Discover the Best Time to Plant Wildflower Seeds in Colorado

Wildflowers bring an element of natural beauty to any garden, offering a vibrant and ever-changing palette of colors. Contrary to popular belief, the term “wildflower” does not exclusively refer to native flowers. It characterizes the overall look and feel of an informal planting, incorporating a mix of native and non-native species.

The Delight of Wildflowers

A wildflower planting provides a captivating display throughout the growing season, with different plants blooming at various times. This natural diversity adds charm and interest to the garden, but it’s important to note that some wildflowers can be aggressive and may eventually outcompete other species. Furthermore, specific site conditions can exacerbate their invasive tendencies. It’s crucial to be aware of such factors to maintain a healthy balance in your garden.

Choosing the Perfect Seed Mix

Selecting the right seed mix is crucial to achieving the desired effect in your wildflower garden. Consider your site conditions and the visual impact you wish to create. You can model your wildflower plantings after native-plant communities or use them to create bold splashes of color. Commercial seed mixes are formulated with a variety of plants, offering diverse heights, colors, and bloom times.

For optimal results and a prolonged blooming season, opt for a mix that includes self-seeding annuals, biennials, and perennials. Additionally, some seed mixes include grass species, which provide texture, color contrast, and support to the wildflowers. Grasses also help control soil erosion and enhance wildlife habitat.

Site Preparation and Weed Control

Before planting wildflowers, proper site preparation is crucial, especially if the soil is poor, compacted, or overrun with weeds. Lightly cultivate the soil or use a rake to break it up before sowing the seeds. If the soil is compacted or clay-like, incorporate organic matter like compost or sphagnum peat moss to a depth of 6 inches. A recommended amount is about three cubic yards of organic matter per 1,000 square feet.

Weed control is essential prior to planting wildflowers to prevent them from competing with your desired plants later on. Water the area to germinate any existing weed seeds, then eliminate the weed seedlings by pulling, hoeing, or using an appropriate herbicide. Repeat this process as necessary until the area is free of weeds.

Sowing Your Wildflower Seeds

For successful seed germination, mid to late fall is an ideal time to sow wildflower seeds in Colorado. The subsequent winter cold and snow provide the necessary moisture for germination in the following spring. If you prefer sowing in spring or summer, check with the seed company to see if they have pre-treated (stratified) perennial seeds.

Ensure adequate watering in the spring or summer if winter moisture is insufficient for seed germination. Follow the recommended seeding rate indicated on the seed packet to avoid poor stands. For an even distribution of wildflower seeds, mix six parts dry sand with one part seed.

Spread the seed mix by hand and lightly rake it into the soil. Afterward, tamp the soil gently with your feet to ensure good seed contact. For larger areas, use a cyclone-type fertilizer/seed spreader followed by pulling a section of chain-link fence behind a tractor. Another option is hydro-seeding, which works well for extensive areas.

Maintenance Tips for a Thriving Wildflower Garden

Once your wildflowers have established themselves, it’s essential to control weeds and provide supplemental water during extended dry spells. Fortunately, if you’ve prepared the soil properly, little to no fertilizer is required. In case you need to fertilize, opt for a mild, balanced fertilizer.

After the plants have been affected by a killing frost and have browned, mow the wildflower areas to distribute the seeds set by the plants. Cut stalks to a height of 4 to 6 inches and leave the clippings on the ground, or leave them in place throughout winter and trim back in the spring. The appearance of your wildflower garden may vary in the second and subsequent years due to the bloom of biennial and perennial species. Additional seeding can be beneficial if the stand isn’t satisfactory or if certain areas experienced poor growth.

Native Wildflowers, Grasses, and Noxious Weed Awareness

Here are some native wildflowers and grasses commonly found in seed mixes:

Plant Name	Type	Flower Color	Season of Bloom
Aster novae-angliae	P	Violet	F
Achillea millefolium	P	Blue	SU
Campanula carpatica	P	Blue	SU
Centaurea cyanus	A	Blue	SU
Clarkia unguiculata	A	Pink, lavender	SP/SU
Consolida ambigua (Delphinium consolida)	A	White, pink, violet, blue	SU
Coreopsis lanceolata	P	Yellow	SU
Cosmos bipinnatus	A	Pink, red, white	SU
Dianthus barbatus	B/P	Pink, red, white	SU
Dimorphotheca aurantiaca	A	White, orange	SU/F
Echinacea angustifolia	P	Pink	SU
Echinacea purpurea	P	Purple	SU
Eschscholzia californica	TP	Yellow/orange	SP/SU
Gaillardia pulchella	A	Yellow/red	SU
Gypsophila elegans	A	White	SU
Iberis umbellata	A	Pink, white	SU
Leucanthemum x superbum (Chrysanthemum x superbum)	P	White	SU
Linaria maroccana	A	Pink, yellow, violet	SP/SU
Linum grandiflorum rubrum	A	Scarlet	SU
Linum perenne	P	Blue	SP/SU
Lobularia maritima	TP	White, lavender	SP/SU
Lupinus spp.	A/P	Blue, pink, red	SP/SU
Myosotis sylvatica	A	Blue	SP/SU
Oenothera missouriensis	P	Yellow	SU
Papaver rhoeas	A	White, pink, red	SU
Phacelia campanularia	A	Blue	SP/SU
Silene armeria	A/B	Pink	SU
Solidago rigida	P	Gold	SU/F
Viola spp.	P	Purple/yellow	SP/SU/F

Avoid seed mixes containing noxious weeds such as Cichorium intybus (Chichory), Hesperis matronalis (Dames’ rocket), Leucanthemum vulgare (Oxeye daisy), and Linaria vulgaris (Yellow toadflax).

For more information on creating stunning wildflower gardens and navigating Colorado’s unique climate, visit the Ames Farm Center.

J.E. Klett, a horticulture specialist and professor at Colorado State University Extension, along with R.A. Cox, I. Shonle, and L.G. Vickerman, have contributed their expertise to the development of this fact sheet.