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Old 10-09-2016, 07:15 AM   #1
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Default Double dormancy

I've never tried to germinate seeds with double dormancy before, so I'm looking for any input. I've got Actaea pachypoda and A. rubra seeds in the fridge now. They're in plastic bags with slightly moistened potting mix. They've been in there about a month, and my current plan is to pull them out in December, giving them three months of cold stratification, and put them in winter-sowing-type containers indoors until March, then put them outdoors for a bit, and once it starts warming up in mid April, back in the fridge until June. Then remove, put outdoors, and wait for germination.

Any thoughts on cold-warm-cold stratification or these species in particular?
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Old 10-09-2016, 03:08 PM   #2
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Welcome back!

I don't have any experience germinating baneberry from seed, but this summer I collected some red baneberry seed and I'm going to try it this year.

Here's some info that I found in "Seed Germination Theory and Practice" by Dr. Norman C. Deno.

"Actaea (Ranunculaceae).

The seeds are enclosed in a berry and were given an initial washing and cleaning (WC) for 7 days. Germination took place at 40, but only after one or more prior cycles. The radicle develops at 40 to a length of 2 - 3 inches after which growth stops. It was found that an immediate shift to 70 when the 3 month cycle at 40 was over led to total rotting of the radicles and death of the seedlings. Some success was achieved in getting the cotyledon to develop in A. pachypoda and A. rubra by keeping the seedlings for 4 months at 40 after radicle development was complete. A shift to 70 now gave cotyledon development with about half of the seedlings. It is suspected that in order to get efficient development of the cotyledons it would have been better to raise the temperature from 40 to 70 gradually.

...

A. pachypoda germinated 40 - 70 - 40 (85 - 90% in 3 - 6 weeks ... ) using fresh seeds and 70 - 40 (85 - 90% ... ) using seeds that had been dry stored for 6 months at 70 or 40. It is curious that 3 months moist at 40 and 6 months dry stored at 70 had the same effect, and either one or the other were necessary for germination in the 70 - 40 pattern. Other treatments have more extended germination as shown by 70 - 40 (52%) - 70 - 40 (46%) for fresh seed. After the radicle has completed its development, the seedlings must be kept an additional 4 months at 40 before being shifted to 70. Even then only 50% of the seedlings develop their cotyledon normally, and it is suspected that a more gradual increase in temperature would have given better development of the cotyledons. Treatment with GA-3 had little effect. Seeds placed outdoors in August germinated 25% in November and in March and April.

A. rubra germinated 40 - 70 -40 - 70 - 40 - 70 - 40 (24% in 5 - 7 weeks) for fresh seed, 40 - 70 - 40 (18% in 4 - 6 weeks) for seeds dry stored 6 months at 40, and 40 - 70 - 40 (4%) for seed dry stored 6 months at 70. When started at 70, germination did not start until the 3rd to 6th cycle and was overall only 4% for both fresh and dry stored seed. All seed that not germinate ultimately rotted. Difficulties were encountered in getting the cotyledons to develop. The discussion under A. pachypoda applies here."

If you are not familiar with Deno's method here's a quick explanation. To get seeds to germinate he places the seeds in moist paper towels that are then put in plastic baggies. He then puts the plastic baggies in the fridge (40) or in a heated room (70) for a specified time (usually 3 months). For example, 40 - 70 - 40 means 3 months in the fridge, followed by 3 months at room temperature and then 3 more months in the fridge.

He goes into a lot of detail and has an interesting theory about seed germination in his books. His series of books are downloadable for free, I think the links to the books are somewhere here in the forums. As far as I know they are no longer available in hard copy.

I like the final thought he put on the cover page:

"To Plant a Seed is a Noble Deed
Propagation is Conservation"
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Old 10-09-2016, 03:28 PM   #3
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Thanks!

Wow, that sounds complicated. How in the world am I to raise the temperature gradually from 40 to 70? I could move them in and out of the fridge every day, I suppose, but that's hardly workable over several weeks. Perhaps I need to find a cooler spot in the apartment (over the winter it will likely be mid-60s indoors, but that's presumably still too big a shift). Anyway, thank you for the tips. If I get even 30% successful germination and cotyledon development out of these, I'll be satisfied.
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Old 10-12-2016, 12:01 PM   #4
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Yes, Deno does explore a lot of complicated options. In my case I think I'll try to time things so that the "gradual increase in temperature" phase would start in early spring. That way I can place the seed into the cold spring soil outside and let nature do the gradual increase in temperature.

That's not an option available to an apartment situation, but as you say 30% success is still a nice outcome.
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