The USDA Zone info is a great tool for gardeners to help us determine your gardening schedule. The zone info helps tell us things like average date of last frost and lowest expected temperature for your area.

The earliest that you can plant astilbe in Portland can be estimated by checking out the USDA zone info.

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 tend to make it in a tiny bit of cold which means that you can plant them just a tiny bit earlier in the year than plants that are more sensitive to the cold.

The earliest that you can plant astilbe in Portland 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 few weeks earlier.

Last Frost Date

In Portland the average date of last frost happens on April 15. You can expect an average low temperature of -15°F in the coldest months of winter.

It's important to remember that USDA zone info for Portland is an average and the actual date of last frost will vary from year to year. Since half of the time in Portland there is a last frost after April 15 be ready to cover your astilbe if you have a surprise late frost.

USDA Zone Info for Portland

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 Portland

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