One of the best tools that you have as gardeners to help us determine 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 USDA zone info for Marengo should be reviewed to determine when it's possible to plant ageratum.

Planting Calendar for Ageratum

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

Ageratum do not do well in cold weather which tells us that you need to wait until it warms up after the last frost has passed before you can plant them.

The earliest that you can plant ageratum in Marengo 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. You probably don't want to wait any later than that or else your ageratum may not have a chance to fully mature. You can get started a few weeks earlier by starting your ageratum indoors.

Last Frost Date

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

Since the USDA zone info for Marengo may not be accurate from year to year the actual date of last frost changes from year to year. Since half of the time in Marengo you get a frost after April 15 be ready to protect your ageratum in the event of a late frost.

USDA Zone Info for Marengo

Here is the info for USDA Zone 5b.

Average Date of Last Frost (spring)	April 15
Average Date of First Frost (fall)	October 15
Lowest Expected Low	-15°F
Highest Expected Low	-10°F

This means that on a really cold year, the coldest it will get is -15°F. On most years you should be prepared to experience lows near -10°F.

Plants to Grow in Marengo

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