When to Plant Radishes in Hamilton, ON
Published: April 24, 2026 · Updated: April 27, 2026
The fastest crop in the garden — ready in 22–30 days. Direct sow 4–6 weeks before last frost and succession plant every 2 weeks for a continuous spring harvest.
Hamilton's Canadian Zone 6b (USDA 6a) climate benefits from the Niagara Escarpment's moderating effect. The 189 frost-free days make this one of the warmest regions in Ontario, with some sheltered sites reaching near-Zone 7 microclimate conditions. Melons, peppers, and eggplant succeed reliably where they would struggle elsewhere.
Radishes Planting Calendar for Hamilton
Direct sow outdoors: March 18–28
Harvest window: April 9 – April 17
Minimum soil temperature: 4°C (40°F)
Days to harvest: 22–30 days
Sun requirement: Full sun to partial shade
Fall crop planting: September 23–October 3 (harvest October 15)
⚠ Direct sow radishes 4–6 weeks before last frost — one of the fastest crops in the garden. Ready in as little as 22 days. Succession plant every 2 weeks for continuous harvest.
Hamilton Climate Notes
Hamilton/Niagara is the warmest part of Ontario. Near-Zone 7 microclimate conditions exist in sheltered sites near the escarpment. This region is Ontario's most productive for heat-loving crops including melons, eggplant, and peppers.
Growing Tips for Radishes
- Thin to 2-inch spacing when seedlings are an inch tall — crowded radishes produce small woody roots.
- Succession plant every 10–14 days from early spring through late spring for continuous harvest.
- Plant as a row marker for slow-germinating crops like carrots — radishes sprout in days and mark the rows.
- Harvest promptly at target size; over-mature radishes turn pithy, woody, and unpleasantly hot.
Companion Planting in Hamilton
Pair radish with Lettuce, Carrot, Pea, Cucumber for mutual benefit. Avoid planting near Hyssop, Grape, which compete with or inhibit radish growth.
Pests and Problems to Watch in Hamilton
The most common pest and disease pressure on radishes in Hamilton comes from Flea Beetle, Cabbage Root Maggot, Aphid. 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.
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Frequently Asked Questions
When do I plant radish in Hamilton?
Hamilton's last spring frost is around April 22. Direct sow March 18–28.
What Canadian hardiness zone is Hamilton?
Hamilton is in Canadian Zone 6b (USDA equivalent 6a). The Niagara Escarpment temperate climate delivers 189 frost-free days from April 22 to October 28, which shapes every planting date in the local calendar.
How long is Hamilton's growing season?
Hamilton has 189 frost-free days — from April 22 in spring to October 28 in fall. That is more than enough time to finish a full radish crop (22–30 days to maturity) before the first fall frost.
Can I grow radish in containers in Hamilton?
Yes. Container growing on balconies and decks is practical in Hamilton — 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 Hamilton?
Hamilton's average first fall frost is October 28. For a fall radish crop, plant around September 23–October 3 so plants mature before the first killing frost.