What to plant this week in Great Falls, MT
Great Falls gardeners are in the final stretch of summer, with frost-free growing season officially ending October 1st. This week marks the critical harvest window for heat-loving crops like watermelon and zucchini before autumn rains arrive. While garlic can still be sown now, focus your energy on pulling those maturing melons and beans while they are sweet.
The next 7 days
Great Falls, MTGrowing in Great Falls right now
- Protect late-season squash and corn with row covers immediately if temperatures dip toward -25°F; the cold-hardy nature of our zone 4b soil doesn't guarantee warmth for tender crops in October.
- Take advantage of the relatively dry Montana summers to finish harvesting watermelons and honeydew, but be ready to irrigate heavily after early autumn storms.
- Sow garlic now as soon as the ground is workable; Great Falls' short season requires this timing to ensure bulbs mature before the first frost in mid-October.
- Avoid transplanting anything new this week; all transplants should already be hardened off or harvested, leaving only cool-season sowings like garlic and parsnips.
Sow this week
1 crops- Garlic
Transplant this week
Nothing is due to go out this week.
Harvest soon
44 crops- Basil
- Borage
- Brussels Sprouts
- Bush Bean
- Cantaloupe
- Celery
- Cleome (Spider Flower)
- Cosmos
- Cowpea (Black-Eyed Pea)
- Cucumber
- Dahlia
- Edamame
- Fennel
- Flour Corn
- French Marigold
- Garden Verbena
- Garlic
- Ghost Pepper (Bhut Jolokia)
- Gourd (Ornamental/Bottle)
- Habanero Pepper
- Honeydew Melon
- Leek
- Lima Bean
- Lisianthus (Prairie Gentian)
- Loofah (Luffa)
- Nasturtium
- Ornamental Sweet Potato Vine
- Parsnip
- Pole Bean
- Potato
- Pumpkin
- Scarlet Runner Bean
- Shiso (Japanese Basil)
- Summer Savory
- Sunflower
- Sweet Corn
- Thai Basil
- Tomatillo
- Vinca (Madagascar Periwinkle)
- Watermelon
- Winter Squash
- Yellow Summer Squash
- Zinnia
- Zucchini
Seasonal tips
- Begin succession sowing bush beans and cucumbers every two weeks for continuous yields through summer.
- Apply a fresh layer of mulch around established plants to retain moisture as spring temperatures fluctuate.
- Prepare your soil beds now that the danger of frost has passed to ensure optimal root growth.
Pest & disease watch
- Watch for cucumber beetles on your remaining bush beans and cucumbers as they seek shelter before the freeze.
- Check tomato vines and tomatillos for late season spider mites, which can flourish during dry spells in autumn.
- Monitor squash plants for powdery mildew, a common issue when humidity spikes after our characteristic early fall rain.
Watering this week
Water deeply in the morning to encourage strong root development while minimizing evaporation and fungal risks.
Since garlic is being sown now, ensure you plant it a few weeks before your average last frost date of May 12 for a robust harvest next fall.
Great Falls gardening questions
3Can I still transplant peppers or basil now in Great Falls?
No, do not attempt to transplant sensitive crops like bell pepper or basil this week; the average last frost date is May 12, but by October 1st, any new transplants will be killed instantly.
What is the best time to sow garlic for next year's crop?
This week is ideal for sowing garlic in Great Falls; get it into the ground now so roots can establish before the deep freezes of winter set in.
How do I know when my watermelon and cantaloupe are ready to harvest?
Harvest these melons soon if the rind becomes dull rather than shiny, or if they slip easily off the vine; wait no longer as the first frost on October 1st will ruin their flavor.
Other cities in zone 4b
3See the full zone 4b guide → · Plan your Great Falls garden in SproutGuide →