Fall Brassicas Canada
The family that defines fall gardening — broccoli, kale, cabbage, Brussels sprouts, cauliflower, kohlrabi, bok choy. Cool weather sweetens them, frost concentrates their sugars, and pest pressure drops sharply from summer.
Fall brassicas Canada: sow or transplant late July through mid-August, harvest September through November (longer in zones 6+ with row cover). The seven fall brassicas: broccoli, kale, cabbage, Brussels sprouts, cauliflower, kohlrabi, bok choy. Frost sweetens them — kale and Brussels sprouts taste transformed after the first light frost, and most fall brassicas tolerate down to −3 to −5°C with no protection. Cabbage worm and flea beetle pressure drops to near-zero by mid-September. The easiest fall brassicas for beginners: kale, bok choy, kohlrabi. The hardest: cauliflower (timing-sensitive) and Brussels sprouts (long 90–100 day season).
Why Fall Beats Spring for Brassicas
Three factors make Canadian fall brassicas dramatically better than spring-grown ones. Frost-sweetening — when night temperatures drop below 5°C, brassicas convert starches to sugars as a cell-protective measure. The result is sweeter cabbage, mellower Brussels sprouts, richer-flavoured kale, sweeter broccoli. This is the single most-overlooked secret of cold-climate vegetable gardening.
Pest collapse — cabbage worm, flea beetle, and aphid populations crash with the first cool nights of September. Spring brassicas constantly battle these pests with row cover, Bt sprays, and hand-picking; fall brassicas largely escape them. Most fall transplants set out in early August are essentially pest-free by the time they're heading up in October.
No bolting — spring-sown broccoli and bok choy frequently bolt (flower prematurely and become unmarketable) when summer heat arrives. Fall plantings mature into cooling weather and never trigger the bolt response. Net result: fall brassicas are easier, sweeter, less pest-damaged, and more flavour-complex than spring brassicas grown by the same gardener in the same garden.
The Seven Fall Brassicas
🥴 Kale (most forgiving)
Most cold-hardy brassica (−10°C unprotected). Sweetens dramatically after first frost. 60-day maturity. Best varieties: Winterbor, Red Russian, Lacinato (Dinosaur), Westlandse Winter. Overwinters in zones 5+ for early-spring harvest.
🥦 Broccoli
No more heat-bolting! Fall broccoli forms heads in cool October weather. 60–75 days from transplant. Best varieties: Belstar, Marathon, Calabrese. Side shoots produce for 3–5 weeks after main-head harvest.
🥔 Cabbage (storage star)
Stores 4–6 months in a root cellar at 0–2°C. 70–100 days from transplant. Best storage varieties: Storage No. 4, Brunswick, Danish Ballhead, Deadon. Tolerates −5°C in field; harvest before hard freeze.
🌵 Brussels Sprouts
Inedible from summer; magnificent after fall frosts. 90–100 days from transplant — sow earliest of any fall brassica. Best varieties: Diablo, Long Island Improved, Falstaff (purple). Leave on stalk and pick all winter in zones 6+.
🥐 Cauliflower (trickiest)
Needs steady cool weather without sharp swings. 65–80 days from transplant. Best varieties: Snow Crown, Cheddar (orange), Graffiti (purple). Tie outer leaves over the curd to blanch white. Harvest before hard frost.
🥕 Kohlrabi (fastest swollen stem)
50–55 days from sow. Sweet, crisp swollen-stem brassica. Best varieties: Kossak (giant, 8–10 inches, stays tender), Korridor, Purple Vienna. Eat raw or cooked; tolerates light frost.
🥤 Bok Choy (fastest of all)
40–45 days from seed — the fastest brassica. Cool fall weather prevents the bolting that ruins spring-sown bok choy. Best varieties: Joi Choi, Toy Choi, Win-Win Choi. Harvest entire plants when 15–20 cm tall.
❄️ Overwintering Bonus
Sprouting broccoli (Purple Sprouting, Late Purple) sown August survives winter as a small plant and produces flush of mini-broccoli March–April — weeks before any spring-sown crop. Zones 6+ for reliable overwintering.
Sow-by-Date by City (Brassica + City)
The critical math: count backwards from your first fall frost date by the brassica's days to maturity PLUS a 14-day buffer for autumn's slower growth. The table below shows last-transplant-by dates for the four most-grown fall brassicas across major Canadian cities. Direct-sown crops (kohlrabi, bok choy) can go in slightly later because they skip the indoor-start lead time.
| City | First frost | Brussels sprouts (95 d) | Cabbage (80 d) | Broccoli (60 d) | Kale (60 d) |
|---|---|---|---|---|---|
| Vancouver / Victoria | Nov 25 | Aug 8 | Sept 2 | Sept 22 | Sept 22 |
| Toronto / Hamilton | Oct 30 | July 13 | Aug 7 | Aug 27 | Aug 27 |
| Mississauga / Brampton | Oct 25 | July 8 | Aug 2 | Aug 22 | Aug 22 |
| Ottawa | Oct 15 | June 28 | July 23 | Aug 12 | Aug 12 |
| Montreal | Oct 10 | June 23 | July 18 | Aug 7 | Aug 7 |
| Halifax / Charlottetown | Oct 15 | June 28 | July 23 | Aug 12 | Aug 12 |
| St. John's NL | Oct 13 | June 26 | July 21 | Aug 10 | Aug 10 |
| Winnipeg / Saskatoon | Sept 25 | June 8 | July 3 | July 23 | July 23 |
| Calgary / Regina | Sept 18 | June 1 | June 26 | July 16 | July 16 |
| Edmonton | Sept 22 | June 5 | June 30 | July 20 | July 20 |
| Sudbury | Sept 17 | May 31 | June 25 | July 15 | July 15 |
All dates are transplant by deadlines (not seed-start dates — add 6 weeks for indoor lead time). Calculated as: first frost − (days to maturity + 14-day fall slowdown buffer). Row cover or a cold frame buys an additional 2–4 weeks at the back end. See /frost-calculator for your exact first-frost date.
Frost Timing — When Frost Helps vs Hurts
The most important fall-brassica skill is knowing which frost is good (it sweetens) and which frost is bad (it damages curds and tender tissue). Below is the working hierarchy.
Welcomes all fall brassicas. Sweetens kale, Brussels sprouts, cabbage, broccoli. Doesn't damage cauliflower curds. Leave plants exposed — no protection needed.
Most fall brassicas still fine uncovered. Harvest cauliflower heads now — the curds bruise. Broccoli heads can take it but cover if convenient. Row cover gains 2–3°C if forecast.
Harvest cabbage heads (storage), Brussels sprouts (or leave on stalk with row cover). Kale + collards survive uncovered down to −10°C. Cauliflower + broccoli should already be harvested by now.
Even kale needs cold frame or polytunnel below −10°C. Brussels sprouts on the stalk hold under row cover. Most fall brassicas have either been harvested or are overwintering at this point.
Pest Pressure: Fall vs Spring (Why Fall Wins)
Cabbage worm (imported cabbageworm): peak pressure June–August, drops 80% by mid-September, near-zero by mid-October. Flea beetle: peak May–July, drops 90% by September. Aphids: peak July, drops sharply by mid-September. Cabbage looper: similar timing to cabbage worm, near-zero by October. Cabbage maggot: a spring pest only — the fall fly generation rarely lays in cool soil.
Practical takeaway: row cover at transplant time in early August is the main pest defence. By mid-September you can largely remove the row cover and let plants finish in the open. The clean, low-pest fall harvest is one of the biggest reasons brassicas grown in autumn are easier than in spring.
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After the Harvest — Preserving Brassicas
Fall brassicas preserve beautifully — arguably more reliably than any other vegetable family. Cabbage stores fresh in a root cellar (0–2°C, 90% humidity) for 4–6 months; an unheated garage often works. Kale freezes well after blanching, dehydrates into chips, and ferments into sauerkraut-style kraut. Brussels sprouts hold on the stalk in the garden through several frosts — pick as needed. Lacto-fermented sauerkraut from fall cabbage is the textbook Canadian preserve: shred cabbage, salt at 2% by weight, pack and ferment at room temperature for 2–4 weeks. Broccoli florets freeze well after blanching for 2–3 minutes. Cauliflower pickles brilliantly. Our sister site covers the full Canadian preserving playbook with safe times and temperatures: HarvestGuide.ca — Canadian canning, freezing & dehydrating guides →
Common Questions About Fall Brassicas
Should I start fall brassicas from seed or buy transplants?
For most home gardeners: start your own from seed indoors in late June or early July. Canadian garden centres rarely stock fall brassica transplants in late July or August — their selection is finished for the season by mid-July. Sowing your own gives you access to fall-specific varieties (Diablo Brussels sprouts, Storage No. 4 cabbage, Belstar broccoli) that nurseries don't carry. Start seeds in 10 cm pots under lights or in a partly-shaded outdoor location; transplants are ready in 4–6 weeks. The exception: bok choy and kohlrabi are usually direct-sown outdoors and skip the indoor-start step entirely.
Can I plant fall brassicas where spring brassicas just finished?
No — this is the one rule with no exceptions. Brassicas should not follow brassicas in the same bed in the same year. Two reasons: pest larvae (cabbage worm pupae, cabbage maggot pupae) overwinter in the soil where their food source was; and clubroot disease (Plasmodiophora brassicae) builds up in soil that grows brassicas back-to-back. Rotate brassicas to a bed that grew beans, peas, lettuce, tomatoes, or any non-brassica in the spring. Brassicas can return to the original bed safely after 3–4 years of other crops.
Why didn't my fall broccoli form a head?
Three common causes: started too late (the plant didn't have enough warm days to bulk up before cool weather slowed growth); insufficient nitrogen (broccoli needs steady N to push head formation; topdress with finished compost at transplant); transplant shock (broccoli is sensitive to root disturbance — transplant in cool evening hours with deep water, and don't bare-root the seedling). Bolt-resistant fall varieties (Belstar, Marathon, Calabrese) form heads more reliably than spring-bred varieties (which often don't head up properly in fall light conditions).
When are Brussels sprouts ready to harvest in Canada?
After at least one light frost. Brussels sprouts harvested before frost taste bitter and sulphurous — the flavour transformation only happens after cold-induced sugar conversion. Wait until your first light frost (typically late September in zone 5, mid-October in zone 6, late October in zone 7) and then start picking. Pick from the bottom of the stalk upward as the sprouts mature; lower sprouts ripen first. In zones 6+ leave the stalk in the garden through hard frost and pick all winter — the sprouts continue to mature and become even sweeter into December.
Plan Your Fall Brassica Schedule
Find your first fall frost date and count backwards. The full fall-planting playbook covers leafy greens, roots, and overwintering crops too — brassicas are the headline act but not the only show.