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.

A common way of determining when to plant astilbe is to consult the USDA zone info for Washington.

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 means that you can plant them slightly earlier than plants that are more sensitive to the cold.

The earliest that you can plant astilbe in Washington 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. Any later than that and your astilbe may not have a chance to grow to maturity. If you are starting your astilbe indoors then you might be able to get away with starting them a little bit earlier.

Last Frost Date

In Washington the average date of last frost happens on April 15. It might get as low as -10°F during the coldest months of winter.

Always keep in mind that USDA zone info for Washington is not always accurate and the actual date of last frost changes from year to year. Half of the time in Washington you get a frost after April 15 so make sure that you are ready to cover your astilbe if you have one of those late frosts.

USDA Zone Info for Washington

Here is the info for USDA Zone 6a.

Average Date of Last Frost (spring)	April 15
Average Date of First Frost (fall)	October 15
Lowest Expected Low	-10°F
Highest Expected Low	-5°F

This means that on a really cold year, the coldest it will get is -10°F. On most years you should be prepared to experience lows near -5°F.

Plants to Grow in Washington

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