Growing edible perennials in the north is so valuable! Even though I am starting all kinds of food crop seeds inside while there’s still snow outside, the first crops I harvest always end up being our early spring perennials. Plus spring perennials play well with other early spring annuals like salads and radishes.
It can feel like a superpower to be eating from your land as early as May, especially when all you did was rake back a few leaves…
Why Grow Edible Perennials in Cold Climates?
We have an extremely short growing season in Minnesota, under 150 days! So we need plants that can take the freezing cold and then warm up fast, and early spring perennials make it happen.
Understanding soil temperatures, rather than just the calendar dates, allows gardeners to get planting earlier by matching seeds to ideal soil temperatures for seed germination. Especially with local unpredictable spring air temperatures this can make or break a garden season.
Let’s dig into soil temperatures for early season success.
Climate Change in the Garden
While specific years will always fluctuate, the country and Northern world is experiencing a long-term trend of warming winters. Minnesota’s average annual temperatures have increased by 3.2°F between 1895 and 2024.
Spring soil temperatures in Minnesota show significant year-over-year variability, heavily influenced by snow cover, spring precipitation, and air temperature, with a long-term trend toward earlier warming. Minnesota is recording earlier spring soil warming temperatures overall.
In recent years, soil temperatures have varied from early-season warm spells to late-season “nosedives,” with 4-inch deep soil temperatures commonly reaching 50°F in April. But we still get anomalies like April readings of 33°F in 2014 and 60°F in 2012.
How to Measure Soil Temperature for Seed Germination
This spring in my Minnesota garden in mid-May I still had soil temps dip down below 50°F in the early morning, and we’re still having frosts this May. In recent years this temperature was higher.
Planting in protected growing areas like Low Tunnels or a Cattle Panel Greenhouse can increase soil temperatures by 10–15°F compared to open ground, promoting faster, healthier growth. These consistent few degrees warmer means so much for good germination early in the season.
Use a simple soil thermometer (I actually have a few of them) and test roughly 4-6 inches deep to get my readings.
To know the low temperature you have to check it before the sun starts warming it for the day.
Leave the thermometer in the soil for at least 5 minutes before reading so it can level off
Each seed has its own ‘happy place’ temperature range. And trying to push the season by planting out a seed before the soil is warm enough means that seed will likely rot in place. So be patient for your soil to warm up, or help them along with covering.
Seed Germination Temperature Chart
Minimum Soil Temperatures for Germination
Beans – 60°F
Beets – 40°F
Broccoli + Cauliflower – 45°F
Cabbages – 55°F
Carrots – 45°F
Corn – 55°F
Cucumbers – 65°F
Lettuce (most greens) – 40°F
Melons – 70°F
Onions – 40°F
Peas – 40°F
Peppers – 65°F
Tomatoes – 60°F
Spinach – 35°F
Squash/Zucchini – 70°F
Direct Sowing Versus Starting Indoors
This above graph information combined with which plants to direct sow versus which to start indoors can help you get your garden rolling as early as possible- giving many more harvests throughout the seasons.
It also means I can stagger my planting times, so beans will be going into the soil in about a week, while radishes and spinach were direct sown weeks ago.
Depth matters – deeper soils hold warming easier, shallow (over rock) cool quicker. The amount of sand and how damp the soil is overall also has a real impact. In general soil still warms and cools the most in the first inch.
While damp soil holds more heat than dry soil, evaporation of that excess moisture consumes heat which is a cooling process. Avoid bone dry soils AND oversaturated soil for optimal warming of non-covered soils in spring.
It also matters how deep you’re planting that seed. Smaller seeds like lettuce and carrots usually are planted closer to the surface, which is warmer than 6” down. But can also cool off more. But this cooling is easily moderated by adding a layer of fleece or plastic row cover to the seeds.
For more information on Starting Seeds Read THIS ARTICLE
Soil Temperature FAQ:
What temperature do seeds germinate at?
Seeds vary widely in their preferred germination temperature range. From soil temperatures starting at just above freezing at 35°F to 75°F depending on where the seed naturally developed. So when northern gardeners want to grow warm weather crops, we need to trick seeds into germinating by raising temps inside.
Can I use a Meat Thermometer to Measure Soil Temperature?
While you can use a meat thermometer to measure temperatures, it is best to use a tool meant for outside if you plan on keeping it outside. The soil thermometers also have a different range of temperatures and larger font.
Does soil temperature matter more than air temperature?
Short answer is Yes, but really, it depends… In general, seeds know what the soil temperature should be to germinate, remember they only have one shot. They are not reading the air temperature because they are in the soil.
But (there’s always a but), if you’re raising the soil temperatures by growing undercover you need to be more aware of late spring cold snaps that can kill off above ground plant greens. But if you start with the cool weather crops, you should be safe.
Air temperatures do matter, and most states gather this data and make it available online. In Minnesota our DNR hosts an interactive map with frost and freeze date probabilities that I find invaluable.
All of this is to say…
Know what your soil temperature is. Know what temperature your specific seed prefers.
You’ll have better germination, less plant stress and a happier overall gardening experience…
A recipe with two ingredients a little time in the dehydrator with a big pay off: rhubarb sour candy from the garden!
These taste like if Sour Patch® had a kid with simple ingredients + kept the fiber. I like the big flavor coupled with the little chew. I get to help out at our local elementary school, and the kids go crazy for them every year!
It is a great, simple way to use up some of the rhubarb and not make yet another crisp… but if you’re looking for tips on growing rhubarb or other recipes, I have you covered.
Rhubarb Sour Candy Recipe
Ingredients:
4-5 stalks of Rhubarb
1 cup sugar
1 cup water
Directions: Slice the rhubarb lengthwise on a mandolin (I use my thin setting) leaving them as long as you can. This is the putzy part, and I usually save the extras pieces that don’t make nice long strips for making rhubarb sauce or something.
Mix a 1:1 sugar/water solution into a medium sized sauce pan so the rhubarb slices fits easily.
Simmer for 3-5 minutes or until you notice the stalk strips becoming much softer. Then, using a pair of tongs, gently pull out the strips and lay flat on either a dehydrator tray or parchment paper.
Set dehydrator to 140F and let them go for 7-8 hours, or set your oven at the lowest setting (usually 225F) and watch closely after 15 minutes. Remove from dehydrator or oven and let cool completely.
Chop into desired sizes, and store in airtight container for up to 1 week. (But they will be gone before that!)
Let me know if you try this fun “nature’s own” rhubarb sour candy recipe and what you think of it!
Let’s shrink your lawn with sustainable turf alternatives!
This guest post is brought to us by the legend, Bob Dahm. Many of my Midwest garden friends will know him as “Organic Bob,” which is how I knew him when we first met about 5 years ago.
He has guided our family on our own home lawn re-seeding (with tougher native grasses) and bee lawn areas with great success. This is because he sees our yards and gardens as integral parts of the natural world, not separate from them.
Are you itching to get planting but the soil isn’t warming fast enough?
Growing under the cover of a low tunnel is the answer to jump start your spring vegetable garden. Most of the veggies shown here were started under a DIY low tunnel.
These temporary structures are basically ‘low to the ground’ greenhouses, hence the ‘low’ tunnel. The simple, arched structures are efficient at trapping passive solar heat and holding it in the soil. In Minnesota we often get snow into April, so the reinforced arches are key to keeping plants happy during spring storms.
Inexpensive and easy to build, low tunnels can be popped up anywhere, so they’re perfect for small space gardens. They also work well with crop rotation, as you can move where you’re growing your earliest crops each season.
Starting seeds is something Nature does effortlessly… at least it looks like it from our garden bench doesn’t it?
Successful seed starting for us gardeners is about combining the right timing, light, seeds, and seed starting mixes all together. And when starting seed indoors, we control every element, including the seed starting mix.
For modern homestead gardeners, a high-quality seed starting mix creates the foundation for strong roots, healthy growth, and resilient seedlings when starting seeds indoors.
While it can be tempting to scoop soil straight from the garden or grab any bag labeled “potting mix,” but seed starting mixes are a category all their own. They’re designed to support early plant growth using sustainable gardening practices that protect seedlings during their most vulnerable stage.
Come learn, commune, or just love on local with me early in the year!
I have many other private gardening and homesteading classes scheduled for Local Garden Clubs and Master Gardeners as well. If you are interested in having me speak, I am taking reservations for next winter and spring now. Please email me at michellenbruhn@gmail.com if you’re interested.
You can also see a full list of my class topics HERE.
I love how my book collection keeps growing, just like my plant collection!
OK, so I have a thing for books…
Gardening “How To” books, Ecological Gardening books, Permaculture, No Dig, Companion Planting, Preserving, Homesteading… I’ve read a lot of books. And, not all of them earn a place on my bookshelf.
Nothing quite compares to flipping open to a page to find that bit of info, recipe or inspiration. Below are some of my most loved Garden and Local Food books.
Each of the books listed below would make great gifts, and a welcome addition to any gardener, homesteader, or foodie’s library!
Gardening, at its heart, is good for you AND the planet! But years of green washing and less than organic practices have made it a little confusing. But there are some basic tips I’ve learned to help you get gardening for sustainability.
Intensive companion planting and staggered succession planting creates a thriving vegetable garden and happy harvests!
Sustainable gardening is all about creating a living system that supports itself, nurtures the environment, and… actually gets easier for you over time. It’s the sweet spot where ecology meets practicality.
When you plan to manage each precious resource—from water, soil, sun, and plant matter—you’ll see the soil grow richer each year and the workload become more manageable. The garden will start to function like the ecosystem it is rather than feel like a chore.
For Minnesota gardeners and especially organic, permaculture-minded homesteaders, this mindset fits beautifully with our distinct seasons, rich glacial soils, and wildly resilient native species.
This is such a warming soup. I’ve made a few variations in the past but have settled on this as a family favorite. I recently made this for a recovering friend, and I think it’s a perfect hug in a jar.
I also recently harvested all of these main ingredients from our suburban homestead here in Minnesota. Yes, even the ginger. So this soup sums up my most recent fall harvests in one bowl.
And as with all soups, this recipe is a jumping off point. A half cup more or less of any of the main ingredients is not going to ruin this soup. It is lighter and brighter than the more common butternut squash soup, but it certainly looks like that other orange fall soup. I am always looking for ways to sneak in more protein, so of course I add white beans to this soup. Adding beans to any blended soup gives it a creamy, thicker consistency along with all the other health benefits.
