Saturday, November 28, 2009

The Rosettifolia group - Part I

When I first began to assemble a collection of every known Petrocosmea species in cultivation, about five years ago, I noticed that I had two different plant labeled as Petrocosmea rosettifolia. They looked different in several ways. Then as time went on, I began to notice that some of the P. rosettifolias entered in shows were different from the two plants I had. I decided to get leaves of all the various forms I could find and conduct an experiment. I put leaves of all four forms that I had collected down to root on the same day. I treated them identically in every way. When they had formed plantlets, I divided and potted up the plantlets on the same day, using the same soil, pots, fertilizer, etc. I grew them on the same shelf of my lightstand. The culture was identical in every way, at least as much as I could make it so.

As these four individuals matured, I could easily see the differences. I decided to label them P. rosettifolia #1, #2, #3, and #4 so that I could keep them seperately identified and kept records of each form.

Were they different species, or just different clones of the same species, perhaps from different collections or populations in nature? Those questions are still being answered, but with time, based on morphology and now some new DNA analysis, I am convinced that they are indeed four unique individuals within the same species. I do, however, have real doubts that they are indeed the true P. rosettifolia, but I am leaving them labeled as such for the timebeing.

I feel that it is important to both Petrocosmea admirers as well as AV and gesneriad judges and exhibitors to know that there are four different clones of this species in cultivation and they grow and perform differently. Furthermore, I believe that the plants now being grown as P. menglianensis and P. sp. 'China 2005' may also be two additional clones of this same species, based on the DNA analysis which is being done as well as morphological characteristics of these plants. Two others, P. sp. 'Chinese #2' and P. sp. 'Yumebutai' is also very closely related to this group and may be two additional forms of the same species. I refer to all of these collectively as the "Rosettifolia group".

I decided to review the four forms that I have identified here.

The first is of course, P. rosettifolia #1. My plant was labeled as coming from the collection of the late Maryjane Evans, and it is believed to have been a plant collected in China around 1998-2000. This form is the smallest of the four clones in plant size. It has never reached the edges of the 5 inch pan pot in which I have grown it for the past three years. It's rosette is rather tight, and leaves are the smallest of the four clones, and are nearly plain dark green, with only a slight gloss to them. The yellow center vein coloration so prominent in the leaves of some other forms of this species, is very faint in the leaves of this form. Leaf margins are entire, or smooth, showing no teeth as some forms do. The flowers of this form are produced on single-flowered peduncles, with two bracts, which tend to be the shortest peduncles of the four forms and the most often curve gracefully at the tip, causing the open flowers to "nod" downward slightly. The flower form shows two fused upper petals forming an hooded lip, which is green in color and only half the length of the lower three petals, which are a pinkish lavender in color. It forms a rather charming little rosette when in flower. It is a favorite of mine for it's simple charm.

A blooming P. rosettifolia #1, showing it's charming simplistic habit.

The flowers of P. rosettifolia #1 are the closest to pink of any Petrocosmea species in my collection. The subtle coloration of pink, lavender, white, creamy yellow and green is lovely.
The next is P. rosettifolia #2. The origin of this plant is unclear, but it was believed to have been brought into cultivation via a purchase from Chen Yi Nursery, in China. My plant was purchased from a commercial vendor here in the USA four years ago. This plant is very similar to #1, but grows a bit larger in all it's parts. Leaves are larger and the rosette just reaches 5 inches in diameter. Leaves are a bit glossier than #1, and the rosette is slightly more open in form. Flowers are nearly twice the size of the flowers on P. rosettifolia #1. The peduncles are single flowered, with two bracts and are very straight, with little or no curvature at the apex once the flower buds open. Flowers are presented facing outward and upward. Coloration on these is more lavendar, with little to no pink coloration. Flower form is identical to form #1 and very similar to P. menglianensis. This form appears identical in all respects to the plants now being grown here in the USA as P. sp. 'Chinese #2'.

A blooming plant of P. rosettifolia #2. A bit larger than form #1, again without the yellow central veining that some forms show. Leaf margins are entire, showing no teeth. This form bear two bracts on each peduncle.

The flowers of P. rosettifolia #2 are twice the size of those on P. rosettifolia #1.

This photo shows P. rosettifolia #1 on the lower left, with P. rosettifolia #3 above. You can just see the leaves of P. menglianensis to the right of P. rosettifolia #1.. Note the difference in the rosettes of each species, along wit the leaf margins and the yellow veination of the leaves on #3. I believe P. menglianensis to be the same species as the rosettifolias. It's leaves are quite large, and show the yellow veination that form #3 does, but have a smooth or entire margin, whereas form #3 had a serrate leaf margin and a narrower, more pointed leaf shape.

By growing the various forms side by side, it becomes easy to note the similarities and differences in the plants. The photo above shows how they were grown on the lightstand. Note the white acrylic blanket matting in the bottom of the nursery tray, which is used to maintain higher humidity around the plants.

A couple of additional points I'd like to make about the various forms of P. rosettifolia. Forms #1 and #2 have smaller habits, which judges should take into account when judging these species. The leaves are less ornate, having plain green coloration. The leaf margins are smooth, or entire on the forms #1 and #2 and are serrated, with teeth on forms #3 and #4 which will be discussed in the next post. The peduncles of forms #1 and #2 consistently have two bracts, while those of forms #3 and #4 consistently have three bracts per peduncle. Last, I would like to state again, that these plants are labeled P. rosettifolia, but I believe they are NOT the true P. rosettifolia as described in the Flora of China. I believe they may indeed be an undescribed species. DNA evidence being finalized now, shows that the four forms of P. rosettifolia that I am describing here are very closely related, so closely that they are likely all the same species.