Every spring in Colorado, the “Is it safe yet?” question comes up—and every spring brings a different answer. Springtime has always been variable, and as the climate changes, so does the safe planting date.
But here are some questions you can ask yourself to determine when the time is right: Has the snow melted? Is the ground dried out enough that you can walk across your property without sinking in? Working in wet soil is never a good idea since you can compact it, reducing its ability to transfer water and nutrients to the plant roots. If you can form a soil ball that sticks together when you handle it, it is too wet to work.
Once the ground is workable, get the weeds out! Spring cleaning in the garden is time-consuming, but so important. Rake up the leaves and any fallen twigs or branches. Tidy up your perennials; they are often happy to spread, and they may want to take over an area. Don’t be afraid to dig them up, divide or compost the extras and then replant them. The smaller the perennial, the easier it is to move it, so do this early in the spring before they start a growth spurt.
It is also a good idea to add compost early in the spring because the coming rain will help to leach nutrients down from the compost into the plant roots.
As soon as the ground is workable in the spring—as soon as you see flowers peaking up out of the ground—it is safe to plant new perennials. Perennials are adapted to cold nights but those coming right out of a greenhouse are tender and could freeze at temperatures below 30 degrees. It is best to buy plants that have been outside all winter or for a few weeks, not in the greenhouse. It is a good idea to ask about this when purchasing plants in the early spring.
At Dwyer Greens & Flowers, we purchase young liners and bare root perennials in late February and early March and then grow them in the greenhouse for four to six weeks, giving them a chance to root into their containers. Then we kick them outside to “harden off” in an unheated, protected area. If you purchase perennials that have not been hardened off it may be necessary to set them in a protected area for a week or two. This can be under an eave or any other roof or covering. If you use cloth for protection, be careful as the cloth must not touch the plants. Once they are hardened off, they will withstand the cold.
Annuals are another matter. They should not be planted until the weather “settles”, and some annuals are hardier than others. Pansies like it cool and once they are hardened off, they are fine in temperatures as low as 25 degrees. Other annuals—zinnias, marigolds, basil and tomatoes—won’t withstand anything below 32; they really need warmer nights.
In the lower Roaring Fork Valley, it is usually safe to set hanging baskets and other annuals out around mid-May. But I caution everyone to watch the weather as it may be necessary to protect them some nights. (You can see month-long forecasts for individual towns online at AccuWeather.com)
Safe planting dates vary by elevation, and at Dwyer Greens, we never deliver pots or plant annuals at higher elevations until mid-June.
Average Safe Planting Dates for the Valley
- Rifle, New Castle – May 15
- Glenwood Springs – May 30
- Carbondale, El Jebel, Basalt – June 1
- Snowmass, Aspen – June 15
Author Lynn Dwyer, co-owner of Dwyer Greens & Flowers, teaches classes and workshops and mentors gardeners. Learn more at DwyerGreens.com.