Most gardeners in Missoula wait until late May to plant anything, and for tomatoes and peppers, that’s the right call. But there’s a whole category of vegetables that not only tolerate cold weather but actually prefer it. If you’re only gardening after last frost, you’re missing weeks of good growing time.
What “Before Last Frost” Actually Means in Missoula
Missoula’s median last spring frost is mid May (about May 16 at the airport, per NOAA’s 1991 to 2020 normals), but in about 1 year in 10 it comes after June 1, and low spots often run colder. “Before last frost” doesn’t mean you’re gambling with your whole garden. It means there are vegetables that can handle those temperatures, and knowing which ones lets you get a real head start on the season.
MSU Extension’s planting guides sort vegetables by how much frost they tolerate, and each crop gets its own window. Hardy crops such as peas, spinach, lettuce, and cabbage can go out weeks before the last frost, often with nothing more than a row cover for the coldest nights. Frost-sensitive crops like tomatoes, peppers, and cucumbers have to wait until the danger of frost has passed. Understanding that distinction changes how you think about spring gardening in Montana.
Leafy Greens and Salad Crops
Lettuce, spinach, arugula, and mixed salad greens are among the most cold-tolerant vegetables you can grow. MSU Extension’s schedule puts spinach in about 6 weeks before the last frost, which is early April in a typical Missoula year, and lettuce about 4 weeks before, around mid April, either as transplants or direct-sown seed. They often do better in cool weather than they do in summer heat, and once hot weather settles in they tend to bolt and turn bitter. Getting them in early gives you the most productive window.
A light row cover or low tunnel can push this a little earlier and protects young plants on the coldest nights. MSU Extension calls low tunnels ideal for early-spring leafy greens. Hardened lettuce stands light frost, and spinach is hardier still, but a hard freeze can still damage tender new growth, so keep a cover handy.
Brassicas: Broccoli, Cauliflower, Kale, and Cabbage
Broccoli, cabbage, kale, and kohlrabi are all hardy enough to go out well before the last frost. MSU Extension’s schedule puts broccoli and cabbage transplants out from about 6 weeks before the last frost, early April in a typical Missoula year, and kale and kohlrabi from about 5 weeks before. Cauliflower is fussier and waits until about 3 weeks before. Those are the earliest dates, so many gardeners plant later in April or early May, depending on the year and their yard, and harden transplants off first.
Hardened brassica transplants can take a light frost without much trouble. A hard freeze can still damage them, especially plants that went out recently or were not hardened off, so if one is forecast after you’ve transplanted, drape a row cover or old bedsheet over the plants overnight. A cover adds a few degrees of protection, so it helps more on a borderline night than in a deep freeze.
Kale is one of the toughest of this group. It comes through light frosts with little damage and often tastes sweeter after a cold snap, which makes it an easy cold-season crop to start with in a Missoula spring.
Peas
Peas are usually direct-sown rather than transplanted, and they germinate in cool soil (MSU Extension lists 40 to 70°F for pea germination). MSU’s schedule puts them in about 4 to 6 weeks before the last frost, early to mid April in a typical Missoula year, as soon as the soil can be worked. Peas grow best in cool weather, and hot weather during flowering and pod fill cuts the harvest. Sow them in late May and they run out of cool weather before they can produce much.
Get peas in early, let them climb, and plan to pull them out in July when the heat arrives and they start to die back. You can replant that space with a summer or fall crop. Peas are one of the few things in the garden that actually do better the earlier you get them in.
Root Vegetables and Chard
Beets, carrots, radishes, and turnips can all be direct-sown before last frost, about 4 weeks before for beets and carrots and as early as 6 weeks before for radishes and turnips, per MSU Extension. They tolerate light frost and are simple to get started. Radishes are the fastest of the group, ready to harvest in 25 to 30 days, which makes them a good option for filling gaps early in the season.
Chard is hardy too. It can be direct-sown about 4 weeks before the last frost or set out as a spring transplant. It produces all season and handles both cold springs and warm summers better than most leafy greens.
Before You Plant
Soil temperature matters as much as air temperature. Cold soil slows germination and can rot seeds before they have a chance to sprout. A simple soil thermometer tells you what the ground is actually doing. MSU Extension’s soil temperature ranges for germination start at about 40°F for spinach, peas, and radishes, 45°F for lettuce, 50°F for beets, and 55°F for carrots, and seeds come up faster toward the warmer end of each range.
Missoula’s spring wind can also be as hard on transplants as the cold. Newly planted seedlings in exposed beds can dry out or get physically damaged on a windy April day. Planting in a somewhat sheltered spot, or using a low row cover that blocks wind, helps a lot in the first few weeks after transplant.
For crop-by-crop dates through the whole season, see the Missoula Planting Calendar, and for getting transplants ready, Hardened-Off vs. Greenhouse Starts.
Sources
- Montana State University Extension, Can I Grow That Here? Vegetable Seed and Transplant Schedules
- Montana State University Extension, Successful Home Vegetable Gardening
- Montana State University Extension, Hotbeds, Cold Frames, and Low Tunnels for Montana Gardeners
- NOAA NCEI, U.S. Climate Normals 1991 to 2020 (Missoula International Airport)