Externmed, where the pots in baggies or under propagation domes? How close to the lights were the seeds? Did you keep the potting mix moist in the pot under lights? There are a lot of variables. I get my best germination of Ericaceous plants by surface sowing, and with the top of the potting mix about six inches below my 40-watt cool white lamps, at a room temp of about 55F (the temp under the lights is around 60F). The pots are fully enclosed in a sealed freezer bag. When they germinate under the lights, they don't have a chance to stretch and weaken.
SW Washington state, 600 ft. altitude
Hi Gene,The two identical pots with the same surface sown seeds germinated better in the dark at 60F, than in the light at possibly 80F in a baggie. I was just guessing that 80F and bright light was too much for this Rhodendron; but I was surprised with near total germination in near darkness. They warm seeds germinated at least 60% when I moved them to the dark roomI wouldn't have normally used the bright light, but I had had a recent failure with the standard fluorescents--so it just went under there.I have a room that I keep at 42F for the winter; if I have the time and ambition, I'll hopefully start a lot of seed in there next fall.Thanks for your comments and suggestions,Charles S
NE Massachusetts (New England) USA zone 6 (5B to 6B)
gardens visited, photographs: www.flickr.com/photos/wildmeadow
I haven't tried a 42F room, but I'll bet that fluorescents in a 42F room will be magical for germinating alpines, bulbs, etc. But growth will be slow at that temp. I suspect that would be a perfect setup for the European alpine Gentians.
This was one of my firstsuccesses with rhodo seed: R suchuenense, about 20 years ago. I used soil from the spruce woodland nearby and didn't cover the seeds. Kept the pot in a semi cold greenhouse during the winter. Now the shrub is 3m tall and 4m wide.
Rogaland, Norway - with cool, often rainy summers (29C max) and mild, often rainy winters (180 cm/year)!