Hunkie, Montana is very doable gardening. That's why the experience of neighbors is so important, and experienced and wise persons at nurseries there is so important. (Nurseries in California have a huge list of species for the employees and owners to know. Montana that list is smaller, but they need to know all the growing tricks and tips, and to be able to say, no mayaam, Wisteria will not make it through the first winter, but Honeysuckle Vine or Silverbells are really fine, even tropical looking.)
A season from sometime usually in early June to usually sometime in September is actually pretty good for a lot of things. Some good number of folks push the limits and set out 2 or 3 month old Yellow Brandywine starts for example, and might have fence posts to drape blankets over the plants those first few light frost weeks at night. No need to be stuck only with early girl!
Even barely zone 4 has some glamorous and exotic looking plants! Valiant Grapes, a good number of apple varieties, some prunes, plums, even a couple Apricots. (((forget peaches though.

we tried and tried))) the new bush roses from weeks are mostly zone 4 good and not grafted, so even almost hybrid teas can grow there. Tropicana hybrid tea grows good, and stays smallish.
You should see how resourcefull some gardeners are in Montana! Thin a Juniper just right and it looks like it's from Japan. Oriental Lilies tucked between, set in some Bishops Children red leaved Dahlias, and let one of the many creepers fill in...House hardly looks like it belongs in Montana!
One guy even added some hillocks, and put in a small stream, and a pump operated waterfall, set in flat wide stones, sets his bonsais outside