Thorntrees (Plants of Don Edwards Wildlife Refuge)

Thorntrees

Acacia

Summary ³

Acacia (/əˈkeɪʃə/ or /əˈkeɪsiə/), also known as a thorntree, whistling thorn or wattle, is a genus of shrubs and trees belonging to the subfamily Mimosoideae of the family Fabaceae, described by the Swedish botanist Carl Linnaeus in 1773 based on the African species Acacia nilotica. Many non-Australian species tend to be thorny, whereas the majority of Australian acacias are not. All species are pod-bearing, with sap and leaves often bearing large amounts of tannins and condensed...

Description ⁴

The leaves of acacias are compound pinnate in general. In some species, however, more especially in the Australian and Pacific islands species, the leaflets are suppressed, and the leaf-stalks (petioles) become vertically flattened in order to serve the purpose of leaves. These are known as "phyllodes". The vertical orientation of the phyllodes protects them from intense sunlight since with their edges towards the sky and earth they do not intercept light as fully as horizontally placed leaves. A few species (such as Acacia glaucoptera) lack leaves or phyllodes altogether but instead possess cladodes, modified leaf-like photosynthetic stems functioning as leaves.

The small flowers have five very small petals, almost hidden by the long stamens, and are arranged in dense, globular or cylindrical clusters; they are yellow or cream-colored in most species, whitish in some, or even purple (Acacia purpureopetala) or red (Acacia leprosa (Scarlet Blaze)). Acacia flowers can be distinguished from those of a large related genus, Albizia, by their stamens, which are not joined at the base. Also, unlike individual Mimosa flowers, those of Acacia have more than ten stamens.

The plants often bear spines, especially those species growing in arid regions. These sometimes represent branches that have become short, hard, and pungent, though they sometimes represent leaf-stipules. Acacia armata is the kangaroo-thorn of Australia, and Vachellia erioloba (syn. Acacia eriolobata) is the camelthorn of Africa.

Acacia seeds can be difficult to germinate. Research has found that immersing the seeds in various temperatures (usually around 80°C (176°F)) and manual seed coat chipping can improve growth to around 80%.

Perfume ⁴

Vachellia farnesiana (syn. Acacia farnesiana) is used in the perfume industry due to its strong fragrance. The use of acacia as a fragrance dates back centuries.