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njbiology

For experts in cold-stratification -- native seeds.

njbiology
9 years ago

5 sets of questions regarding cold-stratification of seeds...

1. I began cold-stratification (moist peat, refrigerator) for most species that I have (dozens). Some of these species only require 30 days of stratification, and others require approx. 20 days. The only species that I did not began stratification for were the legume -- and that will be covered in my next question. So, for seeds requiring only 30 days (for instance Callirhoe spp.), will they germinate far too early? They were started on December 23... does that mean they will wake up from stratification in February or March, even though refrigerated? IF this is a risk, can I take any species out of the refrigerator and leave the individual moist peatmoss/seed filled bags open so that they dry out and then begin the process of stratification 30 days before spring? Or is it just that they NEED 30 days for a decent % of germination, but would benefit from the 90 days that I could give them in refrigeration?

2. For Agrostis spp. Surprisingly, members of this genus is listed as requiring 60 days of cold stratification. If this is so, same as with my first question. I feel that grasses -- especially those that do not require cold stratification (Soghastrum, etc.) -- will wake up in the refrigerator if given too long. I think that I'm taking a big risk by starting them now. The problem with taking them out of the refrigerator now is that if they do not absolutely require cold-stratification, they might wake up while I'm trying to dry the bags out for later starting the cold-stratificaiton process. I should have contacted you before starting all this, but hopefully you will let me know its ok to give seeds longer. Another idea would be to take the seeds out and direct sow them. I preferred to do things indoors because I have a seed bed (weed seed free soil) prepared so that when they are at the brink of germination, I could sow them and manage the bed for a year prior to transplanting.

3. For Phlox pilosa and other difficult-to-germinate (C) code species... can I place the moist bags in the freezer for two weeks, then the refrigerator? I read a research paper which indicated success with freezing -- but I don't recall whether the seed much be dry if freezing, and then moisture is added. P. pilosa shouldn't be allow to dry out, so I'm not sure. Also, I have a little bit of GA-3. Should I sprinkle a pinch into each bag of difficult-to-germinate seeds at the very end of the stratification period. I might even sprinkle some wood ash for tricky prairie species. I

4. Are high-PH species are best cold-stratified in clay rather than in peatmoss? Wood ash may help in such cases.

5. Although native the legumes are listed as requiring just 10 days of cold-stratification (cf: PM Nursery, etc.), the seed (various species) I received have not been scarified. Do you recommend that I wait until the very end of spring to begin cold stratification (with use of the species-appropriate inocula)? Or, because they have not been scarified, should I begin stratification at this time and in a few months (end of winter), add the inocula? The only species I haven't begun stratification for were the legumes because I could see 60 or 30 being stretched out to 90, but not 10 days.... unless not using the incolum for a species until the end will ensure the stretch is achieved. I'm just concerned that 10 days is not enough since they haven't been scarified.

Thanks!

Hopefully many will benefit from responses to these 5 questions.

Comments (8)

  • morz8 - Washington Coast
    9 years ago
    last modified: 9 years ago

    Lots of questions, I do have a couple of thoughts...

    Once you have wet the seeds and moisture has breached the seed coat, you cannot let them dry out again. The embryo will die.

    Dry storage in a freezer is just storage, it doesn't help to break dormancy. I haven't found many cases where freezing seeds once moist is helpful, most of the time it just puts things on hold until the temp is not quite so cold - for most plants seeds, 35-40F is plenty cold enough to stratify. Taking a seed that has been in moist medium, and plunging it abruptly from room temperature into a freezer at 0-10F may be damaging to some too - the embryo may be shattered and seed killed.

    Some seeds will germinate in a refrigerators temperatures, others will not until brought back into someplace warmer. I can't speak for callirhoe ssp, but Callirhoe involucrata for example will germinate at 40F although it can take many months and not all c. involucrata sown will germinate at the same time, they may be many days or even weeks apart.

    I don't think that phlox pilosa is said to be difficult to germinate as much as it has short viability and it can be hard to acquire seed fresh enough to meet your needs. In that case, GA3 wouldn't be particularly helpful, and, it's not helpful for all seeds. The reverse is true, it may even damage seeds from particular plants, there are but a few times most of us would use it.

    In a Z7, had you thought about moving some of those pots outdoors and exposing them to natures fluctuating temperatures. I have several things I'll be sowing and placing outside over the next two months, exposed to rain, frosts and weather, protected (chicken wire) from sparrows and chipmunks.

    I don't know that I would recognize 'the brink of germination'. Seeds that have germinated indoors, need to be grown indoors until the seedlings can be acclimated to being outside over a period of time. Wind, temps, natural light will be too hard for them all at once.

    This post was edited by morz8 on Sat, Dec 27, 14 at 1:41

  • morz8 - Washington Coast
    9 years ago
    last modified: 9 years ago

    jebfarm, do you ever check your methods against the Clothiers database (seems to be more often for commercially acquired seed), or the book Making More Plants by Druse (seeds here more freshly obtained)?

    Eremurus and hellebores both described as warm, cold, cool germinators there and you're right, it has to be the right sequence and not out of order. I've raised many hellebores, try to sow no later than Sept and I leave the pots outside to find germination in late winter my cool Z8. That last stage, cool, is very difficult for me to achieve indoors, I don't have a room cool enough.

    Here is a link that might be useful: Clothiers database

  • jebfarm
    9 years ago
    last modified: 9 years ago

    I do check with Clothier's data on seed germination, it is helpful. A method that I came up with myself and use for germinating seed of prairie wiildflowers and grasses is to cover the seed once it is sown with a coarser perlite rather than a peat based germ mix which seems to smother the seed. This method is used for seed that requires a covering, some seeds need to remain uncovered and exposed to light for germination. I found that Sporobolus heterolepis (Prairie Dropseed) doesn't germinate at all when lightly covered with a peat based media - I got a few to germ that were left uncovered but I get high germ when the seed is lightly and evenly covered with perlite after it is sown. This tells me that prairie species need more gas exchange or exposure to the air while at the same time being covered so the seed is protected and does not dry out.
    I wouldn't worry too much about your seed germinating early in the fridge, I have Dictamnus albus and eryngium sprouting now in the seed trays that are in my refrigerator - the mice kept getting them in my garage - the cold temps will keep them from growing much and they will be taken out of the fridge in late March or early April to go out into a cold greenhouse to continue growing.
    Keep in mind that seed that requires stratification for germination can not be hurried along with warm temps! We aren't growing marigolds or petunias here. If you see no activity after you might expect to see signs of life, keep the seed colder longer rather than warming them up - most seeds will start to sprout while still chilled and germ best while at cool temperatures. Again, good luck!
    I wanted to add that some varieties that require stratification do only start to 'wake up' and grow once the temps warm up, like morz8 said - but not too warm - temps in the low 60's are better than say mid 70 or 80 degrees. Try to avoid quick extremes and no need for additives like wood ash or innoculants for germination - I've never used GA-3 myself and don't really see a need for it. There is no secret incantation or method that will make this process go much faster, it is one of those things that takes time. 'Tricky' things - violet species for example - germinate for me better when they are placed in a coldframe outside because the rain and snow are washing out the germination inhibitors that keep the seed from growing at the wrong time. That is my educated guess.
    I remember that when I grew Callirhoe involucrata from seed the germination was very erratic, seedlings slowly germinating in an outdoor seed bed for more than three years!

    This post was edited by jebfarm on Sun, Dec 28, 14 at 13:58

  • njbiology
    Original Author
    9 years ago
    last modified: 9 years ago

    Thank you very much, jebfarm & morz.

    1. Should I worry about the times that I remove the stratified seeds from the refrigerator which is perhaps 35F and then bring the bags containing the seeds out of the refrigerator into room temperature (perhaps 80F)? Then I put the bags back into the refrigerator.

    2. As for pots outdoors, I don't have them in pots but have them in individual bags. The idea is to begin stratification in the refrigerator for a few weeks and then in January, on a warm day, sow the seeds (that are in medium) outside in a seed bed that I am working on completing. ion temporarily.
    3. Maybe clay (kitty litter) would be better for prarie dropseed, rather than a covering of peat.
    4. Last year, when seeds germinated early they got leggy root growth and died out. Maybe I needed to put some fertilizer to hold them off a little while longer?
    5. No need for inoculum for legumes to aid in germination? The seed is not scarified. How long will it take for most legumes to stratify properly?
    Thanks,
    Steve

  • docmom_gw
    9 years ago
    last modified: 9 years ago

    I strongly recommend wintersowing. Morz8 suggested planting your seeds in pots and placing them outside, though protecting them from animals, etc. That is almost exactly what wintersowing entails, though use of semi-enclosed containers provides more greenhouse effect and more consistent moisture levels.

    Martha

  • jebfarm
    9 years ago
    last modified: 9 years ago

    Steve - no, no, no, and no, DON'T bring your seed out into 80 degrees from being in the fridge, DO NOT put kitty litter on anything, DO NOT FERTILIZE young seedlings, especially if stretched out! The reason they are weak is because they aren't being given enough light, or the soil is being kept too moist or the temperatures that you are growing them on is too warm - or a combination of these things - your seedlings are not stretching from lack of fertilizer. And no, somehow it is a misconception to put innoculant in with seeds to aid germination!!!!!!! That is best used for peas or beans that are planted out in the field. It is used for the root systems of legumes to enhance colonizing bacteria that produce nitrogen (which they are able to do on their own, to me it isn't something that is required.) Again, DO NOT DO ANYTHING UNUSUAL TO YOUR SEEDS! Don't try to force the germination and growing to fit your schedule - nature always wins in the end.
    As Martha said above since you appear to be so new to this, it would be best - I am sure of this - to simply sow ALL of your seeds outdoors in a ground bed and let mother nature take care of getting your seeds to grow and mature. I have read a few of your older posts, and you are so caught up with the technicalities of growing plants that it is interfering with you using sound techniques that actually work - again good luck!

    This post was edited by jebfarm on Tue, Dec 30, 14 at 10:48

  • njbiology
    Original Author
    9 years ago
    last modified: 9 years ago

    1. I will DEFINITELY sow the seeds outdoors now that you guys let me know all of this. BUT... is it too late? After refrigerator stratifying my cold-stratification requiring seeds (while I'm completing my seed frame.. just need soil to be available from homedepot/lowes), I then learned that some of the seeds are rated for 30 days of stratification, and others for 60 days. My concern is that since I started them on December 23, the ones requiring 30 days and many of the ones requiring 60 days will sprout well before April. I only intended to start the germination process in the refrigerator, with the greater intention of soon sowing them outdoors on a warmer winter day upcoming -- maybe in a week or two. So, since they will be in serious winter conditions, I doubt that the ones rated for 30 or 60 will sprout early. I guess its 30 days in a refrigerator, which is not really freezing, but all winter long if sown outdoors. I just wish that I only started the 90-day requiring ones in doors, and left the 30s/60s for when I finished the seed beds (in a week or so, when soil becomes available... need 24 two-cubit foot bags of composted soil.)

    2. Early on in the stratification process, I removed the seeds from the refrigerator (maybe 34 F) and left the bags out in room temperature (maybe 80 F)... then put them back in the refrigerator. Did I destroy the embryos? I would think I would if it was the freezer to room temperature. In the past... last year, I moved seeds from a refrigerator (maybe 36 F) to room temperature (maybe 78 F) and many species did fine.

    These seeds are going outside as soon as I get enough soil to cover the area they will be caste upon... and stepped over, not buried in most situations.

    Thank you very much in advance..

    Steve, Zone 7a