BRITISH COLUMBIA — SEPTEMBER SOWING

Winter Salad Greens BC

Winter salad greens in BC are decided by one date — the day your city's light drops below ten hours — not by frost. Sow-by dates for 7 BC cities, worked out from latitude and this site's own crop data.

The Ten-Hour Rule — Why Frost Dates Are the Wrong Number Here

Below roughly ten hours of daylight, growth in the open effectively stops. Not slows — stops. A plant holds the size it has reached, stays alive, and waits. This is a light limit rather than a temperature one, which has two useful consequences: it arrives on the same date every year regardless of the weather, and it can be calculated exactly from latitude with no measurement and no guesswork.

For coastal BC that matters more than anywhere else in Canada, because the light runs out long before the cold does. Victoria's average first frost is December 15, but its day length falls below ten hours on November 1 — six weeks earlier. A gardener planning from the frost date has six weeks of growing season that does not exist. Vancouver, Nanaimo and Abbotsford all cross on October 31.

So a BC winter garden is a storage garden. Whatever size a plant reaches by late October is roughly the size it will be in January. You are not growing through winter; you are holding a standing crop outdoors and picking from it. That reframes the whole job: the only question that matters in September is whether a crop can reach usable size in the light that is left.

Day length computed from each city's latitude using the CBM solar model (Forsythe et al., Ecological Modelling 80, 1995). This is exact geometry, not an estimate. It says nothing about cloud, which coastal BC has plenty of — the figure is the ceiling on hours, not a measure of how much light reaches a leaf.

Two Groups, Two Different Sowing Dates

Almost every winter-greens article treats these crops as one list with one sowing month. They are not one list. They split by whether the plant has to be finished before the light goes.

Sow-By Dates — Group 1, City by City

Each date is that city's ten-hour date, minus the crop's days-to-maturity, minus two weeks for autumn slowdown. A date in the past is shown struck through, because on this page that is the answer: it tells you the crop has closed rather than leaving you to work it out.

Crop by Crop

Mâche (corn salad) — the one this window is really for

The most cold-hardy salad green a Canadian gardener can grow, and the crop that makes a September sowing worthwhile even now. It germinates in cooling soil, forms a low rosette, and then simply sits — unbothered by cold that flattens lettuce. On the south coast it holds through winter with no cover at all and gives a light picking from December; further in, it overwinters and finishes in February and March. Sow densely and thinly covered, 1 cm deep at most, because the seed is small and germination is slow in warm soil. Our own guide gives it 40–50 days to full-size rosettes, with smaller leaves usable earlier — but that number is the wrong lens here, because mâche is not being asked to finish before the light goes. Full corn salad guide →

Claytonia (miner's lettuce) — sow early-to-mid September

A mild, succulent green with round leaves clasped around the stem, and the other genuine overwinterer. Like mâche it is sown to establish rather than to finish, and it is at its best in the cold — the flavour is better in January than in October. It self-seeds readily once established, which on the coast means a bed sown this September will often re-appear on its own next autumn.

A gap we would rather state than fill. Claytonia, tatsoi, mizuna and komatsuna have no days-to-maturity figure in this site's crop table, so they get no calculated sow-by date above and we are not going to invent one. “Early-to-mid September” is the honest answer for claytonia on the coast, and it is what our overwintering guide already says. A missing number is better than a confident wrong one.

Arugula — the last of the size-up group

At 35 days it is the fastest thing on the list, which makes it the last door still open in the second week of September. It is also better in autumn than at any other time of year: the peppery heat that makes summer arugula unpleasant is a bolting response, and a September sowing never sees the heat or the long days that trigger it. Sow thickly, take it as a cut-and-come-again while growth lasts, and accept that from November it is a standing crop rather than a regrowing one.

Mustards and Asian greens

Mustard greens carry a 40-day figure and bok choy 45, so both close a few days ahead of arugula. Red mustards in particular colour up hard in cold and are among the better-looking things in a winter bed. Tatsoi and mizuna belong to the same group and behave the same way, but as noted above they carry no figure in our crop table, so treat early September as the practical limit rather than a computed one.

Spinach and winter lettuce

Overwintering spinach is worth sowing on its own terms even when it misses the size-up window, because it behaves like Group 2 — it survives as a small plant and resumes in February for a very early spring crop. Winter lettuce is the one to be honest about: at 45 days it closes earliest of everything here, in the first days of September on the coast and in late August in Prince George, so for this year it has gone. The overwintering varieties — Winter Density, Arctic King, Rouge d'Hiver — are genuinely different plants from summer lettuce and worth ordering for next season. We cover BC lettuce timing properly on its own page: When to Plant Lettuce in BC →

Shop Overwintering Lettuce Varieties →

Worth saying why this link and not a generic one: overwintering lettuce is not summer lettuce sown later. Winter Density, Arctic King and Rouge d'Hiver are bred for cold and short days, and a summer variety sown now will not behave like them whatever the sowing date says. West Coast Seeds is on Vancouver Island, so their variety notes are written for this climate rather than adapted from a US catalogue. Their full vegetable seed range →

Cover or No Cover — On the Coast It Is About Rain, Not Heat

This is the point where advice written for Ontario or for the American Midwest actively misleads a coastal BC gardener. In most of Canada a winter cover exists to hold heat against a hard freeze. In zone 8 on the south coast, the sustained hard freeze mostly does not arrive — and the thing that destroys a bed of winter greens is weeks of cold rain sitting on the leaves, followed by grey mould.

So the cover has to be a roof: a cold frame lid, a cloche, or clear poly stretched over hoops so that water runs off rather than through. A lightweight spun frost fabric is the wrong tool for this job, because it wets through and then lies on the foliage — which is worse than leaving the bed open. That is a real distinction, not a small one, and it is why we do not point you at a frost blanket here.

Vent it. A closed frame on a bright winter day heats quickly, and warm, still, humid air over wet leaves is precisely what botrytis wants. Open it any time the sun is out and the air is mild, close it before evening, and take damaged leaves off the plant rather than leaving them to rot in place. Spacing plants further apart than you would in summer does more for airflow than anything else you can do after the fact. Cold frame guide — build, glazing and daily venting →

Slugs Do Not Stop for Winter Here

A gardener arriving on the coast from a colder province is usually unprepared for this one. Slugs do not reliably go dormant in a mild wet zone 8 winter — conditions are close to ideal for them — and a bed of September seedlings can disappear in a week. The timing that works is bait at sowing, before there is visible damage to react to, because by the time you can see the damage the seedlings are already gone.

Harvesting in the Standstill

From roughly November to February there is no regrowth, so every harvesting habit built in summer has to change. Four rules cover it.

1. Outer leaves only, never the whole plant. There is nothing to replace what you cut. A plant harvested to the base in December is gone, not resting.
2. Take less than you think. About a third of a plant at a time is a reasonable ceiling in the dark months; the rest is the plant's reserve for February.
3. Never pick frozen leaves. A frozen leaf is brittle and bruises wherever it is handled, and the damaged tissue rots instead of recovering. Wait for the midday thaw, which on the coast usually comes.
4. Pick at midday, not dusk. Foliage disturbed in the evening stays wet all night, which is the botrytis pathway again.

Then in February the whole thing changes character. Light climbs back above ten hours on Feb 13 in Vancouver and Victoria, and the plants that spent winter holding still start growing again — weeks before anything spring-sown has germinated. On the coast that February resumption, rather than the winter picking, is often the real payoff.

Interior and Northern BC — Cold Frame, or Skip It

The light constraint barely changes across the province — Kamloops crosses ten hours on October 29, two days before Vancouver. The temperature constraint changes completely, and it is the one that decides this.

Kelowna and Kamloops sit in zone 6b. An uncovered winter salad bed there is not a standing crop, it is a loss. The realistic version is a cold frame or a well-built low tunnel, with mâche and claytonia as the crops most likely to come through and spinach a reasonable third. Prince George, at zone 4a, is a different proposition again: treat unheated winter salad as an experiment rather than a plan, and put the same effort into a February or March sowing under cover, where the return is far more reliable. BC hardiness zones, city by city →

Winter Salad Greens in BC — Common Questions