July 2025 Newsletter
Happy Canada Day! In this month’s newsletter we are looking at the success of four methods for growing native plants from seed: cold moist stratification in the fridge, winter sowing, seed balls and direct sowing in the fall.
Cold moist stratification in the fridge
This is one of the two main ways that I grow native plants. The process started in early December by putting seeds in the fridge (details and photos are in the March newsletter). In early February the seeds came out of the fridge and were planted into small pots. In March the tiny seedlings were transplanted into flats. The flats stayed indoors under lights until mid April when they were transferred to my unheated greenhouse. In early May I started planting the plugs in the ground. By the end of June they were all planted in their seed production beds.
This method works great for most species, although it is labour intensive, and you need indoor space and lights. There are a few species that either don’t germinate or don’t grow well indoors: the milkweeds (Asclepias sp.), the sunflowers (Helianthus sp.), elderberries (Sambucus sp.), Showy tick trefoil (Desmodium canadense), Round headed bush clover (Lespedeza capitata), Blue flag iris (Iris versicolor) and Canada Anemone (Anemonastrum canadense). Those species grow better when they are winter sown.
Winter Sowing
This is the second main way that I grow native plants. The winter sowing boxes were set up in early December. I placed them where there would be a large snowbank in the winter, they stayed there until the snow melted. The boxes were moved into the unheated greenhouse in early April. When the seedlings were large enough I transplanted them into flats (for more information see the April newsletter).
They are currently still in their flats and I have moved them out of the greenhouse and into a shady location. I waited too long to plant them into flats and that has delayed them growing to a large enough size to be planted into the ground. Lesson learned for next year!
The milkweeds, sunflowers, elderberries, showy-tick trefoil, round-headed bush clover and Canada anemone do really well when they are winter sown. Great germination with strong seedlings. I suspect that they like to be frozen and also enjoy the temperature swings that winter sowing provides that is absent from the fridge method.
I am a big fan of winter sowing. I’m still sorting out the timing of transplanting and planting the seedlings, but this is a fantastic way to grow native plants.
Direct seeding into pots
Most grass species (and some wildflowers) don’t need to experience cold in order to germinate. They don’t need to be winter sown or to go in the fridge. I tend to sow them into pots in early February at the same time as I am taking my seeds out of the fridge.
Direct seeding trials
This year I ran two trials with direct seeding, one using seed balls and the other with sprinkling a little bit of seed on top of the soil. I used scrap pieces of fencing to act as a grid. Each square in the grid contains a different species, there were over 75 different species in the trial. There were two grids, about 10 feet apart in the same section of the garden, one grid for seed balls and the other for direct sowing.
I ran the experiment on a section of ground with good, weed free soil in full sun. Results would differ based on the type of soil, weed competition and the presence of insects and/or animals that might eat the seeds or seedlings.
Seed Balls
I was excited to experiment with seed balls this year. It is a popular technique with guerilla gardening and a fun activity to do with kids. In early December I made seed balls of all the different species that I am working with and placed them on the surface of the soil in the garden. (For more information on how I made the seed balls, see the January newsletter.)
While some of them grew well using this technique, I found that they grew better with direct seeding. The seed ball concentrates a clump of seeds in a very small area, and they end up competing with themselves. Or the seeds struggled to fight their way through the clay of the seed ball once they germinated. It wasn’t worth the extra effort needed to make the seed balls.
This is the one technique that I will not do again next year.
Direct Seeding in garden beds
This technique worked better than the seed balls. The seeds were still scattered in a small area, but the seedlings had more room to grow. The asters, goldenrods and sedges did particularly well with direct seeding. I thought I was going to lose a lot of seeds to mice and other creatures eating them, but that did not happen.
I did notice that insects were eating the tiny seedlings when they were young, which doesn’t happen with my plants grown in flats.
I will be doing a lot more direct seeding next year.
Conclusions
Next year I will still use three different methods (fridge, winter sowing, direct seeding) for germinating my seeds because it allows me to stagger my production and produce more plants. I am starting to refine which method to use with each species, since there is a collection of species that do significantly better when winter sown than when I put them in the fridge. I will be doing a lot more work with direct seeding next year, so stay tuned for more adventures growing native plants from seed!
The online shop will be closed for the first two weeks of July while we are preparing some new species and working on inventory. New species that will be available later in July: Mitrewort (Mitella diphylla), Long-stalked sedge (Carex pedunculata), Golden sedge (Carex aurea), Peck’s sedge (Carex peckii) and very limited amounts of Prairie Smoke (Geum triflorum).
Take some time to stop and enjoy your native plants this month!
Andrea D’Silva
Swallowtail Native Plants