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.

In Alton you can determine when you can plant blue throatwort by checking out 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.

Blue Throatwort are not cold tolerant which means that it is important to wait until it warms up after the last frost when the weather gets warmer before you can plant them.

The earliest that you can plant blue throatwort in Alton 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 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 really do well. If you are starting your blue throatwort indoors then you might be able to get away with starting them a few weeks earlier.

Last Frost Date

The average date of last frost is April 15 in Alton. In the coldest months of winter you can expect an average low temperature of -10°F.

Since the USDA zone info for Alton is just an average the actual date of last frost will vary from year to year. Since half of the time in Alton there is a last frost after April 15 be ready to cover your blue throatwort in the event of one of those late frosts.

USDA Zone Info for Alton

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 Alton

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