I'm not sure if the problem was having too much time on my hands or having too many Petrocosmeas on hand, but the thought occured to me, and I just had to do it! Actually, I'm certain it wasn't the former, because there never seems to be enough time in the day.... Nonetheless, I'm now well on my way with an experiment in growing Petrocosmea outdoors in southwestern Pennsylvania. Pittsburgh is in USDA zone 6, and my outdoor growing space is pretty cool and shady. Our summer temperatures here are relatively mild, with lots of rain. As I thought about it, I realized that our climate here is pretty close to what I've read about the natural environment where many Petrocosmea species grow in China, so I figured...."why not?"
So, here's what I've done. First, I selected the plants I wanted to use a couple of weeks ago, and let them dry out to the point of being limp....I did this in order to avoid breaking leaves off of brittle, turgid plants. Then, I took an old terracotta "strawberry jar", (I've had this thing forever!!!) and filled it with a loose, but fertile soil mix that included lots of humus and a little composted manure. I selected a collection of species that offered variety. And, having groomed more than my fair share of dirty Pet leaves, I decided to fill the jar and start to pot from the top, in order to avoid soil from above falling onto the leaves of the plants below. This is backward from the way I would normally pot up a strawberry jar, but for the Pets, it worked flawlessly. And, since Petrocosmeas are "rock plants" I had to include a large rock on the top for some ornamentation and interest. The Pet species I used were : minor veined leaf form, rosettifolia forms #2, and #3, barbata, forrestii, begoniifolia, nervosa, and kerrii. I mulched any exposed soil with small gravel and watered them in with a vitamin root stimulant diluted in water. They will remain in total shade and I sited them so that they will get good air movement. Luckily the spot is also along the path I take into and out of the house each day as I go to work, so I can see my beloved Pets at the start and end of my dayI!
I'll let you know how the experiment progresses!