The Soil Temperatures You Need for Seeds to Germinate

seed trays in the green house

Unless your dirt is the right temperature, your seeds will never germinate.  You can use a basic meat thermometer you don’t mind sacrificing to the cause (because once you stick it in the dirt, odds are pretty good you won’t want to stick it in your pork!)

The danger of planting seeds prematurely is that they will just sit and ROT before they ever sprout!  (Also, it seems to me the longer I have seeds sitting just below the soil, the longer rain has to wash them away and the longer the birds have to find them all.)

There are a couple things you can do to side step Mother Nature if she’s being a bit cold.

  • Start seeds indoors or in a greenhouse.  A heating mat is great for helping things along, I’ve heard.  I don’t own one yet….but I want!
  • Plant early spring crops in large pots- the dirt warms up faster
  • Use raised beds.  This is a good idea anyway, to help with drainage or to act as a quick fix for less than ideal soil.  Like the pots, the soil will warm up faster above ground
These temperatures were taken from heirloomseeds.com to give you an idea of what you need before your seeds will sprout, and how long it will take.  (They also sell soil thermometers there, for a pretty good price it seems, if you want something quicker and more suited to the task!)
VARIETY OPTIMUM SOIL TEMPERATURE FOR GERMINATION DAYS TO GERMINATE AT OPTIMUM SOIL TEMPERATURE
 Bean, lima  85 degrees F  7 to 10 days
 Bean, snap  75 to 80 degrees F  7 days
 Beet  75 degrees F  7 to 14 days
 Broccoli  65 to 75 degrees F  5 to 10 days
 Brussels sprout  68 to 75 degrees F  5 to 10 days
 Cabbage  68 to 75 degrees F  5 to 10 days
 Cantaloupe  80 to 85 degrees F  5 to 10 days
 Carrot  75 degrees F  12 to 15 days
 Cauliflower  65 to 75 degrees F  5 to 10 days
 Celery  70 to 75 degrees F  10 to 14 days
 Collard  70 to 75 degrees F  5 to 10 days
 Corn  75 to 85 degrees F  7-10 days
 Cucumber  70 to 85 degrees F  7 to 10 days
 Eggplant  75 to 85 degrees F  10 to 12 days
 Endive  70 to 75 degrees F  10 to 14 days
 Kale  70 to 75 degrees F  5 to 10 days
 Kohlrabi  70 to 75 degrees F  5 to 10 days
 Lettuce  65 to 70 degrees F  7 to 10 days
 Melon  80 to 85 degrees F  5 to 10 days
 Mustard Greens  70 degrees F  5 to 10 days
 Okra  80 to 85 degrees F 7 to 14 days
 Onion, bulbing  70 to 75 degrees F  10 to 14 days
 Onion, bunching  60 to 70 degrees F  10 to 14 days
 Parsnip 70 degrees F  14 to 21 days
 Pea  65 to 70 degrees F  7 to 14 days
 Pepper  78 to 85 degrees F  10 to 14 days
 Pumpkin  70 to 75 degrees F  7 to 10 days
 Radish  65 to 70 degrees F  5 to 7 days
 Rutabaga  65 to 70 degrees F  7 to 15 days
 Spinach  70 degrees F   7 to 14 days
 Spinach, New Zealand  75 degrees F  10 to 15 days
 Squash, Summer  75 to 85 degrees F  7 to 14 days
 Squash, Winter  75 to 80 degrees F  7 to 14 days
 Swiss Chard  70 to 75 degrees F  7 to 14 days
 Tomato  75 to 80 degrees F  7 to 14 days
 Turnip  65 to 70 degrees F  7 to 14 days
 Watermelon  75 to 85 degrees F  7 to 14 days
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5 Responses

  1. Seeee….. I’m quite convinced that radishes and peas germinate at much much lower temp than that. But yeah, I’m pretty sure my cucumber seeds are rotting 🙂

    The green house looks great!!!

  2. Thanks Myrnie, great chart, thanks for sharing!

  3. I use mats and have really good luck with everything except the blasted cole crops, but I so want a racking system. Or a greenhouse. Squee!

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