Euphorbia 'Diamond Frost': what's with the confusing names?

A recent post made me want to dig a bit deeper into the Euphorbia 'Diamond Frost' problem. I suppose more accurately, I wanted a place to house the many links I was generating regarding the history of how Euphorbia 'Diamond Frost' was named and maybe provide some clarity on what name should be used. Hopefully, this will act as a useful resource for anyone who also happens to be confused or annoyed by the problem.

Euphorbia 'Diamond Frost' has an odd history with taxonomy. It is commonly sold incorrectly as E. hypericifolia. 'Diamond Frost' is shown to be most closely related to E. graminea based on phylogentic and morphological evidence (E. graminea belongs to sect. Alectoroctonum while E. hypericifolia belongs to sect. Anisophyllum). One simple way to distinguish the two is to look at the lowest (non-bracteate) leaves. These will be opposite in E. hypericifolia and alternate in E. graminea (sometimes becoming whorled at the base of the inflorescence before becoming opposite when cyathia for the rest of the inflorescence; see pleiochasial and dichasial bracts). Problematically, the company that originally trademarked the name considers 'Diamond Frost' a hybrid, but what of is not specified. My best guess is that the company considers if a hybrid of cultivars rather than species.

Susan Mahr at the University of Wisconsin – Madison indicates that 'Diamond Frost' is a trademarked name that Euphorbia 'Inneuphdia' is commonly sold under. This cultivar was patented in 2005 under the name Euphorbia hypericifolia, though the trademarked name of 'Diamond Frost' is older. Given that it cites no prior cultivars and later cultivars cite Euphorbia 'Inneuphdia', I find it likely that this was the original patent that started the confusion. Many subsequent patents use Euphorbia or Chamaesyce hypericifolia but mention Euphorbia 'Inneuphdia'. One odd patent uses Euphorbia x hybrida (photo), but this is an intercultivar and not an interspecific hybrid as the Euphorbia 'Flame' used as the pollen parent is almost certainly Euphorbia 'Flameleaf' or another similar cultivar of E. graminea. Remarkably, one patent did provide the correct name.

Now, as for why 'Diamond Frost' is considered a "Euphorbia hybrid", I can't say for certain but know two things: 1. the initial patents provided names and 2. intercultivar crosses are close enough to hybrids in this confusing example. As such, I find it likely that the holders of the trademark recognized the taxonomic confusion and just went with Euphorbia hybrid to avoid controversy. It's just a hypothesis, but unless 'Diamond Frost' has changed since Euphorbia 'Inneuphdia' was initially patented, I find it the most likely outcome.

הועלה ב-מרץ 13, 2023 01:22 לפנה"צ על ידי nathantaylor nathantaylor


An interesting study, thanks! I have owned this variously through the years but not paid it much attention, since it's a potted plant bought at a store. I gave my last one to my landlady, who put it in the ground, but I don't think it survived the winter. Maybe the next time I end up with one, I'll look more closely at it.

פורסם על-ידי ashley_bradford לפני 5 חודשים

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