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.

By referring to the USDA zone info for Union it's a good idea to estimate when it's the best time 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 are barely cold tolerant which means that you can get them planted just a bit earlier than other frost tender plants.

The earliest that you can plant astilbe in Union 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. If you wait any later than that and your astilbe may not have a chance to really do well. Starting your astilbe indoors is a great way to get them started a little bit earlier.

Last Frost Date

The average date of last frost is April 15 in Union. You can expect an average low temperature of -10°F in the coldest months of winter.

Since the USDA zone info for Union may not be accurate from year to year the actual date of last frost is different every year. Half of the time in Union you get surprised by a frost after April 15 so make sure that you are ready to cover your astilbe in the event of one of those late frosts.

USDA Zone Info for Union

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 Union

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