What to plant this week in Winnipeg, MB
With average first frost arriving on Sep 20, Winnipeg gardeners have a narrow window to push late-season crops like Beefsteak tomatoes and pumpkins toward maturity before the ground freezes. This week marks a critical transition where you must prioritize hardy fall harvests while preparing for an immediate return to dormant storage crops like garlic in early October.
The next 7 days
Winnipeg, MBGrowing in Winnipeg right now
- Protect Brassicas like Brussels sprouts with row covers or frost cloth immediately, as nights can drop rapidly close to the -35°F extreme even after mid-September.
- Harden off cold-tolerant perennials such as Prairie Gentian and Garden Verbena now; do not wait for cooler temps as sudden freezes are common this time of year.
- Stop watering ornamental Sweet Potato Vines heavily; excess moisture before a hard freeze can cause root rot in Winnipeg's heavy clay soils.
- Begin sorting your fall harvest like parsnips and leeks to store in a cool, dry place or bring them inside given the short season.
Sow this week
1 crops- Garlic
Transplant this week
Nothing is due to go out this week.
Harvest soon
15 crops- Beefsteak Tomato
- Brussels Sprouts
- Bush Bean
- Cosmos
- Dahlia
- Garden Verbena
- Garlic
- Leek
- Lisianthus (Prairie Gentian)
- Ornamental Sweet Potato Vine
- Parsnip
- Potato
- Pumpkin
- Sunflower
- Winter Squash
Seasonal tips
- Finish succession sowings of Bush Beans now that the soil has warmed up significantly.
- Apply a thick layer of straw or leaves around Winter Squash and Pumpkin to protect them from early frosts.
- Prune dead foliage off Cosmos and Dahlia plants immediately after harvesting to keep the garden tidy.
Pest & disease watch
- Watch for late-season aphid colonies on sunflowers and dahlias which may spread quickly before the first frost shuts down plant growth.
- Monitor squash vine borers on winter squash plants as they can still lay eggs during warm daytime spikes in late September.
- Check garlic beds for fungal issues like white rot, though the primary focus now is ensuring cloves are healthy enough for storage or next year's planting.
Watering this week
Water deeply in the morning to help summer crops finish strong, but reduce frequency as autumn air cools down.
Since Garlic is listed for sowing now, ensure your cloves are firm and free of rot before pushing them into cool soil.
Winnipeg gardening questions
3Can I still plant new tomatoes now that we're close to the Sep 20 frost date?
It is too late for outdoor tomato transplants in Winnipeg; any remaining Beefsteak fruit must be harvested immediately as they will not ripen fully before a hard freeze.
When should I start planting garlic for next year's crop?
While the zone facts list garlic under 'sow now,' this refers to late autumn planting after the ground freezes in October, allowing cloves to establish roots before spring warmth returns.
How long can I keep harvesting parsnips and winter squash outdoors?
You can leave root crops like parsnips and potatoes in the ground until soil temperatures drop near freezing, but move pumpkins indoors once nights consistently stay below 40°F to prevent rot.
Other cities in zone 3b
4See the full zone 3b guide → · Plan your Winnipeg garden in SproutGuide →