Thursday, March 26, 2009

Vegetable seed germination temperatures

I ran across a great chart recently illustrating the difference in practical planting times and optimal planting times for vegetables.

Vegetables are quite domesticated, needless to say, and far from their native origins. They've been selected for rapid and uniform germination (among other traits such as big leaves or large tasty fruits).

But the interaction between soil temperature and seed germination is fascinating. Many of our warm season crops will germinate rapidly and uniformly at temperatures that most of our soils will never achieve, even in a warm climate like ours (in the Southeastern U.S.). But germination will occur, more slowly, at lower soil temperatures and this is what this chart illustrates so nicely.


It was included in a Gardener's Tip about When is it warm enough to plant? from the Gardener's Supply Company, an informative online/catalog retailer based in Vermont with lots of great information on their website.

6 comments:

  1. Thanks for posting this. I'm trying to figure out the best temperature for starting my seedlings inside so I put them on my warm DVR. I was afraid they were too hot since they regularly get up to 85 degrees. Now I know that it is optimal for many of my seeds.

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  2. Very interesting. This still leaves me puzzled as to why my spinach germinated so much more slowly than my carrots (notoriously slow!) and beets, all planted on the same day in the same garden area. The "practical" germination temp is the same for all, but the optimal temp for spinach is lower. One would think... Oh well, guess that spinach had its own reasons. Think I'll get a soil thermometer.

    And this reminds me that I'd better get my squash seedlings going asap. In my still slightly "impractical" conditions in a cool garage, even under a light and over a heat mat, it's going to take them awhile. (Feline interference prevents seed starting indoors at our house.) My eggplants, started two weeks ago, are just peeping up.

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  3. Thanks for sharing our chart with your readers. We love when bloggers help spread the word.

    Would you mind adding a link to the article
    http://www.gardeners.com/When-is-it-Warm-Enough-to-Plant/9029,default,pg.html

    or to www.gardeners.com ? We would really appreciate it.

    Great blog too! Thanks, Joe @ Gardener's Supply

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  4. I think spinach is temperamental -- short-lived seed, higher temperatures decrease germination, poor handling (heat) can kill seeds, etc. etc.

    I've had the best experience with ultra-fresh seed (this season with Indian Summer spinach seed from Cook's Garden) -- it's germinated fabulously. But, I've had plenty of failures, too, before I learned about how short-lived the seed was!

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  5. Joe-
    Happy to add another couple of links to your content. Loved that seed chart!
    Lisa

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  6. That's it,most likely-- the spinach seed are old and we had that warm spell just after they were planted. Happily, enough managed to come up in their own sweet time. It's a great variety from Rene's Garden Seed, "Oriental Giant"-- very large leaves but sweet and tender and quite prolific (once they germinate).
    Thanks, always assumed spinach seed were viable as long as lettuces can be (of course, it's a different family-- should have known).

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Please share your thoughts with me. I always enjoy hearing from fellow gardeners and nature observers of all sorts, as well as whomever else drops by.

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