Spines or sausages? Two very different Moroccan species in the alphabetically challenged Zygophyllum

Apart from being close to last in any alphabetical list of plants, Zygophyllum zilloides is a species you need to travel to Morocco, or thereabouts, to see in the wild. It's described as a western Saharan endemic, which means the drier parts of Morocco (including what has been separated out until recently as 'Western Sahara'), Algeria and Mauritania. 

The genus Zygophyllum (in the family Zygophyllaceae), with more than 100 species, is far more widespread: from the broader Mediterranean region south into much of Africa, east through to northern China and the western side of the Americas. Mostly growing in arid or drier habitats, the species of Zygophyllum often - but not always - have paired 'leaflets' (zygo = double, phyllum = leaf).

Zygophyllum zilloides, which at times has been classified as Fagonia zilloides, has 'trifoliate' leaves - leaves divided into three leaflets - at the base of the plant, and unifoliate (undivided) leaves at the top. Although in my photographs the spines (stipules at the base of the leaf that have become thorny) are more obvious than the small, unifoliate leaves. But look hard at the top picture and you'll see the leaves.

There's a second species of Zygophyllum growing alongside Zygophyllum zilloides, which couldn't be more different in vegetative form. Zygophyllum gaetulum has no spines but sausage-like succulent leaves. The flowers are so tiny it's hard to see the generic connection, but at least they are a similar pale blue or purple.

The species name, gaetulum, most likely commemorates the Gaetuli, a group of Imazighena (Berbers) living on the western edge of the Sahara during Roman times. This is where it grows today, although it does extend further west to the Canary Islands. Nearly all parts of (thankfully non-spiny) Zygophyllum gaetulum are used in traditional medicine.   

More confusingly for the casual observer, there is a third species of a genus starting with 'z' that looks a bit like our first species, Zygophyllum zilloides. Spiny and with purplish flowers.

If you look closer, Zilla spinosa has different kinds of 'spines' (technically 'thorns', terminating branches rather than flanking the leaves), and an entirely different flower. Those who know the cabbage family will immediately recognise the four-petalled flower as belonging to the Brassicaceae. 

This family is very well represented in Morocco, particularly by yellow-flowered rapes (my general term of the various cabbage family annuals with yellow flowers) but also quite few blue or purple-flowered species.

Zilla spinosa extends right across the top of Africa, through to the Middle East (where it is apparently rare). It's the only member of the genus Zilla, a name coined from a local Arabic name for this plant. At a distance, or driving past in a bus, it looks not unlike Zygophyllum zilloides. But of course, nothing like Zygophyllum gaetulum.