Before planting it is a good idea to find your USDA Zone info to determine 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 looking at the USDA zone info for Thief River Falls it's possible to estimate 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.

Since polygonums are not cold tolerant it's important to wait until after the last frost has passed before you can plant them.

The earliest that you can plant polygonums in Thief River Falls 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. 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 Thief River Falls. You should expect an average low temperature of -35°F in the coldest months of winter.

It's important to remember that USDA zone info for Thief River Falls may not be accurate from year to year and the actual date of last frost changes from year to year. Since half of the time in Thief River Falls last frost occurs after May 15 be ready to protect your polygonums if you have one of those late frosts.

USDA Zone Info for Thief River Falls

Here is the info for USDA Zone 3b.

Average Date of Last Frost (spring)	May 15
Average Date of First Frost (fall)	September 15
Lowest Expected Low	-35°F
Highest Expected Low	-30°F

This means that on a really cold year, the coldest it will get is -35°F. On most years you should be prepared to experience lows near -30°F.

Plants to Grow in Thief River Falls

You may be interested in your other planting guides for Thief River Falls.