Before planting it is a good idea to find your USDA Zone info to estimate 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.

One way of figuring out when it's a good idea to plant sweet potatos is to refer to the USDA zone info for Mercer Island.

Planting Calendar for Sweet Potatos

Frost tolerance for sweet potatos:	Not tolerant of frost.
When to plant:	After the last frost when the weather gets warmer.

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

The earliest that you can plant sweet potatos in Mercer Island 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. You probably don't want to wait any later than that or else your sweet potatos may not have a chance to fully mature. If you are starting your sweet potatos indoors then you might be able to get away with starting them a few weeks earlier.

Last Frost Date

In Mercer Island the average date of last frost happens on March 15. It might get as low as 15°F during the coldest months of winter.

It's important to remember that the actual date of last frost may not be accurate from year to year because it is based on the USDA zone info for Mercer Island and it is different every year. Half of the time in Mercer Island last frost occurs after March 15 so always be ready to protect your sweet potatos if you have one of those late frosts.

USDA Zone Info for Mercer Island

Here is the info for USDA Zone 8b.

Average Date of Last Frost (spring)	March 15
Average Date of First Frost (fall)	November 15
Lowest Expected Low	15°F
Highest Expected Low	20°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 20°F.

Plants to Grow in Mercer Island

You may be interested in your other planting guides for Mercer Island.