When to Plant Garlic in Ottawa, ON
Published: April 24, 2026 · Updated: April 27, 2026
Garlic is planted in fall and harvested the following summer — the opposite timing from most vegetables. It is one of the most hands-off, rewarding crops once established.
Ottawa's Canadian Zone 5b (USDA 5a) continental climate brings cold winters, hot summers, and higher frost risk than Toronto thanks to the inland location. The 153 frost-free days from early May through early October is adequate for most vegetables, but variety selection — short-season cultivars under 70 days — matters significantly.
Garlic Planting Calendar for Ottawa
Direct sow outdoors: October–November (plant cloves)
Harvest window: June (following year) – July (following year)
Minimum soil temperature: 10°C (50°F)
Days to harvest: 240–270 days
Sun requirement: Full sun
⚠ PLANTING SEASON IS OPPOSITE: Plant garlic cloves in fall (October–November) for harvest the following summer (June–July). This is unlike any other common vegetable.
Ottawa Climate Notes
Ottawa Valley winters are harsh. Choose short-season tomato varieties under 70 days (Stupice, Sunrise, Sub-Arctic Plenty) and transplant only after the May long weekend. Fall garden extends the productive season into October with cold-tolerant greens and brassicas.
Growing Tips for Garlic
- Plant individual cloves in October–November, pointed end up, 2 inches deep, 6 inches apart.
- Mulch with 3–4 inches of straw after the first hard freeze to insulate through winter.
- Remove garlic scapes (the curling flower stalks) in June from hardneck varieties to redirect energy to the bulb.
- Harvest when the bottom 3–4 leaves turn brown — typically June in most regions.
Companion Planting in Ottawa
Pair garlic with Tomato, Rose, Carrot, Cucumber for mutual benefit. Avoid planting near Bean, Pea, Parsley, which compete with or inhibit garlic growth.
Pests and Problems to Watch in Ottawa
The most common pest and disease pressure on garlic in Ottawa comes from Thrips, White Rot, Garlic Rust, Onion Fly. Floating row covers through the first 4–6 weeks after planting block adult pests from laying eggs, and a weekly scouting routine catches infestations before they damage the crop.
Other Ontario Cities
Frequently Asked Questions
When do I plant garlic in Ottawa?
Ottawa's last spring frost is around May 6. Direct sow October–November (plant cloves).
What Canadian hardiness zone is Ottawa?
Ottawa is in Canadian Zone 5b (USDA equivalent 5a). The continental inland climate delivers 153 frost-free days from May 6 to October 6, which shapes every planting date in the local calendar.
How long is Ottawa's growing season?
Ottawa has 153 frost-free days — from May 6 in spring to October 6 in fall. Garlic take 240–270 days to mature, which is tight in Ottawa's 153-day window. Choose the shortest-season varieties and protect from early fall frosts with row cover.
Can I grow garlic in containers in Ottawa?
Yes. Container growing on balconies and decks is practical in Ottawa — choose a 5-gallon or larger dark-coloured container to warm the root zone, use a high-quality potting mix, and water daily during hot summer weather. In milder climates, containers extend both spring and fall windows by several weeks.
What is the first fall frost in Ottawa?
Ottawa's average first fall frost is October 6. Most garlic in Ottawa is a single spring-timed planting designed to harvest before the first fall frost.