Ask Mr. Smarty Plants

Our first thought was that you can't get there from here.   In Jefferson Co., Colorado you are at USDA Hardiness Zones 4a to 5b, pretty cold for Hesperaloe parviflora (Red yucca), which is native to southwest Texas and northern Mexico. However, we did some more research and learned that this plant can tolerate temperatures down to zero, and likes rocky mountainsides. Read more about it at The Laptop Gardener "Tough as Nails" Red Yucca. We would caution you about using seeds you gathered somewhere else. If you found Red Yuccas growing near you and gathered seeds from those, the plants you propagate have a much better chance for survival.

From Jill Nokes' book How to Grow Native Plants of Texas and the Southwest (see Bibliography below) we found these instructions for propagation of Red Yucca:

"Coral Yucca sprouts readily from untreated seed. Sow the seed immediately after harvesting in seed flats, or in individual 4- or 6- inch pots. The container should be at least 4 inches deep and contain well-drained soil media. Plant cells tend to cramp the roots, causing them to grow in knots. Premoisten the soil and then gently press the seed into it, without watering. Keep in a cold frame until the following spring. Some seed will sprout immediately, while others will continue to emerge over the course of the season. Some growers leave this plant in a flat for a year before moving it into a one-gallon container. After 6 months, move it to strong sunlight."

From our Native Plant Imsge Gallery:

Hesperaloe parviflora

Hesperaloe parviflora

Hesperaloe parviflora

Hesperaloe parviflora