Before planting it is a good idea to find your USDA Zone info to figure out your garden schedule. The zone info helps tell us things like average date of last frost and lowest expected temperature for your area.

It's a good idea to determine when to plant astilbe by using the USDA zone info for Great Falls.

Planting Calendar for Astilbe

Frost tolerance for astilbe:	Tolerant of a very small amount of frost.
When to plant:	Up to 3 weeks before last frost.

Astilbe do ok in a tiny bit of cold which means that you can plant them slightly earlier in the year than other plants that might not handle the cold.

The earliest that you can plant astilbe in Great Falls is April. However, you really should wait until May if you don't want to take any chances.

The last month that you can plant astilbe and expect a good harvest is probably August. If you wait any later than that and your astilbe may not have a chance to really do well. You can get started a few weeks earlier by starting your astilbe indoors.

Last Frost Date

On average the last frost when the weather gets warmer is on May 15 in Great Falls. In the coldest months of winter you should expect an average low temperature of -30°F.

Keep in mind that the actual date of last frost is not always accurate because it is based on the USDA zone info for Great Falls and it changes from year to year. Since half of the time in Great Falls it frosts late in the year after May 15 be ready to cover your astilbe if you have one of those late frosts.

USDA Zone Info for Great Falls

Here is the info for USDA Zone 4a.

Average Date of Last Frost (spring)	May 15
Average Date of First Frost (fall)	September 15
Lowest Expected Low	-30°F
Highest Expected Low	-25°F

This means that on a really cold year, the coldest it will get is -30°F. On most years you should be prepared to experience lows near -25°F.

Plants to Grow in Great Falls

You may be interested in your other planting guides for Great Falls.