Horsetail Tree

Scientific Name : Casuarina equisetifolia L.
Common Name : Horsetail Tree
Chinese Name : 木麻黃, 牛尾松, 馬尾樹
Family : CASUARINACEAE
Local distribution status : Exotic species

Anecdotes on plants

Origins Native to Australia and the Pacific islands.
Applications The Horsetail Tree has a diversified usage. It grows rapidly, does not have strict requirement on soil quality, and has a broad and deep root system stabilizing the soil. Being resistant to drought, salt, wind and sand, it can stop desertification. Hence it is a common species for windbreaks in coastal and desert areas.
Its timber can be further processed into boats and construction materials. It is also a quality source of charcoal.
Young branchlets can be fed to livestock.
As recorded in Flora Reipublicae Popularis Sinicae, its bark contains tannin, which can be applied as an astringent. Meanwhile, leaves and branchlets can be used for curing chronic bronchitis.
Meanings of names Pendulous branchlets look like the tails of a cow or a horse, while it also grows a cone-like infructescence, therefore giving it the Chinese name “Oxtail Pine (牛尾松)” and English name “Horsetail Tree”.
Though the appearance of the species is similar to a pine, it is actually a flowering plant, which you may observe carefully during its flowering period.

Traits for identification

Growing habit Evergreen tree. Crown narrowly conical.
Height To 35 m.
Stems Trunk straight and robust, to 70 cm in Diameter at Breast Height (DBH). Bark of old trees dark brown, rough, with irregular longitudinal fissures, adaxially reddish brown. Ultimate branchlets greyish green, slender and soft, pendulous, with 7 to 8 furrows; contains chlorophyll, replacing the function of the reduced leaves to conduct photosynthesis.
Leaves Reduced to scale-like leaves, often whorled in 7, triangular to lanceolate, appressed to branchlets or erected. Only visible when getting close.
Flowers Female inflorescence reddish brown, always grows into a mess of hairy knots.
Male inflorescence light brown, like spike of grains.
Fruits Cone-like infructescence ellipsoid. Bracteoles lignified, apex slightly obtuse or acute, wart-like. Samaras, dispersed by wind.
Flowering period April to May in Hong Kong.
Fruiting period July to October in Hong Kong.
Remarks

Scientific name above is based on Hong Kong Herbarium website : https://www.herbarium.gov.hk/en/hk-plant-database/plant-detail/index.html?pType=species&oID=8377

Scientific names from other databases
Flora of China : Casuarina equisetifolia Linnaeus
Plants of the World Online : Casuarina equisetifolia L.

Reference