Get Ready to Sow Some Seeds!

 Posted by: Deryn Davidson, Horticulture Agent, Boulder County

Photo from CSU Extension Fact Sheet 7.233

Native wildflower and grass seeds can be sown any time of year, but we are entering the ideal sowing window: Fall. Whether you are looking to covert a small section of your yard to a more naturalized looking pollinator garden, or your HOA is considering creating large areas of native vegetation, as the cooler weather approaches, you can be planning out your steps.

Seed sourcing: There are many wildflower mixes available both in retail and online spaces. Buyers beware, some of the species that might be included in those mixes are often non-native and invasive. They can quickly become more of an issue than a benefit. Be sure to look closely at the species list and try to source your seeds from local, reputable sources rather than more generic, national level brands. What might work well in the one part of the county, could be a problem here in the intermountain-west. Which wildflower mix you choose will depend on your location and site. Just like if you’re planting live plants from the nursery, you want to make sure that you choose appropriate species for your soil type, exposure (sun vs. shade), elevation, and moisture levels (what you’re willing to provide or based on site conditions).

Site preparation: Site preparation is typically necessary to get the space ready for seeding. In some areas   this is minimal, in other areas you made need a full year. If you’re removing turf, that needs to be done ahead of time. If you have an open area of soil, weed control needs to be done before sowing so that next spring the seedlings don’t have to compete with established weeds. If your soil is compacted or low quality, you’ll want to add organic matter into the top 6-inches to make the seed bed more hospitable. If you till it in, you will bring weed seeds to the surface. While this sounds like a bad thing, you can use it to your advantage. If you start prepping soon enough in the season, you can water the area and allow those seeds to germinate. Then you can come in and weed those out. Preparations may take more time in areas where the number of weed seeds is high or if you have more difficult to remove species like Canada thistle or bindweed.

Seeding: Fall is a great time to seed most species that will come in a native wildflower seed mix. Ensuring good “seed to soil” contact is important. By that we mean making sure that each seed is touching the soil and typically has a thin layer over it. You can accomplish this by putting your seed out at the proper rate and then lightly raking over it. Then tamp the soil with your feet by gently walking on it to make sure that contact is happening. Purchased seed should come with a recommended “seeding rate”, or the number of seeds to sow per area of ground. For example, the recommendation might be 5-pounds per acre if you’re doing a large area, or 1-ounce per 100-square feet for smaller areas. If you’re seeding larger areas, the rake and tamping by walking method might not be realistic. In those instances, you’ll want to investigate mechanical seed spreaders and larger options for achieving the seed to soil contact like a sod roller. The moisture that we (hopefully) receive over the coming winter months will allow for germination the following spring. If we don’t get much moisture over the winter, be sure to water the area in the spring and keep it moist (not soggy wet) until you start to see seedlings emerge.

For more information including a plant list, check out Fact Sheet No. 7.233 https://extension.colostate.edu/topic-areas/yard-garden/wildflowers-in-colorado-7-233/