Most of the worry in a Missoula garden goes toward the warm-season crops, the tomatoes and peppers and squash that need babying through our short summer. But there is a whole group of vegetables that does the opposite. Cold-hardy crops actually prefer our cool weather, handle frost that would kill a tomato, and several of them taste sweeter after a cold snap. If you want a garden that produces from early spring well into fall, these are the plants that make it happen.
MSU Extension’s planting schedules rate many of these crops as hardy, meaning they can go in weeks before the last spring frost. In a climate like ours, leaning into the crops that handle cold is one of the smartest moves a gardener can make.
What Cold-Hardy Actually Means
Cold-hardy vegetables tolerate frost and keep growing at temperatures that stop warm-season crops cold. Some can come through hard freezes in fall, and a few can even overwinter under mulch and come back in spring. How much cold a plant takes depends on the crop and variety, how well it has adjusted to cooling weather, its age, and how long the cold lasts, so treat frost hardiness as a guide rather than a promise. This matters in Missoula because it stretches your season at both ends. Missoula’s median last spring frost is mid May (about May 16 at the airport, per NOAA’s 1991 to 2020 normals), and the median first fall frost is late September (about September 26). Low spots often run colder. You can plant cold-hardy crops weeks before that spring date and keep harvesting them past the fall one.
Many of these vegetables also get sweeter after a frost. When temperatures drop, the plants convert some of their starches to sugars, which acts like a natural antifreeze. Carrots, kale, and Brussels sprouts are known for this, and MSU Extension notes that Brussels sprouts harvested after moderate freezes are much sweeter.
The Most Reliable Cold-Hardy Crops
Kale is one of the toughest. It handles cold better than most garden crops, often keeps producing through fall frosts, and tastes sweeter for it. Plant it in spring and again in midsummer for a fall crop and you can harvest leaves for months.
Spinach is very cold-tolerant and germinates in cold soil, though it bolts quickly once it warms up. It is often a better fall crop than a spring one here. Swiss chard bridges the seasons, handling both cool weather and summer heat, and a single planting can produce from spring until a hard freeze.
Carrots and beets are dependable cold-hardy root crops. Both handle cool soil, and carrots especially turn sweet after fall frosts. You can leave them in the ground under mulch and dig them as needed into late fall.
Peas are a classic early crop, going in as soon as the soil can be worked in spring and tolerating light frost while they grow. Broccoli, cabbage, and Brussels sprouts are all cold-hardy too. Brussels sprouts in particular are a long-season crop best timed to mature in the cool of fall, when frost improves their flavor.
Plant Them Twice
The real advantage of cold-hardy crops is that you get two windows to grow them. The first is early spring, when you can plant well before the last frost while warm-season crops are still weeks away. The second is mid to late summer, when you plant again for a fall harvest that matures in cooling weather.
That fall planting is the one most people skip. In late July and into August, as you pull spent summer crops, drop in another round of kale, spinach, lettuce, and other cold-hardy greens. MSU Extension’s schedule puts fall spinach and kale about 6 to 8 weeks before the first fall frost and lettuce up to 6 weeks before, which in Missoula means late July to mid August. They size up in the cooling weather and often produce better than spring plantings because they are not racing the heat. Keep a corner of the garden in mind for this so the space is ready when the time comes.
Stretching the Season Even Further
Cold-hardy does not mean indestructible, but a little protection goes a long way. A row cover or a cold frame thrown over a bed of greens can keep them producing past the first frosts, often by several weeks depending on the weather, and under a thick straw mulch, carrots and other roots can hold in the ground for digging into the cold months, until the soil freezes hard.
None of this requires much work, just a shift in thinking. Instead of treating the first frost as the end of the garden, treat it as the start of the cold-hardy season. With the right crops, a Missoula garden can keep feeding you long after the tomatoes are gone.
For crop-by-crop spring and fall planting dates, see the Missoula Planting Calendar.
Sources
- Montana State University Extension, Can I Grow That Here? Vegetable Seed and Transplant Schedules
- NOAA NCEI, U.S. Climate Normals 1991 to 2020 (Missoula International Airport)