The miserably hot weather we've been having is not "a favorite" with my Petrocosmeas. While they much prefer the cooler temperatures of autumn and winter, the humidity that comes along with the warm temperatures does provide some comfort. As the days get hotter, I lower the number of hours that my lights are on and increase the air movement in the basement growing area. The mature plants seem to just stand still, in suspended animation, while the little seedlings actually chug along, growing at quite a rapid pace.
A few species are in bloom....P. barbata, P. begoniifolia, and even P. nervosa and P. sp. 'vittatae' are blooming. The hybrids, P. 'Asa Blue' and 'Short'nin' Bread' are also in flower now. To test my theory that successful seed set only occurs in cold temperatures, I tried to self all of the above and got nothing. I tried crossing several of them also...and got one enlarging seedpod on nervosa, for a month, then it died. They just seemed to laugh at me and my folly of asking them to do something that I was pretty sure they were not about to do....and they didn't! I have tested pollination in warmer temperatures for two summers now without success. Last year I did get three mature seedpods on P. begoniifolia, but when I opened the dried seedpods, there was not a single seed to be found. I even examined them under a microscope...no seeds. In winter, with cold temperatures, I have much greater success with seed formation.
I mentioned the hybrid seedlings. This summer I am watching a number of exciting new crosses coming along. My favorite, so far, this year, is a cross between P. forrestii and P. minor smooth leaf form. This is only the third hybrid that I have been able to produce from P. minor. The plants are making lovely deep green rosettes, similar in size and appearance to P. forrestii, but with a deep green glossiness to the leaves that is definitely P. minor!!! One seedling in particular has leaves that are very glossy.
A trio of seedlings from a cross between P. forrestii and the smooth leaf form of P. minor. The seedling in the lower portion of the photo is much glossier than it's siblings and a bit deeper green in color. From among a tray of a dozen seedlings, this one has stood out from the very early stages for the glossiness of the leaves. Note the slightly different leaf shapes and the differences in the leaf veining. The seedling in the upper right has leaves that are nearly perfectly round, like minor..... while the other two seedlings have a bit more of a point at the tip of the leaf...more like forrestii.