Those of us who love to collect Petrocosmea are faced with a mess. Our beautiful Pets are currently saddled with some very "un-beautiful" names. Some are not even labeled with a name at all but a series of letters and numbers such as Petrocosmea species #5 or Petrocosomea 'Chinese #2' or Petrocosmea species 'HT-2'....certainly not the names one expects when one encounters such a beautiful new plant. All of these letters and numbers are now starting to create a number of issues and the number of species in culitivation begins to expand. To make matters even worse, over the past decade, as China was opened to plant collectors, new species have been collected and incorrect names have been attached by the dealers in China. Often, the same plant was sold with two different names attached to the same plant. So, those who were importing them have distributed the plants with the names as attached. As these have become more widely grown, we are beginning to realize that the names as applied are erroneous. Most of the species we currently have in cultivation are most certainly mislabeled or misidentified. The photo of the lovely Pet flower above is a perfect example. This flower was produced on a plant labeled Petrocosmea floribunda. There is NO published Petrocosmea species with that name. So, where did it come from? Then, it gets even worse, a second plant in my collection bloomed with identical blooms..... that plant is labeled Petrocosmea duclouxii! Obviously, one or both names is erroroneous!
One of my missions, as I focus on the genus, is to begin to sort out all of this muddled misidentity for my beloved Pets and the growers who treasure them. These lovely plants deserve to be correctly identified. So, about a year ago, I began sorting through the botanical descriptions for all of the species within the genus Petrocosmea as published in the Flora of China. Immediately, a number of problems arose. The Flora of China was published several years ago, and most of the species we are currently growing have been collected and introduced within the past 8 years or so. So, there are almost certainly some new, or unidentified species in the mix right now. But, it was a place to start. It is slow and tedious work. First, I have to have fresh Pet flowers, so I have to wait for each species to flower. Then, the flowers must be dissected, and each tiny part identified and measured. Even the hairs have to be measured!!! It takes me days to do each species. But, I am learning so much about the similarities and differences in the anatomy of these plants. Fascinating!!
Study the photo at the right. It shows four of my plants, all different species, growing on my lightstand in the basement. These are all young plants newly potted. In this photo, though, are three clones of what may well turn out to be the same species. They are all labeled differently.
The photo shows (clockwise from top left) P. sp. 'G25KC00' (rosettifolia); P. minor, smooth leaf form; P. menglienensis (likely another form of rosettifolia); and P. rosettifolia. Look at how diffferent the two plants at the bottom and the one at the top left are.... and all are likely the same species, but are currently labeled very differently!
This photo at the right is a blooming plant of Petrocosmea species #5. Others are growing the same plant as Petrocosmea minor veined leaf form. I have gotten the same plant from different sources with both names. DNA are showing that it is closely related to minor, but may indeed be a different species. To make matters worse, the description of P. minor in the Flora of China describes something very different from this plant or the other plants we grow as P. minor...all are likely misidentified.
Another issue with the labeling of Pet species pops up when a newly collected plant comes into cultivation. If the plant is clearly different from the other species we have in cultivation, the grower is faced with the dilemma of what to pot on the label as one begins to distribute cuttings among other growers. This is often where the letters and numbers come from. Below are two photos of newly introduced species. The first is a photo of a newly collected Pet that was just introduced into the US last winter. I have the plant in my collection at present. It is indeed different from anything we currently grow, and it most closely resembles plants labeled P. sericea and P. sp. 'HT-2', but it is definately different from those. A lovely plant, with very flaccid, very soft, felt-like silver leaves. An exciting and beautiful new introduction, whatever it turns out to be.
Note the very dense and long silvery hairs on the calyx lobes at the base of each flower....lovely!
The last photo below, shows a plant that I imported from China in 2005. It came labeled P. forrestii, but is clearly not the same as the plant we currently grow as P. forresttii. So, I labeled it P. species 'China 2005'. It makes a lovely, small rosette, and the flowers are a very different blue-purple color with a contrasting white throat. Pedicels often have a purple blush to them. It bears single flowered cymes, and last year, was very reluctant to cross with any other species in my hybridizing attempts. It did finally cross with P. forresttii and I have five seedlings nearing flowering size now. DNA is showing that it is closely related to the other plants that we grow labeled P. rosettifolia....so it may turn out to be another clone of that species. A charming plant, nonetheless.
So the taxonomy within this genus is a mess, to say the least. The genus is badly in need of some work from taxonomists. Currently, I am honored to be participating in some DNA studies being done with a university and this may help to sort out some of the confusion, but will not do a lot to ensure that the names on are labels are properly applied. Until that day comes, I carefully label each plant and each leaf I distribute from each plant with the name on the label when I acquired it. I don't change anything until the proper science is applied. Then, I just relax and enjoy growing my beloved Petrocosmeas!