I cringe every time I hear a television newscaster announce that on Mother’s Day it’s safe to set out your tomatoes and annual flowers. Mother’s Day was a week early this year. The average late frost date for Denver may be the first week in May, but keep in mind that averages are just that.
Outlying areas experience last average frost dates a week or two later than Denver’s. Snow in June is not unheard of anywhere on the Front Range. Where I live — at 660 feet higher in elevation than the Mile High City — mid-May is a safer bet.
I’ve been stockpiling plants since the beginning of April. In years past I’ve learned that if you have your heart set on something, even as mundane as a particular blue petunia, you’d better grab it the first time you see it. Otherwise I can promise you fruitless searches throughout the Denver area trying to locate what ought to be the gardening equivalent of buying a dozen eggs or a gallon of skim milk.
Hardy plants have been going out into the garden in waves between storms. First they bivouac on the back patio for at least a few days while building up tolerance for Colorado’s erratic temperature swings, high UV light and low atmospheric humidity (the more lush the plant, the longer its patio stay). As seedlings of frost-tolerant vegetables and flowers move up from seed pot to 6-pack, they also go outside to join the patio throng in what, for much of April and May, resembles a plant refugee camp.
Non-hardies, like begonias and tomatoes, have been spending much of their time on the family room floor — to the delight of the resident house cats who are convinced that I’ve brought the gardens indoors just for their amusement. On nice days, these go outside in the morning and then come back inside in the evening where it’s safe and warm (on a plastic drop cloth to protect the carpet). On the few balmy nights where temperatures were warm, these, too, got to sleep under the stars.
Today, unless it snows, the plants can finally vacate the family room. Container-bound begonias, cannas, dahlias and the like must wait until June 1 to make their garden debut. Having made their annual migration from the garage to grow lights in the basement weeks ago, these tropicals have been fooled into believing that they’re enjoying an equatorial spring. They can’t go outside until the threat of frost is well past.
In any case, be prepared for late frosts and June snows. Frost blankets, sold in every major garden center on the Front Range, are a spring essential (old sheets and blankets can work in a pinch). Wherever you live, keep an eye on the weather forecast and be prepared to cover your tender flowers and vegetables whenever the need arises. After all, this is Colorado where, weatherwise, anything can happen.
Garden writer and lecturer Marcia Tatroe’s most recent book is “Cutting Edge Gardening in the Intermountain West,” ($29.95, Johnson Books). E-mail her at rltaurora@aol.com.
