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 it's the best time to plant ageratum by reviewing the USDA zone info.

Planting Calendar for Ageratum

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

You should not plant ageratum until after the last frost when the weather gets warmer because they do not do well in cold weather.

The earliest that you can plant ageratum 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 ageratum and expect a good harvest is probably August. If you wait any later than that and your ageratum may not have a chance to grow to maturity. You can get started a little bit earlier by starting your ageratum indoors.

Last Frost Date

On average the last frost when the weather gets warmer is on April 15 in Alton. You can expect an average low temperature of -10°F in the coldest months of winter.

Remember that USDA zone info for Alton is just an average and 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 protect your ageratum 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.