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

In Marshalltown you can estimate when it's the best time to plant ageratum by using the USDA zone info.

Planting Calendar for Ageratum

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

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

The earliest that you can plant ageratum in Marshalltown 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. Any later than that and your ageratum may not have a chance to fully mature. Starting your ageratum indoors is a great way to get them started a couple of weeks earlier.

Last Frost Date

The average date of last frost is April 15 in Marshalltown. You can expect an average low temperature of -20°F in the coldest months of winter.

Since the USDA zone info for Marshalltown is an average the actual date of last frost is different every year. Half of the time in Marshalltown last frost occurs after April 15 so make sure that you are ready to protect your ageratum if you have a surprise late frost.

USDA Zone Info for Marshalltown

Here is the info for USDA Zone 5a.

Average Date of Last Frost (spring)	April 15
Average Date of First Frost (fall)	October 15
Lowest Expected Low	-20°F
Highest Expected Low	-15°F

This means that on a really cold year, the coldest it will get is -20°F. On most years you should be prepared to experience lows near -15°F.

Plants to Grow in Marshalltown

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