One of the best tools that you have as gardeners to help us determine 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.

The earliest that you can plant blue throatwort in Zone 4a can be determined by reviewing the USDA zone info.

Planting Calendar for Blue Throatwort

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

Since blue throatwort do not do well in cold weather you must wait until after the last frost has passed before you can plant them.

The earliest that you can plant blue throatwort 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 blue throatwort and expect a good harvest is probably August. If you wait any later than that and your blue throatwort may not have a chance to grow to maturity. Starting your blue throatwort indoors is a great way to get them started a few weeks earlier.

Last Frost Date

On average the last frost when the weather gets warmer is on May 15 in Zone 4a. In the coldest months of winter you can expect an average low temperature of -30°F.

Remember that USDA zone info for Zone 4a is just an average 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 cover your blue throatwort in the event of a surprise late frost.

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.