One of the best tools that you have as gardeners to help us figure out your gardening schedule is the USDA zone info. The zone info helps tell us things like average date of last frost and lowest expected temperature for your area.

The first opportunity to plant heliotrope in Alton should be determined by reviewing the USDA zone info.

Planting Calendar for Heliotrope

Frost tolerance for heliotrope:	Not tolerant of frost.
When to plant:	After all chance of frost has passed.

Heliotrope are not cold tolerant which means that you must wait until it warms up after the last frost before you can plant them.

The earliest that you can plant heliotrope 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 heliotrope and expect a good harvest is probably August. Any later than that and your heliotrope may not have a chance to really do well. You can get started a little bit earlier by starting your heliotrope indoors.

Last Frost Date

On average the last frost has passed is on April 15 in Alton. In the coldest months of winter you should 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 can change quite a bit from year to year. Since half of the time in Alton you get a frost after April 15 be ready to cover your heliotrope if you have a late frost.

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.