When to Plant Onions in New Brunswick
Published: April 24, 2026 · Updated: April 27, 2026
Onion timing is determined by day-length as much as frost dates. Use short-day varieties south of 35°N latitude (TX, FL, CA) and long-day varieties north of 35°N (OH, MN, NY).
Onions grow well in this province with appropriate variety selection and standard Canadian planting timing.
Onions Planting Window for New Brunswick
Start seeds indoors: March 1–8 (varies by city — earliest in southern Ontario, latest on the Prairies)
Transplant outdoors: April 12–22 (after last frost in your city)
Direct sow outdoors: April 12–22
Minimum soil temperature: 2°C (35°F)
Days to harvest: 90–120 days
Sun requirement: Full sun
⚠ CRITICAL: Choose variety based on your latitude. Short-day varieties for south of 35°N (Texas, Florida, California). Long-day varieties for north of 35°N (Ohio, Minnesota, New York). Intermediate varieties work in the middle band.
New Brunswick Cities — Onions Planting Dates
City-specific frost dates and onion planting windows for New Brunswick.
Growing Onions in New Brunswick
- Match variety to latitude: short-day south of 35°N, long-day north of 35°N, intermediate in between.
- Growing from sets (small bulbs) is fastest; growing from transplants gives the most variety options.
- Reduce watering as tops begin to fall over — dry conditions encourage tight, firm bulbs that store longer.
- Cure harvested onions 2–4 weeks in a warm, dry, airy location before storing — uncured onions rot quickly.
Companion Planting for Onions
In New Brunswick gardens, pair onion with Carrot, Tomato, Lettuce, Beet. Avoid planting near Bean, Pea, Asparagus, which compete with or inhibit onion growth.
Common Pests and Problems
Onions in New Brunswick are commonly affected by Onion Thrips, Onion Maggot, Downy Mildew, Neck Rot. Floating row covers installed at planting block most adult pests from laying eggs, and a weekly scouting routine catches infestations before they damage the crop.
Frequently Asked Questions
When should I plant onion in New Brunswick?
In New Brunswick (Canadian Zone 5b), start seeds indoors around March 1 and transplant around April 12. Onions grow well in this province with appropriate variety selection and standard Canadian planting timing.
What is the best onion variety for New Brunswick?
New Brunswick gardeners should prioritise varieties bred for shorter seasons or Canadian climates. For onions in Canadian Zone 5b, look for cultivars labelled under 120 days to maturity. Local nurseries and provincial seed exchanges curate varieties that ripen within Canadian frost-free windows.
How does New Brunswick's climate affect onion?
New Brunswick spans Canadian Zone 5b with frost-free seasons ranging from roughly 151 to 155 days. Onions actually prefer the cooler spring and fall windows typical of New Brunswick, making them one of the most reliable crops in the province.
Can I grow onion in containers in New Brunswick?
Yes. Container growing on balconies and patios extends the viable growing area across every Canadian province. Dark-coloured containers warm up faster in spring and extend the season on both ends. Choose a 5-gallon or larger pot for onion and water daily during hot summer weather, since containers dry out quickly.
When is the first fall frost in New Brunswick?
First fall frost dates in New Brunswick range from October 8 in the coldest areas to October 12 in the warmest. Most onion plantings in New Brunswick are spring-timed to harvest before the first fall frost rather than as a second fall crop.