How to use Gibberllic Acid-3 on seeds? Too late to cold-stratify?

njbiologyJanuary 20, 2014


I live in NJ (USDA zone 7a/6b), and purchased native wildflower seeds of 45 locally occurring species of wildflowers -- most of which require cold-stratification; however, the seed was collected from plants in a slightly colder region, and therefore accustomed to a slightly longer cold-stratification period.

If I sow the seeds on January 23, will there be enough of a cold/thaw period for at least some of the seed of these 45 species to germinate this upcoming growing season?

Perhaps I missed the window-of-opportunity. I hope that the seed that doesn't germinate will remain viable in the ground until next year, if so..

I ordered some Gibberllic Acid-3. Can someone hear advice me (and everyone else interested) as to how I can properly utilize the acid in assuring that most of the seed does germinate this year?

Thank you!

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I can't answer your question on the use of Gibberllic Acid-3, as I've never tried it. Elsewhere I have read that GA-3 can help some types of plants to germinate better and faster, but in other types of plants some people said it made no difference.

Regarding stratification times: This depends on exactly what type of wildflowers you are trying to grow. If you know specifically which kind you have you can look at Tom Clothier's germination database and determine the stratification times. If you do not know what you have then it's hard to give accurate advice.

I grow mostly trees and shrubs from seed and most of them take between 30 and 90 days of cold stratification before germination.


Here is a link that might be useful: Tom Clothier's germination database

    Bookmark   January 20, 2014 at 7:53AM
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Thanks for the reply!

Most of my seeds require 3 months of stratification, according to the consensus.

For seeds that don't require 3 months of warmth before 3 moths of cold; that only require 3 month of cold-stratification:

Rather than sowing them directly outdoors (which would mean that they wouldn't receive enough stratification), might I want to keep them in moist sand in the refrigerator (from the end of January through the end of April), and then sow them during the first week of May?

If so, maybe I should put them in the refrigerator and freezer, back-and-forth.. to simulate freezing and thawing?

Or will the Gibberlic Acid-3 treatment followed by sowing outdoors work out well for me?

In some situations, as with Lilium superbum, the seed requires 3 months warm followed by 3 months cold.. maybe the GA-3 will overcome this as well?


    Bookmark   January 20, 2014 at 9:29PM
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morz8(Washington Coast Z8b)

Couple of flaws in your plans here - First, GA3 isn't helpful for all seeds and in some cases can be harmful. You may have to research each specific seed you've purchased and see if the acid has been tried, if there is documentation available that would help you to decide which its appropriate for, where it hasn't helped, and keep in mind it isn't just help or not help but has the potential to damage seed.

Few seeds need to actually freeze and are only 'on hold' when frozen, extending the conditioning process until temps are not quite so cold. 35-40 is cold enough for the moist chill. The abrupt plunge from refrigerator to freezer instead of the gradual drop over many hours as would happen outdoors can kill seeds, shatter the embryo. Fluctuating temps can be helpful in stratifying seeds, but not 40 to 0 in the span of a few seconds.

    Bookmark   January 21, 2014 at 11:33AM
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digdirt2(6b-7a No.Cent. AR HZ8 Sun-35)

Sorry but I think you are way over-complicating the process, over-thinking it.

First the vast majority of seeds, assuming they are relatively fresh, will germinate just fine without any GA. And yes, given the unusual colder weather in your region this year, planting them now will allow for adequate stratification. Even in a normal year it is sufficient stratification. Would it have been better to plant them a couple of weeks ago? Sure. But it doesn't make that much difference to them.

Keep in mind that these are wildflowers not some rare hothouse type plant. And that they are well-adapted rather than some foreign plant trying to grow in a foreign environment. As such they are survival-tough and very tolerant of less than ideal conditions.

And I agree that for the good of the seeds you do NOT want to do the freezer then fridge approach you describe.


    Bookmark   January 21, 2014 at 12:30PM
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@Morz8 and Dave (digdirt): Thank you -- this is, of course, very helpful... no freezing them.

I think what I will do it sow 50% of each species now, and the other 50%: place in zip lock bags with vermiculite that has been moistened; leave at room temperature for 24 hours and then refrigerate until the first week of May; then sow.

For the very few species that require a period of warm-stratification followed by a 3 month period of cold-stratification, I will keep in vermiculite for 2 months at room temp, then put in refrigerator for 3 months, then sow indoors and grow them in a green house for a year.

Since I have a very small amount of GA-3.. enough to treat just a few ounces -- whereas I have 3.5 pounds of seed, would it be a bad idea to add this comparatively small and therefore dilute amount to the vermiculite so that there is a trace amount of GA-3 during the process of stratification. i.e. since I have it, since it will be a minimal amount, etc.?


    Bookmark   January 22, 2014 at 2:55PM
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digdirt2(6b-7a No.Cent. AR HZ8 Sun-35)

would it be a bad idea to add this comparatively small and therefore dilute amount to the vermiculite so that there is a trace amount of GA-3 during the process of stratification.

It probably wouldn't hurt much of anything given the extreme dilution but personally I'd save it for use on something where it is really needed. It isn't cheap stuff. :)


    Bookmark   January 23, 2014 at 4:57PM
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DavidLMO(5 B)

WRT GA-3 - study up before you start horsing around with it. Read Deno material and check out germination and GA-3 on the Hudson site.

When you say you have a small amount - what amount? Dosages of GA-3 are measured in Milligrams and 500 PPM is one of the most common dilutions. The amount that can be placed on a toothpick head is the amount that we are talking about in terms of measurements.

Just willy-nilly tossing some GA-3 into a bunch of seed cause you have it is rather foolish. You might kill or drastically deform the seeds.

Just a word of warning.

    Bookmark   March 27, 2014 at 11:07PM
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