Before planting it is a good idea to find your USDA Zone info to estimate your garden schedule. The most important data that the zone info tells us is average last frost and the lowest expected temperature for your area.

You should be able to determine when you can plant astilbe by referring to the USDA zone info for Coralville.

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 are barely cold tolerant which tells us that you can get them planted just a bit earlier than other plants that might not handle the cold.

The earliest that you can plant astilbe in Coralville is March. However, you really should wait until April 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. You probably don't want to wait any later than that or else your astilbe may not have a chance to fully mature. You can get started a little bit earlier by starting your astilbe indoors.

Last Frost Date

On average the last frost is on April 15 in Coralville. In the coldest months of winter you can expect an average low temperature of -15°F.

Since the USDA zone info for Coralville is just an average the actual date of last frost changes from year to year. Since half of the time in Coralville last frost occurs after April 15 be ready to protect your astilbe in the event of one of those late frosts.

USDA Zone Info for Coralville

Here is the info for USDA Zone 5b.

Average Date of Last Frost (spring)	April 15
Average Date of First Frost (fall)	October 15
Lowest Expected Low	-15°F
Highest Expected Low	-10°F

This means that on a really cold year, the coldest it will get is -15°F. On most years you should be prepared to experience lows near -10°F.

Plants to Grow in Coralville

You may be interested in your other planting guides for Coralville.