What to plant this week in Winnipeg, MB
With temperatures hovering near the -35°F minimum and an average first frost looming for September 20, Winnipeg gardeners must treat this week as a final sprint to harvest late crops like Winter Squash and Potatoes before the freeze sets in. While there are no new transplants available right now, it is the perfect time to sow Garlic cloves directly into the soil to establish roots for next year's summer bounty.
The next 7 days
Winnipeg, MBGrowing in Winnipeg right now
- Protect your Potato and Rutabaga beds with thick row covers or mulch immediately, as Winnipeg's rapid autumn chill can stunt tuber development if left exposed too long.
- Focus irrigation on early-morning watering only; late afternoon moisture increases fungal pressure in our heavy clay soils which retain water poorly during cold snaps.
- Do not delay harvesting Brassicas like Brussels Sprouts and Leeks; the first hard frost often sweetens them, but wind damage becomes a risk once temperatures dip below zero.
- Keep an eye on Shiso and Borage as they are among the last tender perennials to go before the ground freezes solid by late September.
Sow this week
1 crops- Garlic
Transplant this week
Nothing is due to go out this week.
Harvest soon
29 crops- Beefsteak Tomato
- Borage
- Brussels Sprouts
- Bush Bean
- Carrot
- Cleome (Spider Flower)
- Cosmos
- Dahlia
- French Marigold
- Garden Geranium (Zonal)
- Garden Verbena
- Garlic
- Lantana
- Leek
- Ornamental Sweet Potato Vine
- Parsnip
- Petunia
- Pole Bean
- Potato
- Rutabaga
- Scarlet Runner Bean
- Shiso (Japanese Basil)
- Summer Savory
- Sunflower
- Vinca (Madagascar Periwinkle)
- Winter Squash
- Yellow Summer Squash
- Zinnia
- Zucchini
Seasonal tips
- Clear away spent vegetable plants now to prevent disease carryover into winter.
- Divide perennials like borage, garden verbena, and zinnia while the soil is still warm.
- Gather all fallen leaves and debris from around your garlic patch to keep it clean.
Pest & disease watch
- Watch for aphid colonies swelling on the undersides of remaining Zinnias and Cosmos, which can weaken plants just as they need energy for final tuber or bulb storage.
- Monitor Potato fields closely for Colorado Potato Beetles, as their life cycle accelerates in our short summer window before the frost kills them off naturally.
- Check Brussels Sprouts and Sunflowers for fungal leaf spots common in Winnipeg's humid fall mornings when leaves stay wet after dew.
Watering this week
Reduce watering significantly now that harvest is underway, allowing the soil to dry out between the last few waterings before frost.
Mark your tomato and pepper locations with stakes so you can easily find them when spring planting begins next year.
Winnipeg gardening questions
3Can I still sow Garlic now or do I have to wait until next spring?
Yes, this is the ideal time to plant Garlic cloves as they need a cold period to form bulbs for harvest next summer. Push them into the ground at least 4 inches deep in loose soil to ensure good root penetration before winter.
My Winter Squash and Yellow Summer Squash look fine but I'm worried about frost damage.
Harvest these immediately if you see any browning or chilling on the leaves, as the first frost can rot the fruit from the inside out. Cut them with a few inches of stem attached to preserve their protective waxy coating during storage.
Are my Borage and Shiso perennials safe for another year in Winnipeg?
These plants cannot survive the winter outdoors, so you must dig up the roots carefully if you want to start them indoors next spring. Alternatively, allow them to go to seed now to self-sow into the cracks of your garden bed.
Other cities in zone 3b
4See the full zone 3b guide → · Plan your Winnipeg garden in SproutGuide →