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 referring to the USDA zone info for Zone 3a you should be able to estimate when to plant scarlet runner beans.

Planting Calendar for Scarlet Runner Beans

Frost tolerance for scarlet runner beans:	Not tolerant of frost.
When to plant:	After the last frost when the weather gets warmer.

Since scarlet runner beans require warm weather it's necessary to wait until after the last frost before you can plant them.

The earliest that you can plant scarlet runner beans in Zone 3a 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 scarlet runner beans and expect a good harvest is probably August. You probably don't want to wait any later than that or else your scarlet runner beans may not have a chance to really do well. Starting your scarlet runner beans indoors is a great way to get them started a little bit earlier.

Last Frost Date

In Zone 3a the average date of last frost happens on May 15. You can expect an average low temperature of -40°F in the coldest months of winter.

Always keep in mind that the actual date of last frost is just an average because it is based on the USDA zone info for Zone 3a and it is different every year. Half of the time in Zone 3a last frost occurs after May 15 so just be sure to be ready to protect your scarlet runner beans in the event of a late frost.

USDA Zone Info for Zone 3a

Here is the info for USDA Zone 3a.

Average Date of Last Frost (spring)	May 15
Average Date of First Frost (fall)	September 15
Lowest Expected Low	-40°F
Highest Expected Low	-35°F

This means that on a really cold year, the coldest it will get is -40°F. On most years you should be prepared to experience lows near -35°F.

Plants to Grow in Zone 3a

You may be interested in your other planting guides for Zone 3a.