Early emergence of bulb foliage is often seen on south or west exposures.Don’t worry too much if foliage has emerged early. Consider that the foliage is quite cold-hardy.
Snow is a great insulator and may protect hardy flowers from frosty temperatures. Tolerance to freezing temperatures depends on the plant. Spring bulbs, such as tulips, crocus and daffodils, tolerate a light frost or temperatures of 29 degrees Fahrenheit and above. You may need to cover bulbs on unusually cold nights when a hard frost occurs.
To prevent foliage from appearing too early, mulch bulbs in late fall with 2-3 inches of wood chips, bark, pine needles or other organic mulch materials. This added layer of mulch tends to keep the soil cooler and delays bulb foliage from emerging too early. Established bulbs benefit from mulches that are applied after the ground freezes.
A sandy-loam soil could also be added to a 1.5 to 2 inch depth to help protect foliage from early emergence. This added soil depth will delay emergence the following year. Use care to maintain the current grade around other landscape plants.
For more information, see the following Colorado State University Extension fact sheet(s).
For more information about bulbs, see the following Planttalk Colorado™ scripts.