Euphorbia's Morphological Bonanza

It has occurred to me that I have a tendency to rant on about how Rosa has such an impressive amount of diversity. But looking at morphology, most roses are really very similar-- generally all have compound leaves, prickled canes, and five-petalled flowers in a small range of colors.

In a greenhouse the other day, I saw two very distinct plants-- the common poinsettia, and the houseplant known as "crown of thorns." Well, admittedly, there are easily discernible commonalities between them-- but you get the picture. These vastly different plants are in the same genus, Euphorbia.

Yellow-flowered Euphorbia milii

The classically thorny shrub, fierce and exotic looking but quite easy to grow

Red-flowered Euphorbia milii

E. pulcherrima, the wild parent of ornamental poinsettias (photo credit).

The morphological diversity is especially evident once you include the succulent euphorbias.

E. squarrosa (photo credit)

E. globosa (photo credit)

E. frankiana (photo credit)

Some grow as rather large shrubs:

E. cotinifolia (photo credit)

Just mindlessly skimming over these photos, it doesn't look like the plants are at all related, but in fact each is the same genus-- a degree of morphological diversity that roses certainly can't compete with.