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What is the deal on cold stratification?  RSS feed

 
Posts: 20
Location: Middle Georgia
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I am an inexperienced gardener and am hoping to plant a few medicinal herbs this spring, a couple are difficult to germinate (Elecampane and Ephedra sinica).

So after researching it appears cold stratification is recommended to increase germination rates. Thing is there is often no mention if they should be stratified in the fridge or the freezer, and if that means just the seeds, or if they should be moistened and kept on a bit of soil mix. I know some seeds, like poppies, just need a quick freeze in ice cube trays to crack the shell and germinate, and I am not sure if that even counts as stratification but I have read the elecampane seeds are often stratified in the freezer for several months.

Right now I have a couple of seed packs in the freezer which seems safe since people frequently do that to store seeds, but they are stored dry so it may not even count as stratifying them if they need to be in a soil mix. I paid $8 for 20 precious little Ephedra seeds and most say they are lucky to get one out of 30 seeds to even germinate, so I am trying to do what I can without a whole lot of experimentation.

Any tips or advice on this whole stratification business? Despite googling it does not appear to be easy to find specific info on how to do it, what plants like cold vs. frozen, and to make matters worse there isn't a lot of specific growing info on these species.
 
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My advice would be to find out where the plants are native, and try to mimic the winter conditions found there.
 
gardener
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Usually when you want cold stratification, you want it in a moist growing medium at or around freezing to mimic winter time conditions. I'm still learning a lot of this myself, but this year I plant to put a bunch of seeds in a moist sand mix and leave it in my garage all winter. Last winter I assumed dry seeds in cold weather would stratify them, but that was not very successful.

In my own research, it really deeply depends on the specific species, and even then stratification is all about increasing chances of  germination. No stratification may germinate 10%, while a cold stratification may germinate 60%, but scarification and a cold stratification may germinate 95%. For example this guide on growing Ephedra has this complicated bit on germinating the seeds:

In experiments with 6-month-old seedlots, 7-day germination for unchilled seeds at 10 to 20 °C was 10% for 1 lot of green Mormon-tea, 49 to 54% for 2 lots of Nevada Mormon-tea, and 95 to 100% for 3 lots of Torrey Mormon-tea. The 7-day germination after 2 weeks of chilling at 1 °C was over 90% for all seedlots. Germination is generally highest at temperatures of 15 to 20 °C, except in more dormant lots, which show higher percentages of germinatation in temperature regimes that include a temperature in the chilling range (Young and others 1977). Germination is suppressed by higher temperatures, which probably prevent the otherwise nondormant seeds from precocious summer germination. Ephedra seeds germinate readily during prolonged chilling. Kay and others (1977) reported 76% germination during a 30-day stratification at 2 °C for a Mojave desert collection of Nevada Mormon-tea. In chilling experiments with the 6 seedlots mentioned above, weeks to 50% germination at 1 °C varied from 6 to 7 weeks for the Torrey Mormon-tea collections and from 8 to 9 weeks for collections of the other 2 species. All viable seeds germinated during chilling within 12 weeks.



Good luck! I might suggest trying a few different methods of stratification instead of putting all your eggs in one basket. 20 seeds isn't a huge number, but it's enough to try a couple of batches at least.
 
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Stratification is supposed to mimic what happens in nature.

Sand is the preferred medium to use when stratifying seeds since it will keep the moisture level more constant than other mediums.

There is a huge list of plants and their conditions, needs at the USDA website along with other sites. Look up your desired plants there and see what conditions they prefer/need to thrive.
From that point all you have to do is mimic those conditions to properly stratify the seeds.

NOTE: most plants drop their seeds in the fall, these seeds then lay dormant over the winter and sprout at the right time in the spring.
The easy way to mimic nature is to follow the same path, plant in the late fall, they will come up in the spring.

If the seeds were designed to pass through a gut system then you need to scarify (scratch the surface) so the seed can break through the seed coat that was designed to be softened by stomach acids.
If the seed is from a plant that experiences cold, snow covered winters, then you would need to put them in a freezer. If they grow in a place that doesn't get hard freezes then the fridge is where you need to put them.

Redhawk
 
Lucrecia Anderson
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Kyle Neath wrote:
In my own research, it really deeply depends on the specific species, and even then stratification is all about increasing chances of  germination. No stratification may germinate 10%, while a cold stratification may germinate 60%, but scarification and a cold stratification may germinate 95%. For example this guide on growing Ephedra has this complicated bit on germinating the seeds:



Thanks, I searched and came across a lot of articles but didn't see that one and it is the best, all the other info I could find was personal experience posted on bulletin boards.

Wow that is a bit complicated, had to read it a couple of times to make sense of it. From what I understand they will germinate DURING stratification if the temps are slightly above freezing, so I had best wait until it is closer to planting time. Will put 10 of the seeds in a jar with some moist sand, heck will probably scarify them ahead of time just to be extra safe.

Apparently the plants all fruit at once, and then may not fruit for several years, so that no doubt explains why the seeds are so pricey. I ordered 20 seeds off ebay and that is exactly what I got, not 21 seeds, but exactly 20. LOL. But because of recent regulations the seeds are VERY hard to find, I just hope the seller is honest and sending seeds for the advertised species.

FYI if anyone is interested, Ephedra sinica contains the same chemicals found in asthma and cold/flu meds (ephedrine and psuedoephedrine) so it is a good addition to a prepper herb garden.
 
gardener
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My strategy towards cold stratification is that nature does it better than a refrigerator or freezer, so I just plant things in the fall, winter, or super early spring, and let mother take care of it in her own way.

 
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I'm not sure if this is helpful....I have little knowledge on stratification....I just know that I need to do it for certain seeds.

There is a time element involved with stratification from what I recall.  There is typically a minimum number of days to keep the seeds moist and cold.  I'm recalling that 90 days is a general number with higher degrees of success, "for trees at least".

But like I said.....I'm not very experienced with this specifically....I'm like Joseph...I just put the seeds in the ground/soil outside.  I've yet to use the fridge for stratification, and my experience in general with it has been quite limited.
 
Lucrecia Anderson
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Joseph Lofthouse wrote:
My strategy towards cold stratification is that nature does it better than a refrigerator or freezer, so I just plant things in the fall, winter, or super early spring, and let mother take care of it in her own way.



While that would be ideal it isn't an option. I am not planting in weed free raised beds, but have a small garden carved out of a natural grass field that has been fallow for at least 10 years.

The grasses, indigenous plants/weeds and cutworms are extreme (though this spring I will use Bt, didn't know about it last spring). I like to sprout indoors or grow indoor transplants so I can identify the plant when it goes outdoors unless it is an obvious fast growing crop.
 
Joseph Lofthouse
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You might try pots outside with weed-free potting soil. You might try the winter-sown method. You might leave the pots outside for a month or two and then bring them inside, etc...

Last time I sprouted hazelnuts, about 8 seeds sprouted the first spring, and about 40 sprouted the second spring.
 
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