Potatoes are a rewarding crop, but growing them successfully in Colorado requires a specific approach due to the state’s unique environmental conditions. The combination of high altitude and an arid climate presents distinct challenges compared to other potato-growing regions. Gardeners must adapt to temperature fluctuations and manage water efficiently to ensure a healthy yield. Understanding these climatic and soil factors is key to cultivating an abundant potato harvest.
Timing and Climate Considerations
Timing the planting correctly is the most important factor for a successful potato harvest in Colorado’s variable climate. Potatoes are a cool-season crop and tolerate light frost, allowing for early planting before the last expected spring freeze. In lower-elevation metropolitan areas, the average last frost is typically around the first week of May, allowing planting in early to mid-April.
Mountain communities and higher-altitude gardens may not see their last frost until mid-June, drastically shortening the growing window. For these areas, selecting early-maturing potato varieties ensures the tubers have enough time to size up before the fall freeze. Gardeners can pre-warm the soil by covering the planting area with clear plastic sheeting for a few weeks in early spring, raising the ground temperature above the 50°F minimum required for sprouting. Preparing the seed potatoes, a process called chitting or sprouting, is also recommended to gain a head start on the limited growing season at elevation.
Preparing the Soil and Planting
Colorado soil is often heavy clay with a naturally alkaline pH, which is not ideal for potatoes that prefer loose, slightly acidic soil. Before planting, thoroughly amend the garden bed by incorporating a generous amount of organic matter, such as well-rotted manure, peat moss, or compost. This addition breaks up dense clay particles, promoting the loose, well-draining environment potatoes need to expand.
If a soil test indicates a high alkaline pH, adding elemental sulfur or sphagnum peat moss helps shift the balance toward the slightly acidic range, discouraging common potato diseases like scab. Select certified disease-free seed potatoes for planting. Cut large potatoes into pieces, ensuring each piece has at least two viable “eyes.” Allow these cut pieces to cure for a day or two in a dry spot to form a protective callus, which prevents rot in the cool, moist spring soil.
The traditional planting method involves digging a trench approximately six inches deep and placing the seed potato pieces cut-side down, spaced about 10 to 12 inches apart. Initial cover should be a thin layer of soil, about three to four inches deep. This trenching method sets the stage for the process of hilling, which is performed as the potato plants begin to grow.
Ongoing Care and Regional Challenges
Maintaining potato plants in Colorado’s arid climate requires specific cultural practices, starting with the technique of hilling. Hilling involves gradually mounding soil, compost, or straw around the emerging stems of the potato plant as it grows. This is done repeatedly throughout the season until the final mound is a foot or more high.
Hilling serves two purposes: it prevents developing tubers from being exposed to sunlight, which causes them to turn green and produce solanine, and it encourages the stem to produce more potatoes higher up. Irrigation must be deep and infrequent to encourage strong, deep root development in a dry environment. Water thoroughly when the top two inches of soil feel dry, noting that the highest water demand occurs after the plants flower when tubers are rapidly forming.
A regional challenge is the Colorado Potato Beetle (Leptinotarsa decemlineata), which can quickly defoliate a crop. Organic management is the best defense, starting with annual crop rotation to disrupt the beetle’s life cycle. For small gardens, handpicking adults and their bright yellow egg clusters into soapy water is effective. Floating row covers installed early in the season can physically exclude the beetles, or an organic insecticide containing spinosad can be used as a targeted treatment against the larvae.
Harvesting and Storage
Determining the correct time to harvest potatoes for long-term storage is indicated by the natural die-back of the plant’s foliage. Once the plants begin to yellow and the vines start to collapse, stop watering entirely for about two weeks. This period of dry soil allows the potato skins to thicken and toughen, a process known as setting the skin, which is important for quality and extended storage life.
Harvesting must be done carefully to avoid skinning or bruising the tubers, which can lead to rot in storage. Use a garden fork to gently lift the entire plant and surrounding soil, working outward from the plant’s base to prevent piercing the potatoes. After harvest, the tubers need a short curing period to heal any minor injuries and further dry the skins.
Potatoes should be spread out in a single layer in a dark, well-ventilated location with a moderate temperature, ideally between 45°F and 60°F, and high humidity for seven to fourteen days. This curing process ensures the potatoes are prepared for winter. Long-term storage requires a dark, cool environment, with temperatures consistently maintained between 40°F and 46°F to prevent premature sprouting and shriveling.