Saint John NB Planting Guide — Zone 6a Calendar & Frost Dates
Saint John NB planting guide — Zone 6a (warmest in NB), last frost May 8, first frost October 8, ~153-day season (longest in NB). Full calendar with indoor start and outdoor transplant dates for 20+ vegetables.
Saint John NB's last frost date is May 8 — the earliest in New Brunswick thanks to powerful Bay of Fundy moderation. First fall frost arrives around October 8, giving Saint John approximately 153 frost-free days in Zone 6a — the longest growing season in the province. The Kennebecasis valley communities (Quispamsis, Rothesay, Hampton) sit slightly inland and run 4–14 days later.
For a deeper dive on Saint John NB's frost dates — urban peninsula community-by-community breakdown (Uptown, South End, North End waterfront, West Saint John, East Saint John), Kennebecasis valley microclimate, Bay of Fundy moderation effects, and how Saint John compares to Halifax and Fredericton — see the dedicated Last Frost Date Saint John NB page. Use this guide alongside the seed starting calculator to build your full planting schedule.
Saint John NB at a glance: Last frost May 8 · First frost Oct 8 · Growing season ~153 days (longest in NB) · Hardiness zone 6a (warmest in NB). Cool-season crops start early April; brassicas + onions transplant late April; warm-season crops (tomatoes, peppers, beans, cucumbers) after May 18.
📅 Saint John NB's Key Frost Dates
Saint John NB Planting Calendar — Full Table
All dates calculated from Saint John NB's average last frost of May 8. Start indoors dates count backward from transplant date. Direct sow dates are when it's safe to plant outdoors.
| Vegetable | Start Indoors | Transplant Out | Direct Sow | Days to Harvest |
|---|---|---|---|---|
| 🍅 Tomatoes | Mar 27–Apr 10 | May 18–25 | — | 55–85 days |
| 🌶 Peppers | Mar 13–27 | May 22–Jun 1 | — | 60–85 days |
| 🥬 Cucumbers | Apr 24–May 1 | May 15–22 | May 15–22 | 50–65 days |
| 🎃 Zucchini / Squash | Apr 24–May 1 | May 15–22 | May 15–22 | 50–60 days |
| 🥦 Broccoli | Apr 3–17 | Apr 29–May 8 | — | 60–80 days |
| 🥭 Cabbage | Mar 27–Apr 10 | Apr 29–May 8 | — | 70–120 days |
| 🧀 Onions (seed) | Feb 27–Mar 13 | Apr 29–May 8 | — | 100–120 days |
| 🧀 Onions (sets) | — | — | Apr 29–May 8 | 65–75 days |
| 🥕 Carrots | — | — | Apr 24–Jun 1 | 70–80 days |
| 🫘 Bush Beans | — | — | May 15–Jun 5 | 50–60 days |
| 🌿 Peas | — | — | Apr 10–25 | 55–70 days |
| 🥕 Lettuce | Apr 10–24 | Apr 29–May 8 | Apr 24–Jun 15 | 45–60 days |
| 🍃 Spinach | — | — | Apr 15–May 15 | 40–50 days |
| 🥦 Kale | — | — | Apr 15–May 8 (+ Aug fall) | 55–75 days |
| 🪒 Radishes | — | — | Apr 10–Jun 10 | 25–35 days |
| 🥔 Potatoes (seed) | — | — | Apr 15–May 5 | 70–110 days |
| 🥦 Garlic (hardneck) | — | — | Oct 1–15 (previous year) | Harvest Jul |
Saint John NB Month-by-Month Planting Tasks
🌚 February–March
- Start onion seeds indoors (late Feb–early March)
- Start pepper seeds indoors (mid-March)
- Order seed potatoes and tender bedding plants
🌿 April
- Start tomato seeds indoors (early-to-mid month)
- Start broccoli, cabbage, lettuce indoors (mid-month)
- Direct sow peas, radishes, spinach outdoors (mid-month)
- Prepare beds — compost amendment
- Plant seed potatoes (mid-to-late month)
🌺 May
- Transplant brassicas, onions, lettuce (week 1)
- Direct sow carrots, kale, beets (early month)
- Transplant cucumbers, zucchini (after May 15)
- Transplant tomatoes (after May 18)
- Transplant peppers (after May 22)
- Direct sow bush beans (after May 15)
🍅 June–August
- Side-dress with compost (June)
- Mulch heavily for moisture retention
- Harvest peas, lettuce, radishes (June-July)
- Start fall brassicas indoors (July)
- Direct sow fall kale, spinach, lettuce (August)
- Watch for late blight on tomatoes (Bay of Fundy humidity)
🍁 September
- Main harvest: tomatoes, peppers, beans, squash
- Continue fall greens harvest
- Begin curing onions and garlic
🍂 October
- Final harvests — cover frost-sensitive crops
- Plant hardneck garlic (Oct 1–15)
- Mulch garlic beds heavily for overwintering
- Continue harvesting overwintering kale
Best Vegetables for Saint John NB's Climate
Saint John NB's Zone 6a maritime climate gives gardeners more flexibility than the rest of NB. Cool-season strengths: kale (excellent — overwinters with light protection), peas (spring + fall), broccoli (two crops possible), lettuce, spinach, root vegetables. The cool foggy Maritime summers favour these crops over heat-stressed inland varieties.
Warm-season opportunities (longer than rest of NB): full-size beefsteak tomatoes (80–90 days), heirloom peppers, cucumbers, zucchini, even short-season melons in the warmest spots. Bay of Fundy humidity creates significant late blight pressure on tomatoes from August onward — variety selection matters. Choose Defiant PhR, Mountain Magic, Legend, or Iron Lady for reliable blight resistance.
Hardneck garlic planted in mid-October overwinters reliably under snow cover and produces excellent heads — the Bay of Fundy region is reputed for high-quality garlic production. Overwintering kale works in Saint John in a way it doesn't elsewhere in NB — Winterbor planted in August can be harvested fresh through November and again in early spring with row cover protection.
Bay of Fundy Late Frost & Late Blight Protection
Late frost protection: a late frost after May 8 happens roughly 1 year in 5 in Saint John's urban peninsula. Bay of Fundy late frosts are usually -1 to -2°C and arrive with sea fog or cold Atlantic rain. Keep floating row cover (Reemay, Agribon) on hand until May 20. Cloches over individual seedlings on forecast frost nights. Kennebecasis valley gardeners should keep covers ready until May 25–June 1.
Late blight protection (the bigger Saint John challenge): Bay of Fundy humidity creates serious late blight pressure on tomatoes and potatoes from August onward. Mitigation: (1) choose blight-resistant varieties — Defiant PhR, Mountain Magic, Legend, Iron Lady; (2) stake tomatoes for airflow, prune lower leaves; (3) avoid overhead watering; (4) mulch heavily to prevent soil splash on lower leaves; (5) consider a simple plastic rain cover from August onward in the warmest tomato spot.
📍 Atlantic Canada Garden Resources
Plan Your Saint John NB Garden Season
Use the frost calculator for your exact postal code — Kennebecasis valley (Quispamsis, Rothesay, Hampton) runs 4–14 days later than the May 8 Saint John urban average.