A meeting place for rose breeders.
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I have been enjoying my second season of open pollinated seedlings, trying to get the hang of things before I attempt a cross. There are thirty-six new roses so far, very exciting. The kind advice of all of you has been very helpful. Something puzzles me. Two of the seedlings appear to have large healthy cotyledons but do not seem to be interested in carrying forward with the program. They do not seem to have an apical growth point. In your experience, do you think they have a chance, or is this some kind of lethal variation? Do seedlings like this ever develop growth buds from the leaf (well, cotyledon) axil, or are these seedlings going to just hang out idly until I run out of patience or summer or both?
If they don't have an apical growth point, they're likely never to grow. Early in my hybridizing career, I had several such, and only one of them survived. It developed a thickening between the cotyledons and eventually forced out new growth. Unfortunately, the new growth wasn't worth waiting for. A very poor flower on a poor plant.
I used to have more of that than now. I germinate the seed in baggies and transplant them out as seedlings with cotyledons just opening typically. If I don't use plastic baggies or plastic domes over the trays at first it seems like the humidity drop on a sensitive seedling can dry out the growing point and lead to this. When I elevate the humidty for a little bit until I see a couple leaves starting that seems to help get more of them through that sensitive stage and then I transition the humidity down not too long after seeing some leaves forming. I like the taller plastic domes with vents that can be opened to help transition the humidity down gently. The domes usually stay over the trays for a week with the vents starting to be opened after a few days or so.