Seeds that need stratifying

[Garden Manager]

For those of you who arent sure what this means, its seeds that need a period of cold in order to germinate.

I need some advice on the seeds of some perennials that need stratifying to germinate them. I want to grow a few of them now but now we are into march it is becoming less likely that we will get a decent cold snap to do the job. I was wondering firstly how much cold was really nessesary and if simply not protecting the seeds on colder spring nights would be enough.  That way I could sow as normal and just put them in a sheltered spot. Secondly is it worth refrigerating the seeds to mimic a cold winter and if so what is the best way to do this. I only have a small fridge so cant put whole trays of seeds and compost in it! I was thinking of mixing the seed with vemiculite inside freezer bags and placed in an airtight container, to save space.

Can anyone advise me please.

[Garden Manager]

[star]

I guess the vermiculite with the seeds in the fridge would work, I think 3 weeks is about right. But someone far more knowledgeable will tell you exactly the way about it :D

[morton]

Tried and tested method from my distant past is to put the seeds in equal parts by volume of peat and sand in a glass container and put in a fridge at 2 to 4 degrees centigrade for around 6 to 8 weeks.

[Jeannine]

oh thank you for this post, I have a bag with cranberry seeds in compost that has been in the fridge for 6 months, that is what the directions were, I remember that vividly, but I have seen lost the paper and don't know what to do next. The seeds were like dust theywere so small so no chance of picking them out of the soil. Does anyone have any ideas please ? XX Jeannine

[star]

You could fill a seed tray then sprinkle the contents of the bag on top. Then cover that with vermiculite

[Jeannine]

I seem to think it said sow late winter and I agree your idea seems best

[caroline7758]

Quite  a few of the seeds I got from the RHS seed distribution say they need stratification, yet other suplliers don't mention it. I know the RHS should know best, but it seems a bit of a palavar (?) to me, so I'm going to try just putting them outside when I've sown them!

[Robert_Brenchley]

Plant them in a pot, put it in a cold frame somewhere, and neglect them till they either come up or not. Plamting seed that needs stratifying too late usually means a 12-month delay, but it does come up in the end.

[DenBee]

Reading this thread I thought - what a nuisance, I shan't be buying anything that needs stratifying.  Then opened a mini propagator pack of alpine strawberries I got yesterday at Home Bargains, and found instructions to put the seeds in the freezer for 2 - 4 weeks.  ::)  ;D

[Garden Manager]

i should have said that thse seeds are courtesy of the RHS too. The plants in question are Euphorbia characias, hardy geranium (phaeum and sylvaticum i think) and polygonatum (solomons seal). I also plan to sow some eupatorium (joe pye weed) and perennial sweet pea. These last two dont appear to need actual stratifying but seem to need cool environment to germinate.

With the forecast of night frosts this week i am tempted to follow robert's advice and just sow them and stick them in the cold frame with minimal protection.

Putting them in the fridge sounds good in theory, since it should speed things up but there is the danger i might forget them and they never get sown! Plus like jeannine says there is the problem of extracing the seed from the stratifying medium in order to sow them properly.

I guess where I have enough seed i could try both methods.

I do remember once growing some carex from seed. These too needed stratifying, but i got them to germinate more by luck than by judgement. I sowed the seed in a pot and gave it plenty of TLC for a few weeks. Then when nothing happened I all but gave up and forgot about the pot for a while. Some time later I looked at the pot and saw all these grassy seedlings had come up. They are now mature established plants in the garden. Just shows some seed doesnt need to be fussed over to germinate!

Perhaps i need to do this with the seed i want to sow now?

Thanks for the advice.

[kenkew]

I have a bit of detail on Euphorbia.
Sow at 15deg c in spring. Germination can be erratic and seedlings will pop up over many months. To combat that, sow fresg seed in autumn and expose to winter cold. Seeds should then germinate more evenly in spring.
Plants take 2/3 years to reach full size.
I should think a few weeks in the fridge in a poly-bag mixed with damp vermiculite would have a similar effect.

[Garden Manager]

I am now rather confused. I have looked elsewhere and like someone said each supplier says something different.

i have checked my 'stock' and found I have 2 packets of the euphorbia nd the geraniums so may have to use both to try out different methods.

Thanks again

[Tee Gee]

There is merit in all the methods mentioned here.

The purpose of the 'stratification' is to replicate the plants natural reproduction process.

In the wild i.e. the seed is strewn over the ground and is sometimes covered with fallen leaves or dust that has blown over them.

They remain this way through winter i.e. through frost and snow then they germinate.

Some years there is a good reproduction rate and other years there is not, by looking back you will generally find that one winter was milder than the other.

Now you can see the similarity with all the suggested methods.

[Kea]

Different species require different lengths of stratification it depends on where the plant is indigenous to each has it's own optimum. However some chilling will speed things up even if you don't hit on the optimum for quickest germination. For example I can tell you that Clematis vitalba seeds chilled for 2 weeks took twice as long to germinate as those chilled for 6 weeks, however the time taken overall to germinate was about the same.

[Robert_Brenchley]

Just to make things more complicated, some plants (Paeonies, Trilliums) sit through the first winter, then produce a root. They then sit through the second winter, and finally produce a shoot.

[Kea]

Nature is much cleverer than us it does things the way it does for a good reason we just have to be patient.

[Garden Manager]

Just to make things more complicated, some plants (Paeonies, Trilliums) sit through the first winter, then produce a root. They then sit through the second winter, and finally produce a shoot.

So thats why some seeds need stratifying twice. To trick them into thinking they have had 2 winters. Ingenious!