Warm germinators and Cold germinators

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RickR
Title: Moderator
Joined: 2009-09-21
Warm germinators and Cold germinators

Dr. Deno writes in his book Seed Germination Theory and Practice:

Quote:

Germinations also tend to take place either in the 40[°F] region or the 70[°F] region of
temperatures. However, with germinations the division is not so complete. Examples
were found where germination would take place at both 40 and 70.

So I have always thought the definitions of the terms "warm germinator" and "cool germinator" would be straight forward:
--- warm germinators are species that germinate in the 70F region.
--- cold germinators are species that germinate in the 40F region.
This corresponding to the temperature spurring actual seed germination (not necessarily the emergence above ground) and being regardless of any pretreatments.

And to be more precise, I would designate thusly:
--- cold/warm germinators: seeds that require cold conditioning prior to emergence in the ensuing warm conditioning.
--- warm/cold/warm germinators: seeds that require warm conditioning, then cold condition, before they emerge in the ensuing warm conditioning.
--- warm/cold germinators: seeds that require warm conditioning before emergence in the ensuing cold conditioning.
--- Etc.

I was quite comfortable with my way of thinking, until Lori came along with a different point of view:

Lori wrote:

Rightly or wrongly ... I've always assumed that "warm germinators" were just those that don't need fluctuating temperatures to break down germination inhibitors, not that they actually need warm temperatures to germinate... ?

In my mind, I would call those easy warm germinators if they germinate in the 70F region, and easy cool germinators if they germinate in the 40F region. Dr. Deno mentions the term "immediate germinators" for seeds where simple drying overcomes germination inhibitions, but does not endorse its use.

Gee, we really need to be all on the same page here, and I would happily change my personal definitions to fit the prevailing thought.

So, what are the generally accepted names for such scenarios?

cohan
cohan's picture
Title: Guest
Joined: 2011-02-03

I probably have a more or less similar set of terms in mind, but always being aware of (perversely fond of?) the complexity in nature, I don't really expect too many plants to always or tidily fit into one of those categories.
So many issues with freshness, for example-  plants that germinate immediately if fresh, and need temperature cycling if older, and those that germinate best if older and need pretreatment if fresh, those that germinate promptly no matter what, those that seem designed to have staggered germination over years etc.....

west central alberta, canada; just under 1000m; record temps:min -45C/-49F;max 34C/93F; http://picasaweb.google.ca/cactuscactus  http://urbanehillbillycanada.blogspot.com/

CScott
Title: Member
Joined: 2010-02-23

I think that one has to get to know each seed and each plant, rather than making generalized classifications.
And each of us has slightly different growing and germination conditions available.
Some seeds like those of Iberis semperflorens will germinate at both 4ºC and 20ºC.
It is especially aggravating that some recent "Gardening" books appear to not have heard of Dr. Deno's work.
Dr. Deno gave us a good start on understanding the various possible germination proceeses.

RickR
Title: Moderator
Joined: 2009-09-21

It has always been my contention that the only unbroken rule in nature is that "There are no unbroken rules.". 
That there is variation in germination within a species is indisputable. It would be ridiculous to think that varying environmental conditions have no bearing on outcomes. 
But most seeds within each of most species do behave a certain way. 

Categories are humanly derived entities, and by that very definition cannot perfectly describe nature, including germination.  I am not disputing this, nor is that the subject I want to pursue here.    We do our best, with categories, however imperfect.

But again, this is not why I began this topic.

When one person calls a certain species a warm germinator (for instance), and another person calls it something else ....
THIS is what I hope to clear up.  Which definition is correct?

RickR wrote:

Gee, we really need to be all on the same page here, and I would happily change my personal definitions to fit the prevailing thought.

So, what are the generally accepted names for such scenarios?

It is the standard definitions of the germination modes that I hope to determine.  Discussing whether a species fits a certain germination mode is another subject entirely.

Rick Rodich    zone 4a.    Annual precipitation ~24 inches
near Minneapolis, Minnesota, USA

Lori S.
Title: Moderator
Joined: 2009-10-27

Errr, since it seems this thread was spurred by my somewhat offhand comment (

Lori wrote:

Rightly or wrongly ... I've always assumed that "warm germinators" were just those that don't need fluctuating temperatures to break down germination inhibitors, not that they actually need warm temperatures to germinate... ?

), I guess I'd best clarify....
I was just referring to the climatic conditions around here, and the point that we'd already agreed on about Dr. Deno's experiments being standardized at particular temperatures for scientific integrity.  On the first point, "warm germinators" germinate on their own outdoors here in spring despite that it may only reach 20 deg C for a few hours in the day (and almost never remains that warm through the night).   On the second point, "room temperature" is a convenient standard but in his discussion about heat mats, Deno points out that there is no particular magic associated with exactly "70 deg F".

Anyway, I didn't intend to create any controversy.  
I have no disagreement with your definitions, either - they look fine to me.  :)

Lori
Calgary, Alberta, Canada - Zone 3
-30 C to +30 C (rarely!); elevation ~1130m; annual precipitation ~40 cm

RickR
Title: Moderator
Joined: 2009-09-21

Not a controversy at all, Lori.  Yours is exactly the discussion I hope for here.  Your initial remark, that
I've always assumed that "warm germinators" were just those that don't need fluctuating temperatures to break down germination inhibitors, not that they actually need warm temperatures to germinate... ?
made me wonder if you would then consider seeds that germinate at a simple 40F regime as "warm germinators", because the temperature was non-fluctuating.  Thanks for clearing that up.
-----------------------------------------------------------------------
And already now, I must point out a flaw in some of my  multiple conditioning definitions. For example, I said:

Quote:

--- warm/cold/warm germinators: seeds that require warm conditioning, then cold condition, before they germinate in the 70F region.

Not exactly what I meant.  Peonies, for example, should be included in this group, but they actually begin germination in the first warm conditioning, and emerge above ground in the second warm conditioning.  So I believe the definition should read:
--- warm/cold/warm germinators: seeds that require warm conditioning, then cold condition, before they emerge in the ensuing warm conditioning.
In such a category, when actual germination begins is not stated.
I have edited my initial post to reflect this change.

Clear as mud?  Perhaps I've opened a can of worms here. :-\  I never claimed to be a "normal" person. ;D

Rick Rodich    zone 4a.    Annual precipitation ~24 inches
near Minneapolis, Minnesota, USA

Lori S.
Title: Moderator
Joined: 2009-10-27

RickR wrote:

Your initial remark made me wonder if you would then consider seeds that germinate at a simple 40F regime as "warm germinators", because the temperature was non-fluctuating.  

Uhh, no, I wasn't suggesting that. Perhaps my original statement is completely wrong, in any case (on top of being unclear and poorly worded  :rolleyes:).  ???

Lori
Calgary, Alberta, Canada - Zone 3
-30 C to +30 C (rarely!); elevation ~1130m; annual precipitation ~40 cm

cohan
cohan's picture
Title: Guest
Joined: 2011-02-03

I agree with the thought that it seems many warm germinators must be things that are able to germinate at warm with no other fuss, since that is convenient for so many modern gardeners germinating seeds indoors, which isn't the same as saying they need those temperatures--I think of all the natives and alpines that are 'easy warm germinators'- no way many of them get regular temps of 20C/70F until mid summer- here, not even guaranteed then., and never ever at night. The exact temps and durations that trigger germination must be varied, and probably not that important once you know the seed does not need conditioning- you either place them at room temperature or put them outside and wait for them to decide it's warm enough...

west central alberta, canada; just under 1000m; record temps:min -45C/-49F;max 34C/93F; http://picasaweb.google.ca/cactuscactus  http://urbanehillbillycanada.blogspot.com/

cohan
cohan's picture
Title: Guest
Joined: 2011-02-03

Maybe pertinent to this discussion- when I was reading (what little I could find) about germinating Salix (see the Seed starting chronicles thread), one study on S polaris and other arctic plants ( I forget if the study was on Svalbard) noted a much higher rate of germination at standard warm treatment (I forget if/what they said as the exact temp, but we'll assume around the usual 20C mark) compared to germination in the field at significantly lower temperatures, and also better than a slightly lower temp tested in the lab as well..

The point taken, I guess, is that 'warm' germinators may make do in nature with not so warm conditions, but that does not mean it is ideal...

I've found some confirmation of this myself- though unfortunately I haven't kept good notes- I've put a number of things outside in spring to germinate which are considered warm germinators, with mixed results. Note that our spring is not that warm, and not consistently. I'd thought, in nature they must be germinating in these up and down spring conditions, and if it's not warm enough they'll just wait till it is... Maybe so, but again, 'natural' germination rates may not be all that gratifying, nor even happen every year! Then again, some of those species may not germinate in spring at all, but rather in mid/late summer when seed is fresh and temps higher...

I think I'll have to bite the bullet and try to do more of my warm germinating indoors- which I haven't because space is very limited- mostly occupied with plants that  live indoors full time! I guess I could also wait till mid-summer (I have done that too) but once outdoor garden work starts, I find it hard to find time to get inside to do the sowing..

west central alberta, canada; just under 1000m; record temps:min -45C/-49F;max 34C/93F; http://picasaweb.google.ca/cactuscactus  http://urbanehillbillycanada.blogspot.com/

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