Lettuce is one of the few crops in Missoula that rewards you for being impatient. While you are waiting on tomatoes and peppers to wake up, you can be cutting salad greens. Most of them tolerate cool weather, a few even shrug off a light frost, and the whole group grows fast enough that you can plant again every couple of weeks and never run out.
The catch is heat. Lettuce and most salad greens are cool-season crops, which means they do their best work in the cooler parts of spring and fall. Once Missoula hits its July stretch of hot afternoons, a lot of these plants turn bitter and shoot up a flower stalk. Knowing how to work around that is most of the battle.
When to Plant Salad Greens in Missoula
You can start much earlier than you might think. MSU Extension’s planting schedule puts lettuce in the ground about 4 weeks before the average last spring frost, and spinach about 6 weeks before. Missoula’s median last spring frost is mid May (about May 16 at the airport, per NOAA’s 1991 to 2020 normals), so that means lettuce from about mid April and spinach from early April, depending on how the weather is behaving that year.
Lettuce seed germinates in cool soil that would stall a tomato. MSU Extension gives a soil temperature range of 45 to 75 degrees for lettuce germination, so it will sprout once the soil is in the mid 40s, though it comes up faster in warmer soil. Frost tolerance varies by variety and plant size, but hardened young lettuce usually takes a light frost, so an early planting is a fairly low risk. If a hard freeze is coming, throw a row cover or an old sheet over the bed overnight and pull it off in the morning.
The bigger move is to keep planting. A single April sowing gives you one wave of lettuce and then it is gone. Instead, sow a short row every two weeks through spring. This is called succession planting, and it is the difference between a glut of lettuce in June and a steady supply from May into summer.
The Greens Worth Growing Here
Leaf lettuce is the easiest place to start. Loose-leaf types like oakleaf and red and green leaf varieties grow quickly and let you pick outer leaves while the plant keeps producing from the center. You get weeks of harvest off a single planting instead of one head and done.
Romaine and butterhead types form looser heads and take a little longer, but they handle our cool nights well and have better texture than most leaf lettuce. If you want a crisp head lettuce, give it your earliest spring planting so it matures before the heat arrives.
Spinach is the cold champion of the group. It germinates in genuinely cold soil and grows fast in spring, but it bolts quickly once days get long and warm. Plant it early, harvest it hard, and do not expect it to last into midsummer. That is why a fall spinach crop is often more productive than a spring one.
Then there are the greens that fill the gap when lettuce struggles. Arugula grows fast and adds a peppery bite, though it bolts quickly in heat too. Kale and Swiss chard are the workhorses. Both are technically cool-season but far more forgiving of summer than lettuce, and chard in particular will keep going from spring until a hard fall freeze. If you want something in the salad bowl all season, these two carry you through July and August when the lettuce has given up.
Keeping Greens Going Through the Heat
When a lettuce plant bolts, it stretches upward, the leaves turn bitter, and that is more or less the end of it. You cannot reverse it, but you can delay it. A few things help in a Missoula summer.
Afternoon shade is a useful trick. MSU Extension notes that lettuce and spinach actually do fine with some shade during the day, so a spot that catches morning sun and gets relief from the hot afternoon will hold your greens longer than a fully exposed bed. If you do not have a naturally shady spot, taller crops like pole beans or trellised cucumbers can throw shade onto a lettuce row planted on their east side.
Steady water matters just as much. Greens have shallow roots and dry out fast, and heat stress plus dry soil helps push them to bolt. Water deeply and keep the bed evenly moist rather than letting it swing from soaked to bone dry. A layer of straw or another light mulch around the plants keeps the soil cooler and holds moisture between waterings, which is worth a lot in our dry July weather.
Choosing heat-tolerant and slow-to-bolt varieties helps in the hottest part of summer, and seed packets usually say which ones those are. But the bigger lever is the calendar. Grow most of your lettuce in spring and fall, lean on kale and chard through the worst of the heat, and start a fresh round of greens in August for a fall harvest once the nights cool off again.
A Fall Crop Is Worth Planning For
A lot of people plant salad greens once in spring and forget about them. Missoula’s median first fall frost is late September (about September 26), and in about 1 year in 10 it arrives by mid September. MSU Extension’s schedule puts fall spinach in about 6 to 8 weeks before the first frost and lettuce up to about 6 weeks before, which means early to mid August here. Both handle light frost once they are established, and cool weather can make some greens taste sweeter than ones that matured in summer heat. Mark a reminder for yourself in late July so you do not miss the window.
For spring and fall sowing dates for greens and the rest of the garden, see the Missoula Planting Calendar.
Sources
- Montana State University Extension, Can I Grow That Here? Vegetable Seed and Transplant Schedules
- Montana State University Extension, Successful Home Vegetable Gardening