Before planting it is a good idea to find your USDA Zone info to figure out 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.

The USDA zone info for Denver can be looked at to figure out when it's possible to plant astilbe.

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 well in a tiny bit of cold which means that you can plant them slightly earlier in the year than more sensitive plants.

The earliest that you can plant astilbe in Denver 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. You can get started a few weeks earlier by starting your astilbe indoors.

Last Frost Date

The average date of last frost is April 15 in Denver. In the coldest months of winter you can expect an average low temperature of -15°F.

Remember that USDA zone info for Denver is an average and the actual date of last frost can change quite a bit from year to year. Half of the time in Denver there is a last frost after April 15 so make sure that you are ready to protect your astilbe if you have a late frost.

USDA Zone Info for Denver

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 Denver

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