I've grown 'Purpurea' in my garden and 'Blackbird' in containers. They are very similar, although 'Blackbird' is indeed somewhat darker.

'Purpurea' can sometimes be propagated by seed, so there are good and poor forms out there.

My expectation is that 'Blackbird' is slightly less hardy though. It is often described as a sport of 'Redwing', which is a cultivar of E. characias.

I've grown both and have seen them in a grower's setting as well. They ARE quite similar in appearance - in full sun, side by side, it's a bit difficult to tell them apart until flowering. 'Blackbird's bracts are not as intensely chartreuse or limey green as 'Purpurea'. They have more of a reddish tone to them and can be mottled with the same deep purple tones of the regular foliage, which in full sun can get very dark - nearly black. I've never seen this with 'Purpurea', which generally has very bright lime green/chartreuse bracts. 'Purpurea', being a straight cultivar of C. amygdaloides (wood spurge), is more shade tolerant as well. And a zone or two hardier.

Not to be too nitpicky, 'Redwing' is a hybrid, being a cross of E. amygdaloides and x martinii. And obviously, E. x martinii is itself a hybrid, a naturally occurring cross of E. amygdaloides and characias. So there's a great deal of amygdaloides in 'Blackbird's parentage but enough characias to make it somewhat less hardy than 'Purpurea'.

'Purpurea' will self-sow under good conditions: 'Blackbird' is sterile and will not.

This is great information. Thanks.

How does their winter appearance compare?

gardengal, you're right on the history/parentage -- obviously 'Blackbird' has some E. amygdaloides "blood" in it. I'm not sure why the Planthaven site lists 'Redwing' as only a cultivar of E. characias.

In any case, the E. characias influence will likely decrease the hardiness somewhat of 'Blackbird' vs. 'Purpurea'.

Garry, in both cases, cooler temps influence the dark foliage. 'Blackbird' will simply be darker/blacker in the winter. IMO, at least here, despite their semi-evergreen characteristic, they can still look pretty "beat up" by late winter.

I had one of my 'Blackbird's fail this winter. The thing looks like toast! Since my area is a pretty much ideal climate for all manner of euphorbias (our local Skagit Gardens is a hybridizer and licenseholder for many of these newer introductions), I am at a loss to know why it didn't survive the winter. All my other euphorbias look great, are blooming or setting buds and beginning to push new growth but the two remaining Blackbirds are looking somewhat less than wonderful. Maybe they just need more time to establish, as they were new last season.

FWIW, in my climate - never hot - the best foliage color on those euphorbs that have reddish/purplish coloration is on the new growth (early spring) and just as fall is beginning.

Here are some pics of my Euphorbia amygdaloides 'Purpurea' that I recently planted. I planted it throughout my border to provide some additional interest in the winter. I'm looking forward to it filling in. I love this plant.

{{gwi:198642}}

{{gwi:198643}}

And here is Euphorbia x martinii 'Tiny Tim' that I also recently aquired. I have the standard form and was happy to see it offered in a "minature" size as well. This one is supposed to to be a repeat bloomer all season long according to a number of sources.

{{gwi:198644}}