When to Plant Polygonums in Washington, IL

One of the first steps you take when you are determining your gardening schedule is find your USDA Zone info. The zone info helps tell us things like average date of last frost and lowest expected temperature for your area.

In Washington you can determine when it's possible to plant polygonums by reviewing the USDA zone info.


Planting Calendar for Polygonums

Frost tolerance for polygonums: Not tolerant of frost.
When to plant: After all chance of frost has passed.

It's probably not a good idea to plant polygonums until after the last frost because they are not cold tolerant.

JanFebMarAprMayJunJulAugSepOctNovDec
Legend 
A good time to plant polygonums
Possibly ok, but a risky time to plant polygonums
Probably not a good time to plant polygonums

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. Any later than that and your polygonums may not have a chance to fully mature. Starting your polygonums indoors is a great way to get them started a few weeks earlier.

Last Frost Date

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

Since the USDA zone info for Washington is just an average the actual date of last frost can change quite a bit from year to year. Half of the time in Washington there is a last frost after April 15 so always be ready to cover your polygonums in the event of one of those late frosts.

USDA Zone Info for Washington

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 Washington

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