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.

By checking out the USDA zone info for South Portland it's possible to estimate when you can 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 require warm weather you have to wait until after the last frost has passed before you can plant them.

The earliest that you can plant polygonums in South Portland 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. If you are starting your polygonums indoors then you might be able to get away with starting them a few weeks earlier.

Last Frost Date

The average date of last frost is April 15 in South Portland. In the coldest months of winter you should expect an average low temperature of -15°F.

Just be sure to remember that USDA zone info for South Portland is an average and the actual date of last frost can change quite a bit from year to year. Half of the time in South Portland it frosts late in the year after April 15 so just be sure to be ready to cover your polygonums in the event of one of those late frosts.

USDA Zone Info for South 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 South Portland

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