Acacia

The genus Acacia comprises about 1200 species of trees and shrubs, many are spiny, although others are unarmed. The leaves always have an entire margin and can be deciduous, compound and pinnate (twice or more). Some species are persistent with phyllodes, laminar expansions that function like leaves, but which have not developed as such and therefore lack axillary buds. The flowers are yellow and aromatic. They are borne in globose or elongated groups which often form clusters, so the blossom can be very attractive and spectacular. The fruit is a legume, usually containing several seeds.

On the Iberian Peninsula there are up to 11 naturalised species of very similar-looking trees that are commonly referred to as mimosas.

1. Acacia baileyana F. Muell. Mimosa. Evergreen tree or shrub with no thorns; pinnate leaves, with 2-6 pairs of leaflets and no phyllodes; very aromatic yellow flowers in glomerules grouped into clusters.

2. Acacia dealbata Link. Mimosa. Evergreen tree with no thorns; bipinnate leaves, with 10-26 pairs of leaflets and no phyllodes; very aromatic yellow flowers in glomerules, grouped into clusters. Included in the Atlas of invasive alien plants of Spain.

3. Acacia decurrens (J.C. Wendl.) Willd. Acacia bark, early black wattle, green wattle, Sydney wattle, wattle bark, tan wattle, golden teak, Brazilian teak; Aromo, mimosa. Evergreen tree with no thorns; bipinnate leaves, with 8-15 pairs of leaflets and no phyllodes; bright yellow flowers in glomerules, grouped into clusters.

4. Acacia farnesiana (L.) Willd. Needle bush, Ellington's curse; Aromo, mimosa. Very thorny shrub or small tree, with spines up to 2 cm long; deciduous bipinnate leaves, with 2-8 pairs of leaflets and no phyllodes; very aromatic yellow-golden flowers in clusters.

5. Acacia karroo Hayne. Sweet thorn, Karoo thorn, Cape gum, Cockspur thorn; aromo de Sudáfrica, acacia karóo. Thorny shrub or tree, with spines up to 10 cm long; deciduous bipinnate leaves, with (1)2-7(13) pairs of leaflets and no phyllodes; yellow-golden flowers in globular glomerules.

6. Acacia longifolia (Andrews) Willd. Long-leaved wattle, golden wattle, coast wattle, sallow wattle, Sydney golden wattle; acacia, acacia blanca. Evergreen tree or shrub, with no thorns; all the leaves are reduced to 6-20 cm long phyllodes; flowers in cylindrical glomerules. Included in the Atlas of invasive alien plants of Spain.

7. Acacia mearnsii De Wild. Black wattle; mimosa, mimosa negra. Evergreen tree with no thorns; bipinnate leaves, with 8-25 pairs of leaflets and no phyllodes; yellow flowers in glomerules, grouped into clusters.

8. Acacia melanoxylon R. Br. Australian blackwood, Sally wattle, lightwood, hickory, mudgerabah, Tasmanian blackwood, black wattle; acacia, acacia negra. Evergreen tree with no thorns; leaves of young plants are bipinnate, in adult specimens reduced to 6-14 cm long phyllodes; yellow flowers in globose glomerules. Included in the Atlas of invasive alien plants of Spain.

9. Acacia pycnantha Benth. Golden wattle; mimosa. Evergreen tree or shrub with no thorns; leaves 6-20 cm long, all reduced to phyllodes; yellow-golden flowers in glomerules grouped into clusters.

10. Acacia retinodes Schltdl. Retinodes water wattle, swamp wattle, wirilda, ever-blooming wattle, silver wattle; acacia blanca. Evergreen tree or shrub with no thorns; leaves 3-20 cm long, all reduced to phyllodes; yellow flowers in glomerules grouped into clusters.

11. Acacia saligna (Labill.) H.L. Wendl. Coojong, golden wreath wattle, orange wattle, blue-leafed wattle, Western Australian golden wattle, Port Jackson willow; acacia de hoja azul. Evergreen tree or shrub with no thorns; leaves 8-20 cm long, all reduced to phyllodes; yellow or orangey flowers in glomerules grouped into clusters. Included in the Atlas of invasive alien plants of Spain.