Our garden is essentially a cottage garden. This is a less formal garden that has a sense of naturalness. Mostly, I let flowers bloom where they like. I only pull them if they are blocking a water emitter, if a tall flower is too near the front of the border, or if a bed is being overrun by a less desirable variety. When choosing wildflowers, I don’t just pick ones native to Colorado. I look for appropriate USAD zones (zone 3 and sometimes 4) and elevation information, if available (needs to thrive up to 7,543 feet).
Late fall, after a couple of good freezes, is a good time to plant wildflower seeds in our environment. Why plant in the fall? I try to plant after the ground has cooled, but before any big snowfall. This gives the seeds to remain dormant over the winter and gives them a chance to germinate in the spring when conditions are appropriate.
Some seeds actually require cold periods in order to germinate. I’ve had some seeds that come with instructions to place in the freezer for a time if your weather isn’t cold enough or if you’ve waited until late spring to plant. Also, giving the flowers a head start can cut down on the number of weeds that spring up.
How do you know when to plant? You want the soil cool enough, so the seeds don’t sprout in the fall. For me in our Alamosa garden, it means waiting until we’ve had some nights with temperatures well below 32 deg. F for several hours. I try to time the planting when the top inch or so of soil is still loose so I can gently cover seeds that don’t like to be on the surface.
Where should you plant? Most wildflowers prefer at least six hours of sun per day starting in the early spring. The rule of thumb is the more sun, the better for wildflowers according to David Salzman of HighCountryGardens.com (HCG).
How should the soil be prepared? Make sure to remove all weeds and cut back any perennials in the area. Pull any previous annual stalks. Wildflowers do best in well-drained and aerated soil. Make sure soil is not compacted by digging with a trowel or shovel. If the soil is too compact, roots won’t be able to easily spread. I tend to work in some mulch and/or soil conditioner each year.
How to distribute seeds? I tend to mix the seed with some sand before strewing. HCG recommends mixing 10 parts sand to 1 part seed. For the sand I just use some of the native ground outside our fence -- local winds do a great job of bringing in a bit of new sand each year!
I then strew the seeds in the planting area and walk over them to compress them into the soil. This can be tricky as some seeds need sunlight to germinate so you don’t want the sand to cover them. On the other hand, we have a lot of wind over the winter so I don’t want the seeds to blow away. I also tend to cover them with a light layer of loose mulch from cut up plant stalks to help keep them in place while allowing sunlight to filter in. I always hope that enough seeds meet the right conditions to germinate in the spring. I definitely do not water them in late fall. I don’t want to take the chance they might germinate on an unusually warm day.
Springtime follow-up: I long for early spring growth so walk the garden starting in March. This year we had plenty of early moisture so I didn’t need to water, but it was also cool enough that most of the flowers came up a bit later than usual. Just the opposite happened in 2018. We had such a dry and warm winter that I started watering in March. Many wildflowers take between two to three weeks to germinate.
According to thespruce.com, often seeds that self-sow require light to germinate. Also most are smaller seeds. Frequently listed are columbine (Aquilegia), blanket flower (Gaillardia), bellflower (Campanulaceae), balloon flower (Platycodon gradiflorus), and poppies (Papaver and Eschscholzia).
“I think I like wildflowers best. They just grow wherever they want. No one has to plant them. And then their seeds blow in the wind and they find a new place to grow.” Richelle in “What If” by Rebecca Donovan