Article by Ed Quillen
Climate – May 1994 – Colorado Central Magazine
This is when even devout non-gardeners like me drool uncontrollably over seed catalogs. Every four-color variety of squash, bean or melon looks comely, even luscious — and then there’s the fine print:
GROWING SEASON 170 DAYS.
You can get a general idea of local growing seasons from the average date of last killing frost and average date of first killing frost:
LOCALE Elev. Last First Days
GUNNISON 7,703 June 27 Aug. 22 56
WHITEPINE 9,900 July 2 Sept. 4 64
LEADVILLE 10,152 June 19 Aug. 26 68
FAIRPLAY 9,953 June 14 Aug. 31 78
CRESTONE 8,000 June 6 Sept. 6 92
WESTCLIFFE 7,888 June 10 Sept. 13 95
BUENA VISTA 7,954 June 6 Sept. 14 100
SALIDA 7,033 May 31 Sept. 12 104
SAGUACHE 7,697 June 3 Sept. 16 105
CAÑON CITY 5,332 May 2 Oct. 13 164
Actual growing seasons vary considerably. For instance, Cañon’s average last frost is May 2, but it has suffered killing cold as late as June 12, and as early as Sept. 12. At higher elevations, especially above 9,000 feet, there are years that don’t have growing seasons — last frost on July 31, and first on Aug. 2.
For plants that are real sensitive to frost, like tomatoes, it’s best to go inside the averages. Leon Stanton, Chaffee County extension agent for many years, advised that the safe time to set out tomatoes is about nine days after the average last frost. That is, Average Date of Last Killing Frost in Buena Vista is June 6, so Buena Vista Tomato Day is June 15.
Ask around about some local lore — in Salida, for instance, it’s usually safe to plant after the last visible snow has vanished from Methodist Mountain.
Elevation matters, but it’s not the only factor. Gunnison and Saguache are both about 7,700 feet high, and yet Saguache enjoys 105 days while Gunnison shivers under but 56 days — its season is shorter than Leadville’s, and Leadville is almost half a mile higher than Gunnison. Even Whitepine, in the same drainage but 2,000 feet higher, has a longer growing season than Gunnison. ( Whitepine, up at the head of Tomichi Creek, isn’t real populated now, but the 1937 Colorado Yearbook had statistics, and we take our numbers where we can find them.)
Cold air flows downhill. If it hits a basin above a narrow canyon, it can’t keep flowing, so it settles. Thus the valley floor is colder than the surrounding hillsides.