WINTER PLANNING TOOL
Can I Start Seeds Yet?
Pick your city. Every indoor sowing window is dated from that city’s own last spring frost, so the answer in Vancouver is not the answer in Winnipeg — and in December it is genuinely different.
Can I start seeds indoors yet in Canada?
It depends on your city, and the spread is about ten weeks. Indoor sowing is counted backwards from the last spring frost, so the first windows — onions and leeks, twelve weeks ahead — open in late December on the BC coast, late January in southern Ontario, and not until early March on the Prairies. Everything else follows from there.
Pick a city above to see which seeds you can start today.
Meanwhile — what you can plant indoors today
None of the above depends on the weather, so all three work in any city, in any week of the winter. They are also the reason a January windowsill is worth keeping.
🌱 Microgreens
Sown thickly in a shallow tray and cut at the first true leaves, usually 10–14 days. Radish, pea and sunflower are the fastest. No grow light needed if you have a bright window, though they stretch without one.
🫙 Sprouts
A jar, a rinse twice a day, and no light or soil at all — ready in 3–6 days. The one genuinely weather-proof crop, and the only thing on this page that works in a basement.
🌿 Windowsill herbs
Basil, parsley, chives and mint carry on all winter indoors, but a Canadian December window gives them under nine hours of daylight. Expect slow growth, and add a small light if the stems stretch.
How this works
Every window is your city’s last spring frost minus the crop’s head start — onions twelve weeks, tomatoes six, cucumbers three — and stays open for a fortnight after that. The frost date is Environment and Climate Change Canada’s climate normal for a named station near you. The head starts and the fortnight are conventional Canadian practice, not measurements, and they match what our seed-starting calculator and growing guides already say.
In December and January the tool counts to NEXT spring’s frost date, which is what a gardener means by “last frost” at that time of year. Sowing much earlier than the window does not buy you an earlier harvest: seedlings held too long indoors get leggy and root-bound, and transplant worse than younger ones sown on time.
Frequently asked questions
Is it too early to start seeds in January?
For most crops in most of Canada, yes — but not for all of them, and that is the point of checking your own city. Onions, leeks, celery and artichokes need ten to twelve weeks indoors, so their windows open in late December on the BC coast, late January around Toronto and Windsor, and early March in Winnipeg or Edmonton. Tomatoes, peppers and brassicas are six to eight weeks and belong to late February or March almost everywhere. Starting a tomato in January gives you a tall, pale, root-bound plant by May, not an early crop.
What happens if I sow earlier than the window?
The seedling outgrows its light and its pot before the ground is ready for it. Indoor light in a Canadian winter is far weaker than daylight, so an over-held seedling stretches, thins and often flops; roots circle the pot and the plant sulks for weeks after transplanting. A tomato sown on time in March routinely overtakes one sown in January. If you have already sown early, pot up into a larger container and get the plant under a strong light rather than trying to hold it back.
Do I need a grow light to start seeds indoors in Canada?
For anything you intend to plant out, effectively yes. A south window in February gives roughly nine to ten hours of weak, low-angle light, and seedlings respond by stretching towards it. A cheap full-spectrum LED a few inches above the tray, run 14–16 hours a day, is the single biggest difference between stocky transplants and leggy ones. Microgreens and sprouts are the exception — you harvest them before light becomes the limiting factor.
Why does the date change so much between cities?
Because the whole schedule is anchored to the last spring frost, and Canada’s spread is enormous. Victoria and Vancouver are frost-free by mid-March; Winnipeg and Edmonton are not until late May; northern communities later still. That is a ten-week difference in when the same crop should be sown, which is exactly what generic advice written for a US zone map gets wrong here.
Can I still start seeds if the window has closed?
Often, yes, with a smaller plant as the cost. A window closing is not a wall — a tomato sown two weeks late simply goes out smaller and fruits a little later. The crops that genuinely punish lateness are the long, slow ones: onions, leeks and celery started a month behind rarely size up before the season ends. For those, buying transplants is a better answer than sowing late.