One of the best tools that you have as gardeners to help us figure out 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 estimate when it's a good idea to plant sweet potatos by referring to the USDA zone info for Washington.

Planting Calendar for Sweet Potatos

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

Sweet Potatos require warm weather which tells us that you need to wait until it warms up after the last frost before you can plant them.

The earliest that you can plant sweet potatos 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 sweet potatos and expect a good harvest is probably August. Any later than that and your sweet potatos may not have a chance to grow to maturity. You can get started a couple of weeks earlier by starting your sweet potatos indoors.

Last Frost Date

In Washington the average date of last frost happens on April 15. In the coldest months of winter you can expect an average low temperature of -10°F.

Always keep in mind that USDA zone info for Washington is not always accurate and the actual date of last frost is different every year. Since half of the time in Washington you get a frost after April 15 be ready to cover your sweet potatos if you have a surprise late frost.

USDA Zone Info for Washington

Here is the info for USDA Zone 6a.

Average Date of Last Frost (spring)	April 15
Average Date of First Frost (fall)	October 15
Lowest Expected Low	-10°F
Highest Expected Low	-5°F

This means that on a really cold year, the coldest it will get is -10°F. On most years you should be prepared to experience lows near -5°F.

Plants to Grow in Washington

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