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

By checking out the USDA zone info for Willmar you will be able to determine when it's a good idea to plant polygonums.

Planting Calendar for Polygonums

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

It's a bad idea to plant polygonums until after the last frost because they require warm weather.

The earliest that you can plant polygonums in Willmar is May. However, you really should wait until June 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. If you wait any later than that and your polygonums may not have a chance to fully mature. You can get started a little bit earlier by starting your polygonums indoors.

Last Frost Date

On average the last frost when the weather gets warmer is on May 15 in Willmar. It might get as low as -25°F during the coldest months of winter.

Since the USDA zone info for Willmar is just an average the actual date of last frost is different every year. Half of the time in Willmar last frost occurs after May 15 so make sure that you are ready to protect your polygonums if you have one of those late frosts.

USDA Zone Info for Willmar

Here is the info for USDA Zone 4b.

Average Date of Last Frost (spring)	May 15
Average Date of First Frost (fall)	September 15
Lowest Expected Low	-25°F
Highest Expected Low	-20°F

This means that on a really cold year, the coldest it will get is -25°F. On most years you should be prepared to experience lows near -20°F.

Plants to Grow in Willmar

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