In San Miguel Basin & Surrounding Areas
And the Hardiness of Vegetables and Flowers
Microclimates vary widely in the mountains. Often, the tops of sloping areas absorb more heat from the sun and allow cold air to drain off and so are a bit warmer than low-lying areas where frost can settle and are colder.
FROST-FREE GROWING SEASONS IN SMB & SURROUNDING COMMUNITIES
| Community | Dates of average ‘Frost-free’ Growing Season | Comments Frost Free ‘Growing Seasons’ are based on average (50% chance) last 32.5⁰ F frost in the spring and first 32.5⁰ F frost in the fall. **See Colorado Climate Summaries for official weather station data. |
| Norwood | June 9 – September 21 (104 days)** | The newest data reduced this by a week for first fall frost. |
| Redvale | Beginning of June through September/October* | May have slightly longer season with warmer daytime temperatures than Norwood* |
| Nucla | Beginning of June through September/October* | Somewhat cooler than Naturita but warmer and longer season than Norwood* |
| Naturita | Beginning of June through September/October* | Warmer, longer season than Norwood* |
| Paradox East | May 14- September 24 (133 days)** | |
| Paradox West | May 8- October 5 (150 days)** | Paradox/Bedrock have two weather stations |
| Telluride | June 28 -August 31 (64 days)** | Some locals use June 15th as the average last frost. ** |
| Placerville | July 19- August 15 (27 days)** | This is a short-season for an area referred to as the ‘banana belt’*. I question the reliability of this data. There seems to be a problem on the graphs. |
| Mountain Village/Ophir | There isn’t any official data for Mountain Village or Ophir. Local input would be valued. | |
| Uravan | May 2 – October 13 (164 days)** | No town there but there is a weather station, and this is the longest frost free growing season in the area! |
| Rico | July 1- Aug. 31 (61 days)** | |
| Ridgway | June 21- September 8 (79 days)** | Ridgway can have hard freezes in the summer months* (Ridgway Community Garden) |
| Ouray | May 29 – September 26 (120 days)** | Locals traditionally plant out on Memorial Day weekend * |
| Silverton | July 12 – August 15 (34 days)** | This is a big change (from9 to 34 frost free days) from past data |
**Data from 50++ years from weather stations (1948-2005)
HARDINESS OF ANNUAL FLOWERS
| Hardy annual flowers** | Tolerate cold soils and light frosts | Can plant out 4 weeks before average last spring frost date | Pansies, snap dragons, sweet alyssum, calendula, dusty miller, poppies, ornamental kale and cabbage |
| Half-hardy annual flowers | Tolerate cool soils but not frosts | Can plant outside 2 weeks before average last spring frost date | Geranium, dianthus, lobelia, ageratum, petunias, gazanias |
| Tender annual flowers | Need warm soil and don’t tolerate frosts | Wait to plant outside 1-several weeks past last average spring frost | Zinnia, salvia, begonia, coleus, vinca, impatiens |
| Perennials | Check hardiness ratings and pair with your hardiness zone |
** Cool season annuals may decline in summer heat.
HARDINESS OF VEGETABLE CROPS
| Cool-season hardy annual vegetables* | Can tolerate 24-28 degrees F | Corn salad, arugula, spinach, broccoli, Chinese cabbage, kale, kohlrabi, turnip, parsnip, salsify, brussel sprouts, fava beans, leeks, garlic, some onions |
| Cool-season semi-hardy annual vegetables* | Can tolerate 28-32 degrees F | Beets, carrots, cauliflower, lettuce, onion, peas, radishes, spinach, Swiss chard, endive, radicchio, kale, mustards |
| Warm-season annual vegetables that do not tolerate frost | Cannot tolerate temperatures <32 | Beans, corn, peppers, eggplants, melons, pumpkins**, winter squash**, tomatoes***, melons***, pumpkins*** |
| Warm-season annual vegetables that do not tolerate frost | <50 degrees F decreases quality | Sweet potatoes, basil |
** Can withstand some light frosts if followed by warm day temperatures
*** Ripen further after harvesting when semi-ripe.
This Informational Sheet was compiled by Yvette Henson, Extension Director and Agriculture, Natural Resources and Horticulture Agent for San Miguel Basin. For other Fact Sheets or information on growing ‘High and Dry’ (at high altitude with water limitations) come by our office at 1120 Summit Street (across from the Fairgrounds) in Norwood, call (970) 327-4393, email Yvette.Henson@colostate.edu or maryw@sanmiguelcountyco.gov or visit our website at http://sanmiguel.extension.colostate.edu/
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