Beets are a cool-season root vegetable, but achieving a successful harvest depends on precise timing within Colorado’s varied climates. The state’s vast topographical differences mean a single planting date is impossible, as the window for direct sowing shifts dramatically based on local weather patterns and elevation. Successful beet cultivation requires attention to two primary factors: local frost dates and the specific temperature of the soil, which determines when the ground is ready for germination and root development.
Understanding Colorado’s Growing Seasons
Colorado’s geography divides its gardening into three distinct regions, each with a unique growing calendar determined by its elevation. The warmest and longest seasons occur in the Front Range and Plains, which includes major cities like Denver and Fort Collins. These areas generally see their last spring frost around mid-May and their first fall frost in late September.
The Western Slope, encompassing areas like Grand Junction and Montrose, experiences a more variable but often milder winter, resulting in a growing season long enough to support multiple crop cycles. In contrast, the High Mountain and High Altitude areas, such as those near Aspen or Steamboat Springs, have the shortest and coolest seasons. Gardeners in these regions may not see their last frost until mid-June or even July, drastically condensing the planting window for all vegetables.
The fundamental trigger for planting beets is the temperature of the soil, not the calendar date. While seeds can germinate in soil as cold as 40°F, optimal sprouting occurs when the soil consistently reaches at least 50°F. This temperature determines the earliest possible moment for direct sowing.
Timing the Spring Planting
The earliest spring planting is timed so beet roots develop during mild temperatures before summer heat arrives. For the Front Range and Plains, the ground often becomes workable and reaches the 50°F soil temperature target by late March or early April. Planting can begin then and continue with succession plantings every two to three weeks until late May.
In the Western Slope valleys, the planting window typically opens a few weeks later, with gardeners often starting direct sowing in late April to early May. These regions can also support succession planting into early summer due to the extended growing season length. Gardeners in the High Mountain regions must wait significantly longer, often delaying planting until late May or even the first week of June.
The goal for the spring crop is to ensure the roots mature during the cooler early summer when temperatures do not consistently exceed 75°F to 80°F. Higher temperatures can cause the beetroots to become tough, woody, or develop internal white rings, impacting their quality. Planting a fast-maturing variety, which typically takes 50 to 60 days, allows for a harvest before the intense summer heat sets in.
Timing the Fall Planting
To achieve a second, late-season crop, timing is calculated by counting backward from the region’s average first fall frost date. This provides the latest possible date for direct sowing, ensuring beets reach maturity before a killing freeze. The calculation requires allowing for the beet’s days-to-maturity (averaging 50 to 70 days), plus an additional buffer of 10 to 14 days for slower germination in mid-summer soil.
For example, in the Front Range where the first frost generally occurs around September 20th, counting back 70 days plus the two-week buffer suggests a planting window from mid-July to early August. This timing allows the roots to swell during the cooling temperatures of late summer and early fall, which enhances the beet’s natural sweetness. Planting beets for a fall harvest is not feasible in the shortest High Mountain growing seasons, where the first frost can arrive as early as mid-August.
Essential Care Immediately After Sowing
Once the seeds are sown, consistent moisture in the upper soil layer is necessary for proper germination. Beet seeds are unique because they are multi-germ seeds, meaning a single cluster contains between two and five true seeds. When a cluster sprouts, multiple seedlings emerge in the same spot, requiring immediate and deliberate thinning.
Thinning is necessary to prevent overcrowding, which results in small, malformed, or underdeveloped roots due to competition for light and nutrients. When seedlings develop their first set of true leaves, gently snip all but the strongest seedling at the soil line using small scissors. Pulling unwanted seedlings is not advised, as it can disturb the delicate roots of the remaining plant. The initial thinning should leave plants spaced three to four inches apart to allow the beetroot to expand.