Now
22°C · Partly cloudy
Today
23° / 15°
Soil 6 cm
18°C
First frost
~49 days (Oct 27)
Gardening in Ottawa
AI field guide · refreshed weeklyOttawa Gardening: Early Fall Planting & Harvest (Sept 8–14)
Zone 5a means your first fall frost arrives around October 27—you have 49 days of growing season left. Soil at 18°C is still warm enough for cool-season crops to germinate and establish quickly. Spring frost typically hits May 6, so plan next year's early sowings accordingly. This week's rain (12–16 mm mid-week) will help newly seeded beds; temperatures dropping to 7°C by Sept 11 signal the shift to autumn conditions.
Sow outdoors now
Spinach (e.g., 'Space' or 'Bloomsdale')
Direct-sow now for a 40–50 day harvest before hard frost; soil at 18°C is ideal. Space 10 cm (4 in) apart in rows 30 cm (12 in) apart.
Arugula (Eruca sativa)
Sow thickly for baby leaves in 3–4 weeks or mature plants in 6–8 weeks. Tolerates light frosts and tastes sweeter after a chill.
Radish (e.g., 'Cherry Belle', 'Watermelon')
Ready in 25–30 days; sow in succession every 2 weeks through mid-September. Fall radishes are crisp and mild.
Mâche (corn salad, Valerianella locusta)
Sow now for winter harvest; extremely cold-hardy and germinates well at 18°C. Thin to 15 cm (6 in) spacing.
Turnip (e.g., 'Purple Top', 'Hakurei')
Sow for roots and greens; matures in 50–70 days depending on variety. Thin to 10 cm (4 in) for roots, closer for greens.
Start indoors now
Kale (e.g., 'Lacinato', 'Winterbor')
Start seeds indoors now for transplants in 4–5 weeks; they'll establish before hard frost and improve in flavor after freezing. Harden off by late September.
Cabbage (e.g., 'January King', 'Savoy')
Sow indoors for transplants in 3–4 weeks; late-season cabbage stores well. Needs 60–90 days to maturity, so transplant by late September.
Broccoli (e.g., 'Waltham 29', 'Arcadia')
Start indoors now for transplants by late September; fall broccoli is less prone to bolting than spring crops. Needs 55–100 days to head.
Harvest now
Tomatoes (all types)
Pick all mature fruit before the first hard frost (Oct 27); ripen indoors on a sunny windowsill. Green tomatoes will color over 2–4 weeks at room temperature.
Peppers (sweet & hot)
Harvest mature peppers now; plants will slow as nights cool. Leave smaller fruit to ripen indoors if needed.
Beans (bush & pole)
Pick pods regularly to encourage final flushes before frost. Shell beans for drying should be left on the plant until pods brown.
Squash & Pumpkins
Harvest when skin resists fingernail puncture; cure in a warm, dry spot for 1–2 weeks before storage. Leave 5 cm (2 in) of stem attached.
Tasks this week
- Plant garlic cloves 5 cm (2 in) deep, 15 cm (6 in) apart, by late September for spring harvest; mulch heavily after soil freezes.
- Deadhead spent flowers on perennials and annuals to redirect energy into root establishment before frost.
- Divide spring-blooming perennials (hostas, daylilies, peonies) after foliage yellows; replant immediately or pot up for spring.
- Sow cover crops (winter rye, hairy vetch) on empty beds to prevent erosion and add nitrogen; they'll winter-kill or be tilled in spring.
- Cut back ornamental grasses to 10–15 cm (4–6 in) before they become woody; leave seed heads for wildlife if desired.
Watch out for
- Powdery mildew thrives in cool, humid fall weather—thin crowded plants and water at soil level only.
- Squash vine borers may still be active; check stems for sawdust-like frass and inject Bt or wrap stems with foil.
- Early frost risk after Sept 11 (lows to 7°C): have frost cloth ready for tender crops like tomatoes, peppers, and basil.
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