How to Attain Various Germination Temperatures?

I have a variety of seed packets to be sown in the coming months, and I have been making a list of what conditions they need and when to sow them - so I can make a little reminder system and ... hopefully! ... screw up less than normal!

I've broken them down into a number of germination temperatures that are recommended, and they are quite variable (and some are quite narrow-band)

10-15C - quite difficult that, we have a utility room that is not heated, that will probably do (Delphinium x cultorum). I'll stick the Max/Min thermometer in there and see what it says
15-20C - that's easy, our house heating is in that range
20C -25C - that's probably what I get in my windowsill propagator (gentle bottom heat, no thermostat)
24C-27C - that's really narrow-band - ideas? How fussy is it? (Verbena bonariensis)

Some are wider band - e.g. 18C - 29C - (Digitalis purpurea) presumable the house will do for that (although it might nudge below 18C), or the propagator

20C-30C - strikes be as quite hot at the top end, but the propagator will do (Petunia grandiflora - but the other Petunia grandiflora varieties I have ordered are 20-25C - could be a misprint I suppose :( I'm starting not to trust them, especially as a few of them have completely different C and F values - which do I trust? :( )

How fuzzy do I have to be, and in particular is it important to stay within the band? (e.g. on the Windowsill propagator if the sun comes out the little seed trays with clear plastic domes might get hotter I reckon?)

I can stop them getting colder, it would only be hotter that I think would be a problem.

23F - freezer? (the cold phase for Veratrum nigrum) I've never seen a cold phase that low, its always been Fridge temperatures.


I'm stuck on this one:

Suttons Sweet Peas 13-16C
T&M Sweet Peas 20-25C

they can't both be right?!


Helleborus purpurescens (T&M)

"After sowing place container in a bag and leave at around 20C for 3 months, then place container and bag into a fridge for a further 3 months"

I'm OK so far ...

"Germination can be slow, examine container regularly and carefully transplant individual seedlings to 3" pots. If germination has not occurred within this period then repeat the cycle as shown above"

So germination will occur in the fridge during the cold phase, and not during the (possibly repeated) warm phase? (No problem if it does, I can handle that!, just seems odd that germination will be in the fridge!)

 

Perhaps a heater with a thermostat that could maintain the temperature of a room would be ideal?

I didn't realise Verbena bonariensis required such a high temperature. I was just about to order some seeds of it too, I think you've saved me a job because I would struggle to be able to provide such a temperature, never mind maintain it with accuracy. Maybe another member can tell you (I should say us) how fussy they are when it comes to specifics.

 

Kristen, over the years I have come to miss -trust most germination temperatures given.

Call me an old sceptic but with most seed, if its good and fresh, it will germinate at a wide temperature range, it might take a bit longer, but it will come up in the 20-25 range for anything half hardy.
Most hardy stuff will also germinate at that range.

Of course there are exceptions, stratification etc. for certain seeds, and maybe a higher temperature for the real tropical types.

I always put the suggested germination temperatures down to the seed companies covering their backs, that way, when they sell you dead seed, you will end up blaming yourself when it doesn't grow.

Unless its something a bit obscure I cant see special temperatures are needed, nature doesn't work like that.

 

Hi Kristen. I think there is such a thing as being too fussy and some of what appears on seed packets is nonsense.
I only work in 3 temp bands - cool, warm, hot.
Cool - I put in an unheated space
Warm - in a room where we are living
Hot - in the boiler room.
That system works for me.
And everything germinates more quickly than the times given on the packets.
Oh, I sing to them too -

 

Thanks folk.

That's what I've been doing for years. In fact I never used to look at the germination temperature on the packet, it just went in the propagator.

Then I discovered (well, "read") that some things don't like a lot of temperature - found that hard to believe at first; I mean, I like to be toasty-warm given the chance!

But now I raise my brassicas in the Spring without using heat, and as soon as they are germinated they go outside rather than languishing in the conservatory. They grow slower (which felt "wrong" at first) but stronger.

But whilst recording the requirements of the (quick head count ...) 60 or so packets of seed on the desk in front of me (and there are about 60 or so already stratifying in the fridge ... plus another 60 or more "Veg" ... do you think I've overdone it?!) I started to wonder whether some of the things that have failed in the past have been because I didn't pay enough attention to the packets.

But I like the sound of Cool, Warm, Hot. I haven't had to do a HOT before, and we don't have a boiler room, but I am sure I can conjure something up when the time comes.

I think I'll look up the "odd" / narrow-band ones on the internet to get a second opinion ...

HBK: If I managed to get a handful of Verbena bonariensis going you can have some. But if I fail then its your turn next year !!

 

I'm not knowledgeable enough to give a good answer, but I have some experience with some of the plants you mentioned.

Digitalis purpurea, isn't that the native Foxglove? If it is then I've found that as long as the compost never dries out, they just get on with it and grow. I've also had a lot of success with them just throwing the seeds on the floor (granted that strategy only gives a few plants per packet of seed but it shows that they're not too fussy).

Sweet Peas, don't you just soak them overnight and then sow them indoors? My dad has loads of them grown that way.

Incidentally, I saw on TV (or might have read somewhere) what the Victorian botonists did in the absence of modern propagators. They built a 'hot bed', which was just a big container of fresh horse manure, a layer of straw on top, then the seed trays on top of that. The heat generated by the manure rotting provided bottom heat for propagation. It clearly worked as it was in that era that most of our garden plants were cultivated, and I imagine the heat from a rotten compost heap is very variable.

 

Hi Kristen, Just to clarify the boiler room bit -
my boiler room is really a box room which has the gas boiler in it.
It gets very warm in there - 25 degrees plus.
But anywhere beside a radiator would do just as well.
I've found for some things - primulas and the likes - too much heat spoils germination as much as too cold does for some things.

 

Yup. I agree, it self seeds quite happily. I'm growing some fancy cultivar, so few seeds in the packet, and I am greedy to want as many as possible to germinate :thumb:

"Sweet Peas, don't you just soak them overnight and then sow them indoors? My dad has loads of them grown that way."

Me too! I was just curious that Suttons and T&M had such wildly different instructions.

"the Victorian ... built a 'hot bed', which was just a big container of fresh horse manure"

at a tangent:

I think there was a self-sufficient bod who got a large (50 tonnes, 100 tonnes maybe?) of wood and put pipes through it and heated his house from it for years.

The Victorian Kitchen Garden series had a manure "culvert" next to the melon house. That provided the heat. If memory serves me it was 40 tonnes of manure, and had to be changed every couple of months - and the "culvert" it was in was brick lined and about 10 feet deep - all had to be dug out by hand!

But you are right, given the temperature from composting process, and enough time & labour to maintain the beast, and that would indeed do the trick.[hr]

Yup .. we had one too. But now we have a log burning boiler (all very "Eco" here now) and that is in the garage, its so well insulated there is only a tiny leakage of heat, and the garage is freezing anyway!

I can sort something out "toasty" if I need it though, I'm sure.

Many thanks.

 

I've got the paprika seeds in a pot on top of the woodburner, separated by a bit of wood of course. They apparently need 27c to germinate. No sucess yet.

The tea is sat above them in a pot inside a plastic bag, has been for months, nothing going on there either.

 

You need to light the woodburner

 

I am afraid I have never taken any notice of the suggested temps.I have one good propergator and when it's full....it's full and they all get 23C.ish.
When they are germinated they come out.
So this is proberbly the reason I have the odd failure.
So unless I have several propergators on the go I would find it difficult.
Also the vents are important,they do let hot air out.......This imo is the key.
I am taking this info on board though.:thumb:

 

Useful exercise for me too ... I have discovered that we have an airing cupboard that is "toasty" - so that's my "hot" taken care of (well, until germination anyway)

 

Ahh Kristen I wish you'd said that earlier, I bought some seeds yesterday. It would have been a great idea. I don't want all that many though so perhaps I could share with you?
Edit: Did you mean seeds or seedlings?

As for the heat, I recently grew morning glory from seed in my bathroom, I know it won't grow well, if at all now, but I just wanted to experiment. The idea was that the steam from the bath would heat the plant and the half-a-bottle over it would maintain some warmth.
Then again, I don't know how constant the heat would need to be for a seed to germinate. In my mind I would imagine it can't be that strict with night and day, etc.

 

I was meaning plants, if I germinate get enough to share - I haven't looked at the packet, there might only be 5 seeds in there?!

If the packets have plenty of seeds and we are both having a crack, then one of us should have enough to share at least :thumb:

Morning Glory grow like weeds don't they? I've never had a problem with them (probably started them in my no-thermostat propagator though ...

 

Like Alice , I divide my seed sowing into 3 bands...
The majority 20°c - 25°c go into my windowsill prop
Warm 16-20°c in a living room
Cool in the spare bedroom
Thats the best I can do to control the temps for the seeds . I have a seed planting Excel sheet so I can plan my sowing logistics for the prop. I also note germination time and percentage on this, and as Alice said for the majority of times it is usually quicker.
This site below , has an enormous amount of info on seed germination , and unless I have missed a page he never seems to mention an accurate germination temperature. Maybe we are being a bit to fussy ?

http://theseedsite.co.uk/
(why do links not work now ?)