Deb Babcock: Gardening in our climate
May 3, 2010
Nolan Doesken, of the Colorado Climate Center, visited Steamboat Springs last month to talk with master gardeners and their guests about our local climate.
It's an important topic for home gardeners because our climate dictates which plants will flourish here and which ones will take a lot of work to keep healthy.
Colorado, and in particular Routt County, boasts some of the highest city elevations in the United States. With our middle-of-the-country interior location and our complex mountain topography, we experience some of the biggest seasonal changes in the world for our latitude.
We are one of the snowiest places in the Northern Hemisphere, Doesken said, with relatively little variation from year to year. He compares our weather to that of the Tibetan Plateau, which shares our 40 to 41 degree latitude.
Luckily for us and thanks to a consistent moisture source — the Pacific Ocean — we live in the wettest area of the interior western United States, with Buffalo Pass being at the top of the list of wet areas.
So what does all this mean for gardeners? It means we need to choose plants for our gardens that can withstand huge temperature swings — from just above freezing at night to 80- and 90-degree highs during the day in summer. It means that our perennials and trees will get plenty of moisture from winter snowmelt but that as the summer moves along, it will be dry, hot and windy.
As you look for plants to grow, consider natives that are used to our mountain climate. Among perennial flowers, this includes columbine, lupine, geranium, larkspur, penstemon, flax, harebell, evening primrose, coneflower, and wild iris. Among shrubs, this includes dogwood, willows, sagebrush, cinquefoil, chokecherry, serviceberry and mountain ash.
Vegetables grown successfully here include most of the root vegetables, such as potatoes, carrots, turnips and radishes. Lettuce, peas and beans grow well in our climate, as well.
There are two reliable indicators you should look for in plants you want to grow here. One is the U.S. Department of Agriculture cold hardiness zone and the other is the heat zone developed by the American Horticultural Society.
The USDA cold hardiness zone map was developed by gathering data from 7,000 weather stations throughout the country. Most of Steamboat is considered Zone 4, meaning that the annual average lowest temperature range between minus 30 and minus 20 degrees. Some local gardens experience even colder low temperatures and would be considered Zone 3, which drops to minus 40 to minus 30 degrees, while some areas never get lower than minus 20 degrees, which applies to Zone 5.
The AHS heat zone indicator also was compiled from weather station data, where daily high temperatures were recorded. The zone numbers are based on the average number of above-86-degree days, or "heat days," we experienced each summer. Zone 1 equals less than one heat day a year, while Zone 12 experiences more than 210 heat days per year. Steamboat falls into AHS Heat Zone 4. Again, if your garden faces south and receives no relief from the sun, you may need to purchase plants hardy in Heat Zone 5.
In catalogues and on plant information stakes in nurseries, you should look for these two numbers.
Spring weather is certain to be here before we know it. Plan your garden now so you're ready to plant it as soon as the weather cooperates.