Sedum, Phedimus, Aizopsis - A Stonecrop By Any Other Name?

Sedum is a genus with a long history of decorative, medicinal and edible use, well known to many gardeners, with long popular plants for physic gardens, rockeries, walls, rooves (including modern style green rooves), perennial borders and houseplant collections. It is also one of those huge old genera packed full of hundreds of not always very closely related species. As studies have continued over time, including genetic studies in recent years, many plants have been separated out into smaller genera, including some important in gardens such as Hylotelephium ( often late flowering, herbaceous plants, such as Autumn Joy), Phedimus (typically partially deciduous, low-growing ground covers, such as the spurium types, with serious flower power).

These changes are not universally known or accepted, so you will still see the plants often labelled as Sedum. Now here is where our subject for today gets a bit more controversial: Phedimus. As mentioned, this genus is the home of a number of low-growing species popular as rock garden or ground cover plants, but exactly which species are included is debated. Some limit the genus to those with pink or white flowers (and other technical distinctions, including genetic details) such as P. spurius, from the Caucasus and surrounding areas, others include the species from Asia and Russia's Far East with yellow flowers, such as kamtschatica, aizoon etc. These latter species are separated by some into yet another genus: Aizopsis. Perhaps time and further studies will make the correct classification clear, or this could be one of those matters of opinion-- just how much difference is required to separate related plants into distinct groups? Clearly I don't have the knowledge to make any such determination, nor even really have an opinion on it! Here's one discussion, this page expresses the opinion that the physical characters are not sufficient to separate Aizopsis from Phedimus; (I did see another article which suggested that there was  sufficient genetic distinction to maintain separation, but I can't find that article now, if I do I will add it here! along with any other details that may come up in discussion):   http://flora.huh.harvard.edu/china/novon/Ohbaetal110-4.htm  ..

However, it seems that some botanists working in the region (Russia's Far East) where the plant we are going to look at today is from, use the separation to Aizopsis for many of the species from that region, so that's what I'll go with for now.

Sedum littorale / Phedimus littorale / Aizopsis litoralis /Russian Coastal Stonecrop

This plant came to me as seed from plants originating at the Denver Botanic Garden, and their seed came from a botanist /seed collector who worked in that same far part  of Russia, Doctor Alexandra Bertukenko. She labelled it as Sedum littorale. Now let the taxonomic fun begin!

So, we won't worry about the Sedum part, accepting that has been changed (or not). First, we have to be careful not to confuse with Sedum 'litoreum' a small European species (probably a true Sedum). With that out of the way, we will be looking at Phedimus or Aizopsis, take your pick, from Russia's east coast. This is the home of Sedum / Phedimus / Aizopsis aizoon, and its gaggle of sub/species. This may be where it gets trickiest, since the dozen-give-or-take species/subspecies are separated by rather small details in some cases, and tend to be highly variable, so those distinguishing details may overlap or simply not be there. The following page describes the various sub/species related to aizoon (if you don't read Russian, as I don't, you'll need to opt for translate, as Google offers, I presume other browsers do as well; the 'Eng' link in upper right seems to just take you to an English homepage, not sure you can access species info that way..):

http://botsad.ru/menu/mir-rastenii/atlas-crassul/com-descr/aizopsis/

I may need to spend more time reading the species descriptions to get a really good grasp on the separation between littorale and aizoon, and since both are variable, it is tough-- also note the variation in leaves on immature vs flowering plants in the photos I'm attaching here. There is one photo on that site under Aizopsis aizoon subspecies aizoon which looks more like my plant than any other they show, so that is a good possibility, but with the variability, and giving some credit to the original seed collector, I'll stick with littorale / litorale as a species for the time being, with this whole discussion as caveat!

Immature leaves; Sedum littorale / Phedimus littorale / Aizopsis litoralis /Russian Coastal Stonecrop

Immature leaves; Sedum littorale / Phedimus littorale / Aizopsis litoralis /Russian Coastal Stonecrop

 Thinking as a seed collector, several more thoughts come to mind. First, seed has to be collected when ripe, at which time foliage may be reduced or non-existent (I'll see what my plants do in the weeks to come as seed ripens)- making identification by leaf characters difficult, and the collector may or may not have been to the same place when plants were growing and flowering. Second, species could be delineated by known ranges, so an identification could have been made by the exact location where the seed was collected from- the accuracy then depends on how well known the range of each sub/species is, and whether those evaluations were accurate. A lot of possibilities, none of which I can speak to, so again, I will stick with the original species given (this is also a bit complicated, since the name ending will change to reflect the Latin gender of the genus name, so, Sedum or Phedimus littorale, but Aizopsis littoralis, but there are also various spellings floating around, with different numbers of 't's; original published spelling holds, but I don't know which that is!), genus name changed to reflect regional usage, so Aizopsis litoralis (one t, as the Russian authors used, I’m beginning to feel one t may be correct, though two seems common in horticulture) until someone wiser can take a look and tell me why it isn't.

Developing seed; Sedum littorale / Phedimus littorale / Aizopsis litoralis /Russian Coastal Stonecrop

By any name, it seems like a very good garden plant-- the seasonal foliage (dies back in fall) is a very attractive bright, goldy green, possibly especially on young plants/ pre-flowering stems providing a lovely contrast/complement to darker or bluer greens. Flowering stems are 30cm tall, give or take (no doubt somewhat dependent on site), and it will presumably form nice clumps given a little time. Flat-topped clusters of bright yellow flowers last for a while, and the green-gold of the developing seed capsules extends the effect. Not to count my seeds before they hatch, because you never know!- an animal could eat the ripening seed heads, an early harsh frost could kill them, they could ripen suddenly when I’m not looking and all fall to the ground, etc.. But if all goes well, I will have seed available!

Sedum littorale / Phedimus littorale / Aizopsis litoralis /Russian Coastal Stonecrop

Sedum littorale / Phedimus littorale / Aizopsis litoralis /Russian Coastal Stonecrop

Sedum littorale / Phedimus littorale / Aizopsis litoralis /Russian Coastal Stonecrop