Hidden Springs Homestead may earn a commission for purchases made after clicking links on this page. Learn More.
Let’s talk about what soil temperatures for planting a garden are and why it is important. If you want your vegetable seeds to get off to a quick start, the soil needs to be warm enough for them to germinate or sprout.
It’s not a good feeling when you anxiously sow vegetable seeds in the ground and wait – but nothing happens.
So how do you know when is the right time to plant your garden seeds?
Soil Temperatures for Planting
Before you Plant – Know Your Frost Dates
Depending on where you’ll need to know this. Young seeds and transplants can be killed by frost.
Seed packets will give instructions on the backside that will say something like: Planting Instructions – …2 to 3 weeks prior to last frost…
To learn these dates in your area, pickyourown.org is easy to use by zip code. Or, if you prefer, contact your local extension office, and they can give you detailed information too.
But, even if you know your frost dates, you still need to keep in mind soil temperatures.
Why Is Soil Temperature Important?
Spring planting time is when soil temperatures are most critical. They are important in the fall and summer seasons too, but after a long winter, we are anxious to get into our gardens.
When is the right time to plant seeds or even transplants? Of course, this depends on what specific vegetable seeds or flowers, especially if you grow heirlooms, you are planting. Is it the right time to plant?
Fortunately, this information can be found on the back of most seed packets, as well as in seed company catalogs. And, of course, it can be found online as well.
Both seeds and transplants have optimum temperatures at which they will germinate or grow. If they are planted too soon, seeds may possibly rot, and transplants will do nothing but sit.
Or it can be right the opposite – if the soil is too warm, they most likely will germinate, but then the warmth of the summer season is too hot, and they don’t do well. So how would you know when the soil is warm enough for planting?
How To Measure Soil Temperature
This is not as complicated as you may think. It’s really very simple.
You’ll need to pick up a soil temperature thermometer. Or even a kitchen thermometer will work too.
Temperatures change daily with the low temps at night and then the sun during the day. So to get an accurate reading, you’ll want to measure 3-5 days in a row. Here’s how simple it is:
- Stick thermometer probe into garden soil – leave for 2-3 minutes. Take a reading and write it down.
- Next day – in another area, do the same and write it down; repeat for 3-5 days.
Now add all the temperatures together and divide by the number of days you took a reading. This gives you the average soil temperature.
Here’s mine this year: 42°+39°+45°= 126°/3= 42° I keep this in my garden journal each season. It’s a great way to gather soil temperature data and learn what worked or maybe failed.
NOTE: Raised garden beds warm more quickly than in-ground gardens. So if you have raised beds, you may be able to plant sooner. Keep this in mind for the type of garden beds you have.
RELATED: Even if you’ve never gardened before, this Vegetable Gardening for Beginners Ultimate Guide is for you! Learn everything you need to know from over 60 resources, all in one place, to be a successful gardener, including improving soil, cover crops, warm and cool season crops, organic amendments, fertilizing, watering, and so much more.
When to Plant Vegetables
Plant the following vegetables when the temperatures are:
Crops to Plant When Soil is: 40°-45°
- Lettuce – can be started indoors 4 weeks prior to the last frost and transplanted. It can be direct sown directly as well.
- Kale – is directly sown outside.
- Peas – These should be direct sown outdoors.
- Spinach – Direct sow spinach too.
- Carrots should be planted directly into the soil.
Crops to Plant at 50°-55°
- Onions are root vegetables, but they should be treated as leaf vegetables and protected from extreme temperatures.
- Leeks
- Turnips
- Swiss Chard
- Potatoes
Crops To Plant At 60°-65°
Warm Season – Soil Temperatures 70°+
Tips for Raising Soil Temperatures
As with any gardening, there are some tips you can do to raise soil temperatures to get a jump on spring gardening.
- Build raised beds – these warm sooner than in-ground gardens
- Cover the soil with black plastic. The sun’s solar rays warm the plastic, and the heat radiates into the soil.
- Use cold frames – again, the solar rays heat up the soil
- Use row covers
Take it from me since I failed miserably in my first couple of years of gardening. Investing in an inexpensive soil thermometer and taking a few trips out to measure the soil temperatures is worth the effort.
Our soil is normally warm enough to plant in later February to early March. When do you get to start planting spring vegetables?
Connect with Hidden Springs Homestead!
Be sure to follow me on social media so you never miss a post!
Dianne Hadorn is the owner of Hidden Springs Homestead, nestled in the hills of East Tennessee. A Master Gardener and lifelong homesteader, she teaches families how to grow real food, preserve it with confidence, and depend less on the grocery store. Through her practical, down-to-earth approach, Dianne has become a trusted source for beginners who want to build a sustainable lifestyle and fill their pantries with food they’ve grown themselves.
Thank you, great information. I still have a few weeks to plant also zone 7a.
Patricia, you are so welcome! If you have any questions, please feel free to message me. I’m glad to help.
This is such important information to know when you’re getting ready to plant! I think our frost dates are about the same here on the Oregon coast, and it really helps so much to cover the ground with black plastic in order to warm things up a bit before planting!
Hi Dianne, thank you for sharing this! It’s so good to know that successful gardening is about more than just knowing your last frost date. New info to me!
Oh Shawna, I’m so glad you found this helpful. I actually wrote it from experience hoping to help someone else not fail as I did my first year of gardening. It’s a big let down when you are a new gardener. Thanks for reading my post.
Luckily I live in St Lucia where we don’t have to worry about temperatures so much.
Monetta, Oh my, St Lucia. That is such a dreamy place for sure. Yes, your temperatures would be marvelous. I dream of visiting there someday. Thanks so much for reading my post. Merry Christmas!
Hi Dianne,
Where I live in Pa we are still actually just started winter so unless you have a green house or other way of inside growing there no much we can grow until April at least. I love how you explained the temperatures of the soil – that is very helpful. Have a healthy, happy & blessed Christmas and New Year.
Thank you Marla. I’m glad you found this article interesting. Trust me, I learned the hard way that seeds will not germinate in soil that is still too cool. Thank you for reading my post.
Hi, its interesting to read how its done in a area that is so much warmer then what I deal with, I might be shoveling snow off the area of the garden that I will be putting a hoop house over to warm the soil for a spot of early green growing at the same time you are planting LOL.
I do grow a number of things early that you are planting out but I have a much shorter amount of days so in order to get them to production, I need to start them earlier as my fall frost date will arrive before I know it.
I have a weather station on the farm so I know just what we have here for patterns 🙂
I am so with you on the different climates. We see snow on occasion but have met so many people like yourself that lives in a much colder climate and warms the soil. This is very interesting to me. We are blessed with a very long growing season I know.
I’m curious about your weather station. Honestly, I have never heard of this on an individual farm. I know that larger growers have them. I will be researching this to find out more. Very interesting. Thanks for reading my post.
If you grow anything outdoors you keep track of weather patterns and soil temperatures. Good to know what will take cooler soil and what has to wait for warmer weather.
It is very helpful I know. Actually, my first year of gardening, I planted way too early and my seed failed. I had no idea what I did wrong for a good while. Thanks for reading my post.