeds are light grey, lenticular (lens-shaped) to somewhat triangular or kidney-shaped, and woody. They are enclosed within the hard inner stone of the fruit.
Bark:
The bark is light grey and tends to remain smooth even on mature plants. The stems are green when young, turning silver-grey with age.
Thorns:
This plant does not have thorns.
Wood:
The wood is reportedly white and can be used for making tool handles.
Roots:
The plant is shallow-rooted and should be protected from strong winds.
Soil type:
It prefers soft, deep, and very well-drained soil. It can tolerate a variety of soils, including poor soils, but not heavy clay. It is also tolerant of moderately saline soils.
Aspect:
Thrives in full sun but can tolerate light shade. It is well adapted to heat and drought.
Edibility:
All parts of Thevetia peruviana are highly toxic and should not be eaten.
Toxicity:
All parts of the plant are extremely toxic due to the presence of cardiac glycosides (such as thevetin A and B, neriifolin, and oleandrin). Ingestion can be fatal to humans and animals, affecting the heart. Even the milky sap can cause skin irritation.
Uses:
Primarily cultivated as an ornamental plant in gardens and parks due to its attractive flowers and evergreen foliage. It can also be used for hedging. Historically, the seeds have been used to make jewellery, and in some traditional medicine systems, although extreme caution is advised due to its high toxicity. Seed oil has been used in industry (e.g., soap making).
Ecology:
As an invasive species, it competes with and replaces indigenous vegetation, especially in disturbed areas and along watercourses. Its toxicity poses a risk to livestock and potentially wildlife if ingested. While some birds have been observed feeding on the fruits or nectar in its native range, the overall impact on local ecosystems in South Africa is negative.
Distribution and habitat:
In South Africa, Thevetia peruviana is found as an alien invasive primarily in the warmer, higher rainfall regions. It is particularly problematic in Gauteng, KwaZulu-Natal, Mpumalanga, Limpopo, and the Eastern Cape. It invades roadsides, waste areas, disturbed sites, gardens, riparian zones (along watercourses), and open woodlands.
Derivation of name:
The genus name Thevetia honours André Thevet (1502-1592), a French monk and explorer who travelled in Brazil and Guiana.
The species name peruviana refers to Peru, where it was originally thought to originate, though its native range is broader.
Common names like "Yellow Oleander" refer to its resemblance to the common oleander (Nerium oleander) and its yellow flowers. "Lucky Nut" refers to the appearance of its seeds.
Historical aspects:
Thevetia peruviana has been widely cultivated as an ornamental plant in tropical and subtropical regions around the world for many years due to its attractive appearance and ease of cultivation. Its toxic properties have also been known for a long time, leading to its traditional use in poisons and, with great caution, in some medicinal applications.
NEMBA status:
Category 1b in Eastern Cape, KwaZulu-Natal, Limpopo, and Mpumalanga. Category 3 in Free State, Gauteng, North-West, Northern Cape, and Western Cape. (Note: Plants in riparian areas are always Category 1b).
Interesting facts:
Fancy a "lucky nut"? Don't be fooled by the name – these attractive seeds are packed with powerful toxins! Best admired from afar.
This plant is a master of disguise, sometimes mistaken for its cousin, the common oleander, but look for its distinctive twisted flower buds and more triangular fruits to tell them apart.
Despite its pretty flowers, Thevetia peruviana is a bit of a bully in the plant world, pushing out local plants where it invades.
Imagine a plant that can thrive in tough conditions, even dry ones – this "yellow oleander" is quite resilient, which is part of why it's such a successful invader!
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