Colutea arborescens

This is a large shrub or small tree reaching heights of 4-5 m. The branches have a spongy or hollow core, just as the elder does. The young twigs have laminar rib-like expansions. The leaves are deciduous, alternate and compound with 3-7 pairs of leaflets as well as a terminal leaflet (odd-pinnate). These leaflets are 0.8-3 cm long and 0.5-2.5 cm wide, oval, elliptical, or rounded, and are notched at the tip. They are hairless on the upper side and have a fine soft down on the underside. The flowers are very showy; they are borne in hanging clusters of 2-8 units, and are yellow-gold in colour. They also have very fine reddish veins on the banner (the upper petal of the legume flower, which is usually bigger than others). It differs from other species in the same genus because the female part of the flower, the ovary, is either hairless or has a row of hairs. The fruit is very characteristic: when mature, it is a 4-9 cm long, globose legume with an inflated appearance, and is papery in texture.

Flora iberica describes two further species of Colutea, which are very similar and easily confused with this one. Both of these species are never more than 2-3 m high, branching shrubs, although in the contact zones they generate hybrids with intermediate characteristics, making identification even more difficult. For this reason we mention here: Colutea brevialata Lange, characterised by having an ovary which is very hairy across its entire surface; and Colutea hispanica Talavera & Arista, which is defined by having a hairless ovary. However, the botanist Ginés López considers that it would be better treat the latter as a subspecies of C. arborescens.