Companion planting is the idea that some plants grow better next to certain neighbors. Some of it is solid, backed by how plants actually interact, and some of it is garden tradition that has been passed around so long people assume it is proven. In a Missoula garden, where space and season are both limited, the parts that work are worth using, and the parts that are just folklore are worth knowing about so you do not count on them.
I lean on the approaches that have a clear reason behind them: attracting pollinators, making the most of vertical and horizontal space, and using flowers to support the whole garden ecosystem. Here is how I think about companion planting for our short season.
Plant Flowers to Bring in Pollinators
This is the companion planting principle with the most behind it. Many of your vegetables, squash, cucumbers, beans, and tomatoes among them, produce better when pollinators are active and abundant. The way to bring them in is to give them something to feed on right in and around the vegetable beds.
MSU Extension makes the point that the best way to support a range of pollinators is to plant a diversity of flowers that bloom at different times, so there is always something in bloom through the season. Tuck flowers like calendula, borage, cosmos, and zinnias among your vegetables, and let a few herbs like cilantro, dill, and basil flower at the end of their run. The bees and beneficial insects that show up for the flowers stick around to work your vegetable blossoms too.
This fits the way I like to garden anyway. A vegetable bed with flowers woven through it is more alive, more resilient, and frankly nicer to spend time in than a bare grid of single crops.
Use Space in Layers
The most practical side of companion planting in a short season is fitting more into the space you have. Pairing plants that use space differently lets you grow more without crowding.
The classic example is the Three Sisters: corn, beans, and squash. Corn grows tall, beans climb the corn stalks, and squash sprawls across the ground below, shading out weeds and keeping the soil cool. It is a genuinely smart use of vertical and ground space, though corn can be a stretch in a cool Missoula summer, so give it your warmest, sunniest spot if you try it.
You can use the same thinking on a smaller scale. Plant quick crops like radishes or lettuce between slower ones like tomatoes or peppers, and you will harvest the fast crop long before the big plants need the room. Grow trailing crops at the base of a trellis so the vertical and horizontal layers do not compete. MSU Extension also recommends putting tall crops like corn on the north side of the garden so they do not shade everything else.
Pairings Worth Trying
A few combinations are popular for good reason. Basil planted near tomatoes is a natural fit since both want the same warm conditions, and the basil flowers draw pollinators when you let a little of it bloom. Carrots and onions are often grown together, with the strong onion smell thought to confuse the pests that hunt by scent. Lettuce and other greens appreciate a bit of afternoon shade from taller neighbors during the heat of summer, which buys you a longer harvest before they bolt.
Marigolds get planted throughout vegetable gardens everywhere, and while some of the pest-repelling claims are overstated, they are tough, they bloom all season, and they add color and pollinator food. There is no harm in tucking them around, just do not expect them to replace good garden practices.
Where Companion Planting Falls Short
It is worth being honest that a lot of companion planting charts online treat tradition as fact. Some pairings have real reasoning, and others are repeated so often they sound official without any evidence behind them. If a claim sounds too tidy, treat it as an experiment rather than a rule, and lean on what MSU Extension recommends for our region.
The fundamentals matter more than any pairing: healthy soil fed with compost, steady water, full sun for the crops that need it, and a diversity of plants that keeps the garden balanced. Companion planting works best as one more tool on top of those basics, not a replacement for them.
If you want help designing a Missoula garden that uses space well and supports pollinators from spring through fall, that is exactly what I do. Take a look at the vegetable garden consulting page and reach out.