Will my okra seeds germinate with fluctuating soil temps?

DrHorticulture_(Z3 Central Saskatchewan)May 11, 2009

I have them direct sown under polytunnels. Soil temperatures range from 90-95 in the day to 45-50 at night. Will it germinate well despite the cool nights?

I have some transplants indoors as backups.

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digdirt2(6b-7a No.Cent. AR HZ8 Sun-35)

Wow! That is some drastic soil temp changes. Air, sure but it's very strange for soil to cool off that quickly. Will they germinate with those sharp changes I honestly can't say but it sure isn't the ideal soil temp so I'd sure keep the inside backups going.

Okra is such a summer-lover crop. If you wait until late June or July to plant it as we do down here would you have time to get a crop before fall freezes?

Dave

    Bookmark   May 11, 2009 at 7:35PM
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anney(Georgia 8)

DH

I suspect they'll have a hard time germinating with such low night temps, even if it's warmer because of the tunnels.

What's important are soil temps, not ambient temps. Soil temps fluctuate far less than ambient temps. You can test it with an ordinary oven probe thermometer.

My notes say they'll germinate in 10-14 days with soil temps at 80-90 degrees. I haven't planted them here yet because the soil isn't that warm. Cooler soil temps take longer, and at some cool temps they won't germinate at all. Somewhat warmer temps cause quicker germination.

But every time I've looked at this kind of data on various sites, the soil temps are never exactly the same. Most give minimum, average, and highest soil temps needed for germination. If you get in the ballpark you'll be okay.

Here is a link that might be useful: Soil temps for seed germination

    Bookmark   May 11, 2009 at 7:41PM
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anney(Georgia 8)

I misread. I thought you listed ambient temps, not soil temps. Like Dave, I can't IMAGINE soil temps fluctuating that wildly, but maybe they do! Could you say why?

    Bookmark   May 11, 2009 at 7:44PM
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DrHorticulture_(Z3 Central Saskatchewan)

Hi, thanks for the quick replies. The nights are still very cold (close to freezing) but as it's supposed to warm up next week, I thought I would take a chance. I only have a single layer of poly, so that's probably why it gets very steamy during the day and cools off rapidly at night. The soil temps outside are in the upper 30s/low 40s during the night. I'm probably crazy to attempt okra this early in my zone but I wanted to see if it could be done. I have very little interest in vegetables that would actually grow well in my zone...

    Bookmark   May 11, 2009 at 7:51PM
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DrHorticulture_(Z3 Central Saskatchewan)

PS: I forgot to mention that my soil thermometer is only an inch deep, at about the depth of the seed.

    Bookmark   May 11, 2009 at 7:56PM
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namfon

I have not heard of a soil thermometer that short.

I always thought you should take soil temps at 3 ~ 5 inches deep which is closer to the root zone.

My soil temps only fluctuated about 10 - 15F this month
( 60 - 75F )when the outside temps fluctuated between 40 - 80F. Before I layed the clear plastic down to heat it up the soil temp was 44F. If you have the plastic weighted down well and take the temp a bit deeper you may find it warmer.

Also agree with Dave that you should have enough time to mature Okra if you planted later. If you try it I'd like to read about your results.

hth

    Bookmark   May 12, 2009 at 3:56PM
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jnfr(z5b CO)

I started some okra seeds indoors in peat pots and they popped up pretty fast. I won't set them out till nights are at least 60 though.

    Bookmark   May 12, 2009 at 4:09PM
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lantanascape(z6 Idaho)

FWIW, I'm trying starting my okra by soaking the seed for the first time this year. I wrapped the seed in a wet paper towel and put it in a ziploc bag and got 100% germination at room temperature within 4 days. I popped the seeds with the emerging radicle into seed starting mixture in a flat a few days ago, and hope they emerge soon.

    Bookmark   May 12, 2009 at 4:58PM
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DrHorticulture_(Z3 Central Saskatchewan)

Thought I'd post an update on the okra. I think the soil was just too cold in the first few days when I put the plastic on, but eventually the lower layers warmed up. I have about 50% germination so far, so I'm hoping that the rest come up too. But the weeds!!! They love it in there. The only good thing is that the steam bath environment has shifted the weed population away from dandelions to redroot pigweed, which is easier to pull out.

    Bookmark   May 30, 2009 at 4:03PM
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jimster(z7a MA)

Linked below is another source for germination temperatures.

Temperature at seed depth fluctuates over a great range, depending mostly on radiant heat from the sun, or lack of it. Yesterday was cloudy and the soil at 1 1/2", the depth of my corn seeds, was 58°F. Today was sunny and the temperature at that depth was 94°F.

I'm sure the rate of germination is affected by fluctuations in temperature. However, predicting the result is merely guesswork based on interpolation of the figures in those charts. At a constant 58°F my corn should germinate in 12 days. At a constant 94°F it should take 3 days. Obviously, the actual time will be somewhere in between. Any guesses?

Jim

Here is a link that might be useful: Germination Temperatures

    Bookmark   May 30, 2009 at 7:17PM
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