In Missoula, the growing season feels short because it is. With our average last spring frost around May 19 and the first fall frost around September 22, you get roughly four months of frost-free weather, and the warm-season crops want every day of it. The good news is that you do not have to accept those dates as hard limits. With a few simple tools and some planning, you can start earlier in spring and keep harvesting weeks later in fall.
Extending the season is not about expensive greenhouses. Most of it comes down to trapping warmth, protecting plants from frost, and timing your plantings well. Here are the approaches that work in our climate.
Get a Head Start in Spring
The simplest way to lengthen your season is to start plants before the weather is ready for them outside. Starting seeds indoors gives heat-loving crops like tomatoes and peppers a head start of several weeks, so they are already established when the soil finally warms. This matters a lot here, where those crops need all the warm time they can get.
Out in the garden, a few tools let you plant sooner. Row covers, which are lightweight fabric draped over the bed, trap warmth and protect young plants from late frosts. Cloches, basically individual covers set over single plants, do the same on a small scale. For tomatoes, water-filled season extenders that circle the plant store daytime heat and release it at night, letting you set them out a couple of weeks early. All of these buy you time on the front end of the season.
Warm the Soil
Cold soil holds plants back even when the air feels warm, so warming the ground is part of extending the season. Raised beds naturally warm earlier in spring because they drain better and the sun reaches more of the soil. Covering a bed with a row cover or cloche for a week or two before planting raises the soil temperature several degrees, which gets seeds germinating and transplants growing sooner.
This early warmth is especially useful for the warm-season crops that sulk in cold ground. A little soil warming up front can mean the difference between a crop that ripens and one that runs out of time.
Stretch the Fall With Covers and Cold Frames
The back end of the season is where you can gain the most, because so many cool-season crops keep going well past the first frost if you protect them. A row cover thrown over a bed of greens on a frosty night can keep them producing for weeks after unprotected plants would have died.
A cold frame takes this further. It is a simple bottomless box with a clear lid, set over a bed, that acts like a tiny greenhouse. Crops like lettuce, spinach, kale, and other hardy greens will keep growing inside one well into the cold months. Low tunnels, which are hoops covered with row cover fabric or clear plastic over a bed, do the same thing on a larger scale and are easy to put up and take down. None of these are complicated or expensive, and they dramatically extend how long your garden produces.
Plan Your Plantings Around the Season
Tools help, but timing is just as important. Succession planting, sowing small batches of fast crops every couple of weeks, keeps fresh harvests coming instead of everything maturing at once. And the fall garden is the most overlooked opportunity here. In late July and into August, as summer crops finish, plant another round of cold-hardy greens and root crops. They mature in the cooling weather and, with a little cover, produce long after the first frost.
Choosing short-season and cold-tolerant varieties ties it all together. A variety that matures in 55 days instead of 75 effectively extends your season by giving the crop time to finish. Combined with the warmth-trapping tools above, the right varieties let you grow more in our short window than the calendar would suggest.
If you want help setting up season extension and planning a garden that produces from early spring into late fall, that is exactly what I do. Take a look at the vegetable garden consulting page and reach out.