It’s spring! But is it time to plant your seeds? One of the most accurate ways to determine spring planting time is soil temperature – not air temperature, or even the calendar.
Early morning is the best time to monitor your soil’s temperature. The soil may warm later in the day, but you need to know the coldest temperature your seeds will experience. Planting seeds in soil that is too cold will prevent sprouting, and your seeds may rot.
How to Measure Soil Temperature
To take your soil’s temperature use a metal thermometer like one of these. Insert the thermometer into the soil approximately 3 – 4″ deep. Take the temperature for a few days in a row to be sure it is consistent, and before planting, check your weather forecast to be sure that a cold spell is not predicted.
Soil Temperature for Common Seeds
The following is the optimum temperature at which to plant some common seeds. Optimal means that 100% germination should be expected.
- Beans 80°F
- Beets 85°F
- Carrots 80°F
- Corn 95°F
- Lettuce 75°F
- Peas 75°F
- Tomato 85°F
Note that the optimum temperature may seem high. There is also an optimum range, or realistic temperature, which includes temperatures quite a bit lower. At the lower end of this range, one would expect 70 – 80 % germination.
Realistic temperatures for planting:
- Beans 70°F
- Beets 45°F
- Carrots 45°F
- Corn 70°F
- Lettuce 45°F
- Peas 45°F
- Tomato 70°F
Use the same guidelines for soil temperatures to plant seeds, and to transplant seedlings.
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To learn how to build a garden that builds healthy soil, be sure to check out my eBook The Art of Gardening: Building Your Soil. You really can become a better gardener, and you really can grow healthy, nourishing produce. It’s all about the soil! Click here to buy now.
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Easy Life Meal & Party Planning says
Stopping by from the Home Acre Hop to check out the soil temperatures! I was wanting this information the other day and lucky to run across it!
Marla says
Very interesting. You know I never actually knew that you were suppose to take the temperature of your soil, but it does make a lot of sense. Thanks for sharing on information. Visiting from The Home Acre Blog Hop. Have a healthy day!
Jennifer says
I have never taken the soil temperature. I did hear very many years ago that it is OK to plant outside when the birch leaves are the size of a squirrel’s ear. (OK, so you have to know how big a squirrel’s ear is!) I live in Alaska and that has really worked for me. Last year we had about a 2 week delay in warming up. This year we are about 2 weeks ahead of normal. I personally am about 2 weeks late in getting my seeds planted in flats though. Go figure. We have a beautiful birch tree outside our bedroom window, so I just keep my eye on it. It doesn’t look like it will be long until it is green. We had about 2 weeks of really warm weather for here. Last week it even hit above 70 one day. Now it is back down to the 40’s, but I can live with that. Happy planting. 🙂
Susan Vinskofski says
Fantastic! Yes, I’m sure that that is a fantastic way to determine time for planting!
Jenny says
Great info! Thank you for sharing this with us at the HomeAcre Hop!
everyone takes action says
When I initially commented I clicked the “Notify me when new comments are added” checkbox
and now each time a comment is added I get several e-mails with the
same comment. Is there any way you can remove people from that service?
Many thanks!
Susan Vinskofski says
At the bottom of each email should be a link to change your setting. 🙂
Darcie says
Thank you for all your great wisdom! Sometimes, I just look for “volunteers”. For example, it looks like borage has sprouted this year, so maybe other plants with similar needs can be started. I wonder if you’ve stumbled upon any resources for this or for the temperature requirements for many different types of plants? I’ll definitely use your chart to help!
Susan Vinskofski says
I really like the way you think. I just googled “soil temperature for borage to sprout” and I find that it is 70°F. So, I think if you googled individual plants to see when they sprout, you could come up with a great list! But not knowing soil temperature you could also make a list that says “when borage spouts, x, y, and z also come up”. I know that there is a bit of info like that out there. For example, look for morels when the lilac is in bloom. Thanks so much for stopping in and sharing with us!
vivian gerard says
what do i do if the temperature goes down
Susan Vinskofski says
If your seed / seedling is already planted, there is not a lot you can do except to protect the plant if frost occurs.