Peppers are one of those vegetables that people in Missoula either swear by or give up on after one bad season. Often the problem is not the gardener. It is usually the variety, the timing, or both.
Growing peppers in Montana is possible, but you have to be honest about what you are working with. Peppers want heat more than almost anything else in the vegetable garden. They want warm soil, warm days, and warm nights. Missoula can deliver the days, but the nights are the tricky part.
Why Peppers Are Harder Than Tomatoes Here
Tomatoes cope with cool nights reasonably well. Peppers are fussier. University of Maryland Extension notes that nights below about 60 degrees, or very hot days above 95, can cause pepper flowers and small fruit to drop, and cool nights also slow the plants down overall. Missoula’s summer nights are often cooler than that, so peppers tend to grow and set fruit more slowly here than in warmer places, which shortens an already short season.
The other issue is that bell peppers take a long time to fully ripen. Many standard bell varieties need 70 to 80 days from transplant just to reach full-size green fruit, and then several more weeks to turn their final color. Missoula’s frost-free season runs about 130 days in a typical year (NOAA’s 1991 to 2020 normals for the airport), and less in a cold year or a frosty yard, so that is a tight squeeze, especially with cool nights in the mix.
The solution is not to abandon peppers. It is to pick varieties that are actually suited to this climate and give them every advantage you can from the start.
Varieties That Actually Work in Montana
For sweet peppers, look for varieties that mature in 60 to 70 days or less and do not require a long, hot summer to produce well. Pepper days to maturity are counted from transplanting, not from seeding, and the numbers vary a little from one seed company to the next, so use them to compare varieties rather than as a calendar.
Ace is an extra-early bell pepper. Johnny’s Selected Seeds lists it at about 50 days to full-size green fruit and 70 days to red, and describes it as performing particularly well in cool climates where bells are hard to grow. Pick it green, or leave some fruit on to turn red if the season gives you enough time.
Lipstick is a thick-walled, flavorful sweet pepper of the pimento type, with tapered fruit that ripens red in about 70 to 80 days. Baker Creek describes it as doing well even in northern climates with cooler summers.
Carmen is an Italian frying pepper bred by Johnny’s Selected Seeds. It is ready to pick green in about 60 days and turns red in about 70 to 80 days, depending on the catalog. It is sweet and productive, and Johnny’s describes it as early and adaptable.
Banana peppers in general are solid options for Missoula because they mature faster than many bells and are usually picked at the pale yellow stage, before they turn orange or red.
For hot peppers, you actually have more options. Jalapenos are usually picked green, in about 65 to 70 days, which makes them a good place to start. Cayenne, Thai hot, and serrano peppers take longer, about 75 to 90 days to ripen, so start them early and give them your warmest spot.
Start Seeds Early and Harden Them Off Carefully
MSU Extension gives peppers 6 to 8 weeks indoors to reach transplant size, and about 8 weeks is a common target because peppers are slow to germinate and slow to size up. Slow varieties can go up to about 10 weeks if you have strong grow lights and room to pot them up. Count back from the date you plan to transplant. For a late May or early June planting, about 8 weeks means sowing in late March or early April, a little ahead of most tomatoes.
They need consistent warmth to germinate well. A soil temperature of 80 to 85 degrees is ideal for germination. A seedling heat mat is worth it for peppers. Without that bottom heat, germination is slow and uneven.
Do not rush transplanting. Peppers are frost tender and stall in cold weather. 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. University of Minnesota Extension suggests waiting until night lows are above 50 degrees, but Missoula nights often dip below that even in midsummer (NOAA’s normals put the average summer low at the airport near 49 degrees). In practice, peppers usually go in from late May into early June, after a look at the 10-day forecast, with water walls or row cover ready for cool nights. The Missoula frost dates and planting calendar is a useful reference for timing.
Harden them off gradually before moving them outside full time. MSU Extension suggests two to three weeks for warm-season crops like peppers. Going straight from a warm indoor environment to Missoula spring air is a shock peppers do not recover from quickly.
Give Them Every Bit of Heat You Can
Peppers respond visibly to heat. The more you can do to keep them warm throughout the season, the better they tend to produce.
Use water walls, such as Wall-o-Water, or a row cover when you first transplant. Both hold warmth around young plants on cool nights and help them settle in. Take water walls off once the plants grow out of the top.
Be careful with mulch early in the season. Organic mulches like compost, straw, or shredded leaves hold moisture but keep the soil cooler, so wait until the soil has warmed, usually late May to June here, before spreading them around peppers. To warm the soil, plastic film works better. University of Minnesota Extension recommends black plastic for peppers, though in MSU Extension’s trials in Bozeman, black plastic did not significantly raise soil temperature while red plastic film did.
Plant peppers in your warmest, most sheltered spot. A south-facing bed against a wall or fence is ideal. Dark-colored containers also warm up quickly in the sun, which helps early in the season, though they dry out faster in midsummer. Through Missoula’s dry midsummer weeks, consistent watering becomes just as important as heat. The guide on dealing with Missoula’s dry summers in the garden covers what to watch for when conditions turn hot and dry.
If you get to late August and still have a lot of green peppers on the plant, leave them. They will keep sizing up and coloring, though slowly once nights turn cool. When frost threatens, pick them all. Missoula’s median first fall frost is late September (about September 26), and in about 1 year in 10 it arrives by mid September.
Green Peppers Are Still Worth Eating
Here is something worth accepting if you grow peppers in Montana: you may eat most of them green. That is not a failure. Green bell peppers are edible and perfectly good to eat, but they are not ripe. Left on the plant, colored varieties keep developing sweetness until they reach their final color, usually red, yellow, or orange.
If you go in expecting that rather than holding out for a box of red bells, you will feel a lot better about your pepper season. And every fully ripe one you do get feels like a win.
For more variety ideas, see the best pepper varieties for Montana’s short season.
Sources
- Montana State University Extension, Can I Grow That Here? Vegetable Seed and Transplant Schedules
- Montana State University Extension, Successful Home Vegetable Gardening
- University of Minnesota Extension, Growing Peppers
- Montana State University Extension, Growing Tomatoes in Montana
- University of Maryland Extension, Poor Blossom and Fruit Set of Vegetables