I live in Scarborough and have been reading a great deal from US sources about winter sowing for flowers such as bachelor buttons, alyssum, cosmos, etc. The hardiness zones of the writers seem to be comparable to ours in Toronto. Is this practice possible for some of our hardier flowers? I hear these plants can be more robust than those started inside.
Thank you for any advice!
Thank you for your question.
Since the flowers you mention as examples are all annuals which naturally re-seed themselves, even in Toronto, planting some seed now should not do any harm. (I’m assuming that you are not referring to using any kind of container.) As the ground and snow-cover freeze and thaw repeatedly the seeds will work their way down into the soil. (It might be interesting to plant some now, and some after frosts are over, and then compare the results.) Perennial wild flower seeds often require a cold period (pre-chilling) in order to germinate.
Of course, every flower is slightly different, and exact conditions have a bearing on the local micro-climate. For instance the Missouri Botanical Garden website (a reliable source for accurate information) says regarding bachelor’s buttons (Centaurea cyanus) that you can plant outside in the fall “in milder winter climates”. This describes protected, sunnier spots in Toronto sometimes, but not every winter. I haven’t planted alyssum for many years; it re-seeds itself copiously and I just weed it out where I don’t want it.
There are a couple of general things to beware of when you try this: if the soil is not completely frozen, avoid standing in the flower bed and compacting the soil; and mark where you put your seeds so that you do not weed the seedlings out later!
The Toronto Master Gardeners website archive link below is an article on sowing vegetables in the winter, but you may find some of the other links cited there useful as well.
Good luck with this interesting experiment!
February 14, 2021