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 looking at the USDA zone info for Zone 4a it's possible to determine when it's possible to plant bidens.

Planting Calendar for Bidens

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

Since bidens require warm weather you need to wait until after all chance of frost has passed before you can plant them.

The earliest that you can plant bidens in Zone 4a 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 bidens and expect a good harvest is probably August. You probably don't want to wait any later than that or else your bidens may not have a chance to really do well. If you are starting your bidens indoors then you might be able to get away with starting them a little bit earlier.

Last Frost Date

The average date of last frost is May 15 in Zone 4a. You can expect an average low temperature of -30°F in the coldest months of winter.

Always keep in mind that USDA zone info for Zone 4a may not be accurate from year to year and the actual date of last frost will vary from year to year. Since half of the time in Zone 4a you get a frost after May 15 be ready to protect your bidens in the event of one of those late frosts.

USDA Zone Info for Zone 4a

Here is the info for USDA Zone 4a.

Average Date of Last Frost (spring)	May 15
Average Date of First Frost (fall)	September 15
Lowest Expected Low	-30°F
Highest Expected Low	-25°F

This means that on a really cold year, the coldest it will get is -30°F. On most years you should be prepared to experience lows near -25°F.

Plants to Grow in Zone 4a

You may be interested in your other planting guides for Zone 4a.