I checked the nearly 50 bags of seeds, most of them from the Maple Society seeds exchange, I have in the fridge, and two batches are starting to germinate: I spotted a long white root in the bag of Acer morifolium, and several in the bag of Acer rubescens. Acer morifolium: The period of dormancy varies from one species to another, these ones don't seem to need a lot of time since I put them in the mix of sand and peat on January 7th. Others, like A. shirasawanum are required a period of 2 months warm stratification, then 3 months of cold stratification, according to the "literature" one can find. Maybe what I experimentted helped : twice, I took the whole lot out of the fridge and left them overnight in the kitchen (18-20° C), and I even put them all outside for about 5 days when it snowed (-8°,-2° at night, -2°, +5° in the afternoon, but the layer of snow probably kept them a bit warmer). The idea was to have periods of warmer, then colder temperatures like they might have in their natural environment rather than keeping them all the time at the same temperature. I thought perhaps it could help for species for which it is advised to have two periods of stratification - although three Acer shirasawanum 'Aureum' from about ten I kept in the fridge germinated last year. They were from a tree in a pot I have in my garden. It just shows that when you don't have a lab, you have to rely on your green thumbs. Or more probably, luck... ;-)
Be careful of your newly germinated seeds with the forecast extreme cold at the end of Feb / start of March! WEATHER/ METEO WORLD on Twitter
I check the weather forecast every day, and Météo France is not that bad. I've been off to the atlantic coast for a week. But I don't have a greenhouse, so that meant either putting the sprouting seeds in the garage or leaving them outside. In the garage, they would have dried (the average temperature is that of a wine cellar, bout 13° C) , or rotted if I kept them in a tray wth water. So I left them outside, but added 5-10 cm of cocoa shells on top of them: We'll see: just got back home and it's dark outside. Last night in Rochefort, it was -7°C, and when I left at 2 PM, it was 14°C, and the snow had not melted everywhere. 21°C difference in 12 hours: crazy weather!
Maybe I was about too optimistic about leaving the sprouting seeds outside : Yesterday, it was warm again, here about 10° and rather sunny, and I went to buy some composted pine bark and other. To my surprise, if the top 5 cm of the huge mound of composted bark was soft, there was a layer of 3-4 cm that was frozen. This afternoon, at about 4 PM, there was still a 2 cm layer of ice in the middle of a 15 cm high tray. Wow! I still had some Acer morifolium and Acer rubescens in the fridge, and I could see some yellowish green roots showing, so I decided to put them in a planting tray. No frost in the coming 2 weeks according to the weather forecast. The mix is... mixed: I re-used some that was left (sand+peat) and added the bottom of a bucket I used for bonsai (akadama, pozzolane, pumice, about 5 mm), then added composted bark pine and a bit more pozzolane (5 mm). I then put what was left in the bags. On the 3rd picture, you can see a small root next to the center of the picture, on the right, there were a few others. I added some soil mix, and then a layer of pumice: when I take them outside, I hope the blackbirds won't dig into the soil. It's also more convenient to water without the soil being disturbed too much. I will keep them in the basement/garage where the temperature is about 13° all year round, and when I take them out, I will spary cinammon on the tray: good organic treatment against cats, critters and fungus.
Great pics to show methodology, sorry if your morifolium/rubescens didn't survive. I have a handful of rubescens going into the second season, will be happy to send you, if you don't get any. I've brought them in to a windowsill, along with these new pseudosieboldianum subsp takisimense. These are germinating in the second year, I got nothing the first year. It's quite common for me, and I always keep seed trays at least 2 years as a result. cheers, -E
