Some flowers need a period of cold stratification in order to germinate come springtime. And of the flowers that like a period of cold, wet weather, some of these prefer to be direct-sown (like Poppies, Milkweed, and Butterfly Weed). Others don’t require direct sowing, but it sure makes things easier (no need for growing mediums, fancy equipment, or space in the refrigerator).
Mainly, you’ll need a patch of well-drained, weed-free soil and plant markers to remind you to keep a lookout for seedlings come springtime. Over-sow by about 20% if you want to account for run-off and nibbling critters. Water once and let seasonal precipitation and low temps do their magic until spring.
Here are some of our favorite varieties to winter sow.
Milkweed (Asclepias syriaca) and Butterfly Weed (Asclepias tuberosa) both need cold stratification in order to germinate, making winter the perfect time to sow a butterfly sanctuary. Monarchs and other butterflies rely on Asclepias for nourishment and habitat. Learn more about sowing Milkweed here.
Poppies are extraordinarily beautiful but you will be hard-pressed to find poppy seedlings at your local nursery in spring. This is because most poppies do not transplant well and prefer to be direct-sown into the garden. The good news is that poppies are very easy to grow, even in poorer soils. Read more about growing poppies here.
Self-sowing annuals like Johnny Jump-Ups, Chamomile, and Spider Flower will readily tough out the cold. If the winter is not overly harsh, Calendula, Borage, and Marigolds will also do quite well.
Many flowering perennials require an extended period of cold in order to germinate. Campfire Rudbeckia, Echinacea, Columbine, and Yarrow can all be winter-sown. Try Blazing Star or Anise Hyssop for vertical interest.
If you are not exactly sure where you want your winter-sown plants to grow, or otherwise prefer a little more control over the germination process, you can sow your seeds in plastic containers and leave them outside. Cold-hardy and semi-cold-hardy seeds can be sown in light-permeable plastic containers and left (partially covered) outdoors; find more details on this technique here. This approach allows added protection from really low temps, run-off, and critters and helps you keep track of what you’ve sown.