One of the best tools that you have as gardeners to help us estimate your gardening schedule is the USDA zone info. The most important data that the zone info tells us is average last frost and the lowest expected temperature for your area.

You should be able to figure out when to plant polygonums by reviewing the USDA zone info for Portland.

Planting Calendar for Polygonums

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

Since polygonums require warm weather it's necessary to wait until after the last frost when the weather gets warmer before you can plant them.

The earliest that you can plant polygonums in 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. If you wait 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 couple of weeks earlier.

Last Frost Date

In Portland 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 the actual date of last frost is an average because it is based on the USDA zone info for Portland and it will vary from year to year. Since half of the time in Portland last frost occurs after April 15 be ready to cover your polygonums if you have one of those late frosts.

USDA Zone Info for Portland

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 Portland

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