Season extenders: Growing season isn’t over yet


Given that the frost-free dates with 50 percent probability are June 22 and Sept. 7, the average outdoor growing season in the Pagosa Springs area is a short 77 days. A short growing season, combined with windy conditions, cool mountain nights, resident herbivores and occasionally limited water availability, make gardening in Pagosa Country challenging. Careful planning and determination can help you to successfully grow a bountiful garden and enjoy produce and flowers longer into the fall season.

One of the most important things to consider when planning a garden is plant selection. When you choose the right plant to put in the right place, chances of successful production increase greatly. A short growing season and cool nights means that, generally, it doesn’t stay warm enough for long enough in an outdoor garden to support coveted warm-season crops like cucumbers, peppers, beans and tomatoes. Instead, cool-season vegetables, including leafy greens and root crops, are more productive and easier to grow.

When looking for vegetables and varieties to try in the outdoor garden, select those that thrive in cooler climates and mature for harvest in fewer days. Keep in mind that even short-season plants will need extra days to mature in cool, high-altitude climates. When selecting annual vegetables and herbs, focus on varieties that require fewer days to mature and also those that are frost tolerant. If you are selecting perennials, look for those that are winter hardy as they will live through the winter and regrow the following season.

Ways to get the most out of short-season crops and to even encourage longer-season crops to mature quickly include transplanting in the spring if appropriate, managing fertility properly and watering adequately. Transplanting allows plants to complete part of their life cycle indoors so they have a head start when they are moved outside. Managing fertility means avoiding over-fertilization of annual plants so they set fruit and complete their life cycle more efficiently. Adequate irrigation in the spring and summer allows for expedient plant development. If you are interested in growing longer-season varieties or experimenting with warm-weather crops, season extension techniques will be a key component of garden management and planning.

“Season extender” is a general term used to refer to any technique or product that protects plants from untimely frosts. Untimely frosts are generally radiation frosts that occur on clear nights in the absence of insulating cloud cover. Radiation frosts generally occur in the spring and fall and only bring temperatures down a few degrees below freezing levels, making it worthwhile to protect your garden. Season-extension products and techniques may also hasten plant growth by trapping heat, providing a warmer environment for continued plant growth.

Season extenders protect plants so they can continue to grow and mature in times of variable frost. They are especially important tools in dry, continental climates, like that of Pagosa, where daytime and nighttime temperatures can vary significantly. Ultimately, a season-extension product or technique is any structure or situation that insulates plants by putting a barrier between them and the outside or holds heat to protect plants from frost.

One crucial consideration in planning and managing a garden in a high altitude area is microclimate. As a general rule, temperatures drop about 3.5 degrees per every 1,000 feet in elevation gain, so higher elevations are commonly cooler later in the spring and earlier in the fall.

Taking advantage of and strategically creating warm microclimates, however, can be a useful season-extension technique. When choosing planting spots outdoors, consider shade, wind protection and the warmth of the specific planting area; places near brick, rock, homes, fences and areas with good southern exposure generally absorb and retain heat from the sun, creating a warm microclimate.

Topography also plays a role as sloped areas, especially south-facing slopes, stay much warmer than valley areas when cool air sinks at night. One of the most popular season-extension techniques is constructing and planting in raised-bed gardens. A raised-bed garden creates a small microclimate in which soils warm up more quickly in the spring, thereby extending the growing season earlier into the year.

Popular spring season extension techniques include using plastic mulch to warm the soil, cloches, water covers, floating row covers, low tunnels and even sheets or blankets to cover tender plants. Cold frames and starting plants indoors also helps gardeners to get a jump-start on the growing season. Season extension into the fall can be a bit trickier than season extension in the spring as plants have been outside all summer, growing larger and larger, making it more difficult to put up a barrier between them and cold, frosty air. The most reliable way to extend the growing season into the fall is to cover tender vegetation and fruits.

One of the simplest ways to extend the growing season into the fall is to cover plants with blankets, tarps, floating row cover or frost cloths to trap heat from the day, as well as to keep nighttime cold away. Cloth protectors have to be removed each morning and replaced each night so that plants can continue to grow and so that soil warms when the sun is out. Using blankets and sheets is an effective way to protect plants from radiation frosts as long as the fabrics remain dry, so throw those extra sets on your garden on cold, dry nights, but remember to take them off in the morning. Floating row covers are a good alternative to sheets and blankets as the lightweight material transmits light so it doesn’t have to be removed during the day. Row covers can rest directly on plants or be suspended by a low frame; they generally provide 2-4 degrees of frost protection. In addition to insulating plants, row covers can also be used to protect from wind, screen insects and deter hungry herbivores.

More sophisticated season-extension techniques and products can also be used to extend the growing season into the fall. Creating a low tunnel with a frame over the garden is another way to both keep the cold out and hold in warmth.

A low tunnel frame covered with clear agricultural plastic or row cover can also be used to protect plants from cooling wind and deter hungry herbivores. The low, spread-out shape of low tunnel covers makes them ideal for trapping radiant heat from soil, although the ends and side of these covers should be opened during the day to prevent overheating. On warm days, it is best to entirely remove the cover from its frame, whereas on cool days and warm nights the cover may be only cracked open. A low tunnel should be closed on cold nights and can remain closed on cloudy days. If managed properly, a low tunnel may provide 3-6 degrees of frost protection, and works well for cool-season crops that can tolerate light frosts. This technique may add between two and six weeks to the growing season in the fall or spring. Low tunnels become even more effective if another heat source or insulator is added to them, such as a space blanket, string of C-7 holiday lights, or even a small heater.

High tunnels, which provide greater air insulation, as well as greenhouse structures, are even more sophisticated methods of season extension that may allow a gardener to extend the season further into the fall, earlier in the spring and even allow for growth of plants that typically don’t grow well in Pagosa Country. These useful structures provide winter protection and trap heat, but need to be managed for cooling during the summer months and on warm days.

This article reviews a number of useful season extension techniques for the Pagosa Springs area and other high-altitude climates, although other techniques may also be used to effectively extend the growing season. More specific information about techniques mentioned here and about other techniques can be found by visiting or by contacting the Archuleta County Extension office at 264-5931.

Free wood chips

We are cleaning up the fairgrounds and all of the wood chips that helped keep things dry during the fair are available to anyone for pick-up. If you are interested, just bring your pickup and haul it away. No need to call the Extension office for permission.

CPR and first aid

CPR and first aid certification classes are offered monthly by the CSU Extension office on the second Monday and Wednesday of each month from 6-10 p.m. Anyone needing to receive or renew certification can register by calling the Extension office at 264-5931.

We will also schedule classes on additional dates with five or more registrations. Cost for the classes is $80 for combined CPR/first aid and $55 for individual CPR or first aid. The type of first aid information provided will vary by the needs of the audience. Group rates are available. Call the Extension office at 264-5931 for information.


Cutting fire wood this fall? Attend this free chainsaw safety class on Sept. 26 from 10 a.m. to noon at the CSU Extension building. Operating a chain saw can be dangerous. Whether you are out cutting firewood or pruning trees and shrubs, it is important to operate this important tool safely and maintain it for optimum efficiency. Learn techniques and safety tips from the experts at this workshop. No pre-registration is necessary, but for information, call the Extension office at 264-5931.

Shred-It event

Prevent identity theft — clean out your file cabinets and support the Archuleta County 4-H program by bringing up to three boxes of papers per person for on-site shredding on Thursday, Oct. 2.

The shred truck will be set up at the downtown Citizens Bank parking lot from 3 to 5 p.m. Cost is $5 per box and all proceeds go to support your local 4-H program.

No registration is necessary, but for questions, call the CSU Extension office at 264-5931.