How do you know if seeds need stratifying?

When you buy seeds from garden centres readilly packaged, have they already been stratified and prepared? If I collect seeds from a plant in my garden, should I stratify them? Does it depend on the species? Peonies, for example, I hear need fully stratifying and a period of warmth before germinating.

Or does it only apply if you want to sow the seeds at a time of year unnatural for them?

 

You look it up. :D

When you buy a packet of seeds they won't generally have had any pre treatment. Its my understanding that stratification, ie a period of cold treatment prior to sowing, only works when the seeds are damp. And when they are damp they will either germinate reasonably quickly or rot. So you can't pre stratify a packet of seeds without ruining its shelf life. However, you can store many seeds in the dry in a deep freeze where they can remain viable for tens and sometimes hundreds of years, but thats not stratifcation because it dry. Incidentally, you should stratify in the fridge, ie at about 5C, not the freezer.

Most seeds don't need stratification. Its only some types. Its done to try to recreate the conditions that the seed would experience before germinating in its native country. The seed needs this pretreatment so that it 'knows' that its the right season to germinate. If the seed was able to germinate at any time, it might do it in the middle of a very hot dry summer and consequently die.

I looked in my seed germination guide and a few common seeds that need cold stratification are :-

Allium, Astrantia, Clematis, Cleome, Corydalis, Dicentra, Echinacea, Euphorbia, Fritallaria, Helleborus, Lavandula, Leycestaria, Lillium, Linaria, Lonicera, Lychnis, Malus, Mimulus, Primula, Ranunculus, Verbena and Viola.

There are quite a few others, and some shrubs/trees need both cold stratification and warm stratification too. However I have germinated several of the above without cold stratification, though I am sure I would have done better with. Curiously, my guide doesn't mention it for Paeonia, it just says may take more than a year!

 

I go along with that Peter.

As I understand it peony is one of those strange seeds that grow a root well in advance of any shoot, possibly a root one year and a shoot the next.
I think this is why a colds spell followed by a warm spell then cold again is sometimes advised.

I've germinated peony seeds by just planting in autumn and waiting, some seed will show the first year others may take two years.
But you need patience.

 

Pete are there any guidelines as to what needs stratifying? I like to understand why things happen, simply because my memory has always been so bad since I was a kid that I could never remember lists of things, I was all I could do to remember just a single principle.

I would be nice if all early flowering plants from cold climates needed stratification, but I don't think that is true, and I don't see any obvious connection between the plants I mentioned above.

 

I'm not sure Peter, my own personal thoughts are that if its a hardy plant species it would probably benefit from stratification.
If its seed bought from seed suppliers and they dont mention it, its probably not necessary.

But I would stratify all hardy shrub and tree seeds with a hard coat, but I dont think there are hard and fast rules you can follow as seed is a natural substance and has a way of not following the rules we make.
Germination in its self can be as complicated or easy as you like to make it.
The expert can spend hours getting the preparation right, and somebody scattering the seed on a seed tray could have better results.

My main thought is fresh seed, if its fresh it will germinate, many seed companies seem to hide behind this strange idea that seed is hard to germinate.
My guess is that many are just selling old seed and hoping we blame ourselves for not getting the germination process right, when nothing comes up.

that said, some seed can take a bit longer than cress.

 

Thanks Pete - that makes sense. I don't generally grow trees or shrubs, but I was amazed at how many in my seed germination guide said both cold and warm stratification - you are quite right.

And, yes, I have seen reports that some seeds sold by seed companies are totally dead when sold. I just hope its not a large proportion.

 

I didn't even know what stratifying was :o

 

Vicki - its a bit of a silly word really - its not very obvious what it means.

 

Well - at least it's one less thing I need to worry about. Ignorance is bliss! :hehe: