Before planting it is a good idea to find your USDA Zone info to estimate your garden schedule. The zone info helps tell us things like average date of last frost and lowest expected temperature for your area.

The first chance to plant polygonums in Washington should be determined by reviewing the USDA zone info.

Planting Calendar for Polygonums

Frost tolerance for polygonums:	Not tolerant of frost.
When to plant:	After the last frost when the weather gets warmer.

It's not a good idea to plant polygonums until after all chance of frost has passed because they do not do well in cold weather.

The earliest that you can plant polygonums in Washington is April. However, you really should wait until May if you don't want to take any chances.

The last month that you can plant polygonums and expect a good harvest is probably August. You probably don't want to wait any later than that or else your polygonums may not have a chance to really do well. If you are starting your polygonums indoors then you might be able to get away with starting them a couple of weeks earlier.

Last Frost Date

In Washington the average date of last frost happens on April 15. It might get as low as 0°F during the coldest months of winter.

Remember that USDA zone info for Washington may not be accurate from year to year 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 be sure to be ready to protect your polygonums in the event of one of those late frosts.

USDA Zone Info for Washington

Here is the info for USDA Zone 7a.

Average Date of Last Frost (spring)	April 15
Average Date of First Frost (fall)	October 15
Lowest Expected Low	0°F
Highest Expected Low	5°F

This means that on a really cold year, the coldest it will get is 0°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.