When I moved to Jackson Hole decades ago I sometimes walked around town to check out which plants were rugged enough to grow in this mountain climate. I had moved here from the long warm seasons of southern Utah where sweet corn, watermelons and beefsteak tomatoes thrived. I grew so many tomatoes, in fact, that I once used them to play ball with my dog.
Gardening was sure to be more of a challenge in Jackson Hole.
One flower I noticed had been frequently planted was a red lychnis, which I found out is a variety called “Maltese cross.” This plant is a long-lived, old-timey favorite that is very cold hardy. Apparently, a perfect perennial for a wicked climate. I found it growing in front of old hotels and houses and reckoned it had been growing in those places for years.
But what exactly does “cold hardy” mean?
To garden at high altitudes it helps to pay attention to the plant’s rating on the U.S. Department of Agriculture’s hardiness zone maps you often see in seed catalogs and gardening books and on seed packets and the plastic label tags stuck in nursery plants. Horticulturists and meteorologists have mapped North America into 10 zones of average and maximum temperatures.
Northwest Wyoming is overall a place considered to be in Zone 3 (or sometimes 4). (with Zone 1 being the coldest and Zone 10 the warmest.) Zones have to do with the average lows, but the reality is that at high altitudes it can freeze at any point that affects the growing season. The rating given a plant indicates it can survive average conditions in that zone.
Now, annual flowers aren’t really a concern when deciding what to plant. You see, they are only one-summer plants. They will die in the fall and not come back in the spring no matter what you do. Think petunias, marigolds, alyssum, lobelia, zinnias and many others whose lifespans are only one season.
It is with the perennials that we need to know whether they are cold climate-hardy enough to withstand a harsh winter and grow back again from their roots in the spring.
In a climate where spring is painfully late, perennial flowers awaken as the snow retreats.
Some other perennial flowers that are winter hardy are Shasta daisies, heliopsis, Oriental poppies, Gypsophilia (baby’s breath), Gaillardia daisies, speedwell, hardy geraniums, the campanulas, lupines, columbines and coneflowers.
And, of course, Maltese cross. I’ve had clumps of this dependable plant in my gardens for years and years. This species prolifically self-sows, scattering its little round black seeds all over the garden. Each summer I find lots of volunteers in all sorts of nooks and crannies in my perennial borders.
Surprisingly, some of these wildlings have reverted to blooming with white blossoms instead of scarlet. This sometimes happens a few generations away from the original plants. The plants may start to look more like their ancestors before plant breeders fiddled with them. Columbines may lose their diverse colors and are mostly pale yellow. Petunias revert back to a pale (but lovely) pink.
I rather like these simple color changes because I think the blooms look more like wildflowers, which I can never get enough of in the mountains.