Which seeds need freezing?

Does anyone know? Jackie
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In general summer-blooming annual flowers, perennials such as lettuce, trees and shrubs from temperate climates usually need stratification which involves soaking and chilling (NOT FREEZING) seeds prior to sowing. This simulates natural conditions where the seeds would remain through a winter on cold, wet ground . Seeds will usually germinate promptly and uniformly after stratification. Unstratified seeds may take up to two years to germinate, if they do so at all.
Many tree seeds have what is called an "embryonic dormancy" and generally speaking will not sprout until this dormancy is broken. In the wild, "seed dormancy" is usually overcome by the seed spending time in the ground through a winter period and having their hard seed coat soften up a bit. By doing so the seed is undergoing a natural form of "cold stratification" or pretreatment. This cold moist period triggers the seed's embryo, its growth and subsequent expansion eventually break through the softened seed coat in its search for sun and nutrients.
In its most basic form, when we control the cold stratification process, the pretreatment amounts to nothing more than subjecting the seeds to storage in a cool (not freezing) and moist environment for a period found to be sufficient for the species in question. This period of time is often and usually found to be somewhere between 1 through 3 months. The crisper in a refrigerator is usually ideal.
The amount of time needed for cold treatment varies. Seed of cedar of Lebanon, which will stay viable for six months, only need two months for stratification. Plants like alder and chestnut need three months; shadblow, horse chestnut and shellbark hickory need four months. A few plants need both a warm and a cold period of stratification: cotoneaster bearberry, dogwood yews and some of the barberries and junipers. Some lilies, viburnums and the tree peony all need a spell of moderate temperature followed by cold. Unless kept in the refrigerator such seeds are planted during the summer, kept moist, and allowed their cold dormancy during the following winter.
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Great info. Would you have any idea about getting American Mountain Ash seed to germinate? I have picked these seeds from trees growing in the wild in Northern Quebec (zone 2/3). Thanks

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According to: http://www.macphailwoods.org/shrub/montash.html
Gather berries in late September and remove pulpy flesh by hand. Each berry contains up to 10 tiny seeds. Plant in nursery beds and cover lightly with soil. Seeds will germinate the second spring and grow quite quickly. At Macphail Woods, our first year's growth averaged 16 inches (40 cm).
however according to: www.mnr.gov.on.ca/mnr/forests/ public/otspE/seedcatalogue.pdf
if you stratify for 60 to 90 days before planting, they should germinate the first year.
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Stephen thanks for those links! Will try planting some seed this fall in the garden. I found Mtn Ash growing wild and was very impressed by their color and foliage in autumn: huge plumes of bright orange and red berries. Seeds are now 2 years old but will try anyway.

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Nobody knows, dearie. Its one of the unsolved mysteries of the universe. ;-)
Sheesh, why do you even ask such a question?
Of course there has been much research on the topic and many books written including lists of such plant seeds and what is needed to break dormancy.
Betcha, if you do a Google search you will find many websites on the subject too!!!!!

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