Yes, you still have to sow seeds! May is one of the busiest planting months in Ontario, especially for warm-season veggies and easy direct-sow flowers.
May weather can still be unpredictable in Zones 4–6, so keep a frost blanket nearby if you’re planting early, and don’t rush heat-loving crops into cold soil.
Below you’ll find May planting separated into what to start indoors vs what to sow directly outside, organized week-by-week by zone.
Quick “How-To”
(so your seeds actually germinate)
Indoors (for starts)
- Use seed-starting mix (not heavy potting soil)
- Give 14–16 hours/day under a grow light
- Keep soil damp like a wrung-out sponge
- Harden off seedlings for 7–10 days before planting outside
Direct sow outdoors
- Loosen soil + rake smooth
- Plant at the depth on the packet (most are 2–3× seed width)
- Water gently and keep consistently moist until sprouted
- Mark your rows (so you don’t accidentally weed seedlings!)
Zone 4 | May (Petawawa / Pembroke)
Start Indoors (Zone 4)
| Week 1 |
Week 2 |
Week 3 |
Week 4 |
| Cucumber |
Squash |
Melon |
Pumpkins |
Direct Sow Outdoors (Zone 4)
| Week 1 |
Week 2 |
Week 3 |
Week 4 |
| Beans, Swiss chard, Sunflowers |
Beans, Dill, Nasturtiums |
Peas, Lettuce, Cosmos |
Peas, Radish, Calendula |
Plant (Seedlings/Roots) (Zone 4)
| Week 1 |
Week 2 |
Week 3 |
Week 4 |
| Haskap (plant) |
Currants/Gooseberries (plant) |
— |
— |
Zone 5 | May (Ottawa)
Start Indoors (Zone 5)
| Week 1 |
Week 2 |
Week 3 |
Week 4 |
| Cucumber |
Squash |
Melon |
Pumpkins |
Direct Sow Outdoors (Zone 5)
| Week 1 |
Week 2 |
Week 3 |
Week 4 |
| Beans, Swiss chard, Nasturtiums |
Beans, Dill, Cosmos |
Peas, Lettuce, Calendula |
Peas, Radish, Sunflowers (succession sow) |
Zone 6 | May (Brockville)
Start Indoors (Zone 6)
| Week 1 |
Week 2 |
Week 3 |
Week 4 |
| Cucumber |
Squash |
Melon |
Pumpkins |
Direct Sow Outdoors (Zone 6)
| Week 1 |
Week 2 |
Week 3 |
Week 4 |
| Beans, Swiss chard, Nasturtiums |
Beans, Dill, Cosmos |
Peas, Lettuce, Calendula |
Peas, Radish, Sunflowers (succession sow) |
Tools + supplies that make May sowing easier
- Seed-starting mix + trays (for indoor starts)
- Row cover/frost blanket (May insurance)
- Plant labels/markers
- Compost or soil booster (topdress before sowing)
- Watering wand or gentle nozzle (prevents seed washout)
Companion planting (easy wins)
-
Cucumber + dill (classic pairing)
-
Beans + nasturtiums (pollinators + “trap crop” vibes)
-
Lettuce + calendula (flowers bring beneficial insects; lettuce appreciates a little shade later)
-
Radish + peas (radish is quick; peas are slower)
Need help deciding what’s safe to plant this week?
Pop in and tell us your zone and what you’re growing, we’ll help you time it properly, pick varieties, and grab the supplies that make May planting smoother.
