Any minute now, tulips will peek through the soil in enviable gardens across metro Denver. Bummer if you missed the window to plant bulbs.
The optimum time to plant bulbs in the Denver area is mid-September to late October when average soil temps are 55 degrees, according to the Denver Botanic Gardens. The bulbs need to establish roots before the ground freezes.
Growing zones across Colorado vary between hardiness zones 3 to 7, according to the U.S. Department of Agriculture. Tulips (Tulipa spp.) require 16 to 18 weeks of underground cold to flower. Cool temps stimulate a biochemical response inducing the flower to develop and bloom.
Once you purchase your bulbs, store them in the refrigerator at 35 to 45 degrees until planting time.
Prepare the soil by mixing 0-46-0 phosphorus fertilizer 3 to 4 inches below planting depth at a ratio of ½ pound per 100 square feet. Plant tulip bulbs with the tip upward at a depth four times the height of the bulb. Space the bulbs 4 to 6 inches apart. Water well. Mulch with 3 inches of organic mulch—chopped leaves, straw, grass clippings, compost, wood chips, shredded bark, sawdust, or pine needles.
Once planted, do not water the bulbs again until spring.
Here’s a tip: Mark your calendar now for Labor Day to buy your bulbs. Follow the instructions above and you’ll enjoy a lush bed of tulips under the arbor of the trees in your yard in Spring ‘23. And be sure to contact Donovan Arborists for your tree maintenance so that the trees are the perfect backdrop to the spring floral.