What to plant this week in Great Falls, MT
With average last frost dates landing around May 12, Great Falls gardeners are currently in a strict waiting period where no seeds can be sown and nothing can be transplanted. The brutal cold snaps typical of Zone 4b mean your dormant beds will see temperatures dip to -25°F before the soil fully thaws.
The next 7 days
Great Falls, MTGrowing in Great Falls right now
- Wait for stable ground thawing after late April snows; frozen soil prevents root establishment even if air temps rise briefly above freezing.
- Apply a thick layer of pine straw or shredded leaves now as a mulch, but keep it away from emerging buds to protect against late spring freeze damage.
- Check your greenhouse or cold frame vents frequently; rapid temperature swings between polar vortex lows and sunny May afternoons can stress early-budding perennials.
- Great Falls' heavy clay-loam retains moisture well once thawed, so avoid over-watering dormant shrubs as the ground is already saturated from winter precipitation.
Sow this week
No direct sowing windows open this week.
Transplant this week
Nothing is due to go out this week.
Harvest soon
No harvest windows opening just yet.
Seasonal tips
- Finish all spring soil preparation now so you can move quickly to sowing once temperatures rise above 40°F.
- Apply a layer of mulch over winter-weeded areas to suppress weeds as they begin to push through.
- Review your crop calendar and order seeds or start indoor seedlings for late May planting dates.
Pest & disease watch
- Late-winter voles are active under snowpack and emerging grass shoots; inspect mulch mounds for chew marks on crowns before green-up.
- Watch for early aphid colonies forming on protected evergreens or hardy ornamentals once soil temperatures consistently hit 45°F.
- Dormant spray applications may still be viable in late April to target overwintering insect eggs, but timing is critical with the fluctuating freeze-thaw cycle.
Watering this week
Hold off on regular watering until the ground thaws and daytime highs consistently reach 50°F to avoid waterlogging frozen roots.
Clean up any remaining debris from last winter's garden now to reduce habitats for overwintering pests before spring planting begins.
Great Falls gardening questions
3Can I start my vegetable seeds indoors now for a Great Falls summer?
Not yet; you must wait until after the last frost date of May 12 before moving seedlings outside. Starting too early risks killing tender plants when a sudden -25°F dip occurs in late spring.
My tomatoes are showing flower buds despite the cold forecast—what should I do?
If temperatures stay above freezing, let nature take its course since tomato flowers can set fruit even after brief cold snaps. Cover the plants with frost cloths overnight if a freeze is predicted within 48 hours.
Is it safe to remove winter mulch from my rose bushes now?
Hold off until late May when the danger of hard freezes has passed and the soil warms significantly. Removing insulation too early exposes sensitive roots to the freezing nights that still occur in Great Falls during April.
Other cities in zone 4b
3See the full zone 4b guide → · Plan your Great Falls garden in SproutGuide →