Certainly my favorite in the "Rosettifolia Group" is this species, P. sp. 'China 2005' The flowers are a lovely purple and the plant is literally loaded with buds and flowers. Easily the most floriferous species of the grouping.
A photo of one of my three plants of P. sp. 'China 2005' just coming into flower this week. This plant is three years old. Maturity of at least three years on Petrocosmea plants is proving to be a factor in heavy bloomset. Most Petrocosmea seen in shows, I suspect, are less mature at one to two years, and therefore often don't show a heavy display of bloom.Here is yet another plant which I feel based on both morphology and DNA studies,belongs in the the "Rosettifolia Group". It is either another clone of the plants currently labeled P. rosettifolia in the USA, or at the very least, is a close relative or variety of that species. This plant was imported, by myself, as a wild collected plant in the year 2005. In the catalog from which it was purchased, it was labeled P. forrestii... it clearly is not. It shows no similarities with that species. In morphology, it is most similar to the P. rosettifolias, however neither it, nor any of the other plants currently labeled P. rosettifolia match the published description of P. rosettifolia in the Flora of China. AAahh, yes, yet another identification issue with our beloved genus Petrocosmea!
Recent DNA work is showing that P. sp. 'China 2005' is very closely related to the Rosettifolia grouping of species. It may turn out to be another clone of that species, (whatever it is) or at least a variety of that species. The only morphological difference that I can see is that the corolla color is deep purple, whereas the corollas on the other individuals in this grouping are white to very pale lavendar at best. The flower structure and plant structure and habit all match, however. This bloom cycle, I hope to try crossing it with my P. rosettifolias to see if they cross with each other.
The leaves of this species are plain, deep green and have a rough texture due to the short hairs. Leaf size, shape and plant size and habit all very closely resemble P. rosettifolia #1 and #2. This form is a very heavy bloomer...producing waves of buds over a period of four to five months in my conditions. Flowers are a lovely deep purple with a striking, purest white throat, which is slightly green at the very base of the tube. Petals most always number five...two up and three down, with the upper petals fused and bending forward to form a green "hood" as all of the other P. rosettifolias do. The flower morphology places the plant in Section - Anisochilus of the genus.
I have distributed leaves to a number of Petrocosmea growers over the past four years, and hope that this species will get into wider cultivation. It is a lovely plant in flower, and deserves a safe place in cultivation. Since it's place of collection is not known, and with the rate of destruction of habitat in China, it is a constant fear that this species and other plant species will be or may already be lost to nature forever. Keeping them alive in our collections and our hearts and hands is one way to ensure that they continue to amaze and delight us and future generations for years to come.
In bloom, this is one of my most favorite of all Petrocosmeas! Really! The masses of violet purple flowers on wiry peduncles are a lovely, charming gift each December, and they often last four or five months in my basement growing area. No other species has flowers this small and of this shape and color. Most others with this size and shape of flower have pale lavendar or white flowers, so this species is unique in that regard. Out of flower, however, this species is admittedly a bit lackluster in appearance. 
Compare the form of this species with that of P. rosettifolia #1 and #2, and perhaps even P. menglianensis in my previous posts. It is hard to tell them apart. The key difference, for me, is that the leaves of this species feel "rough" when compared to those of the other species. Very "sandpaper-like" in texture. 
One of the features of this species, which in my opinion detracts, is it's pesky tendency to form offsets when mature. Maturity brings a very heavy budset and flower count, but with the nuisance of offsets which spoil the flat, symmetrical shape of the plant's rosette, which it has to perfection as a younger plant. As can be seen here, even the offset if putting up a few buds.... This little species just loves to bloom!So, to recap this thread of posts, so far, we have P. menglianensis, P. rosettifolia #1, P. rosettifolia #2, P. rosettifolia #3, and now P. sp. 'China 2005'. There are still others to come! While these plants as labeled, are called by various names at present, they may all turn out to be mislabeled. That is why I refrained from applying a species name to the species covered in today's post, and chose instead to just call it P. sp. 'China 2005'. Such labeling will indicate it's genus, place of origin and the year it was collected.
