One of the first steps you take when you are getting a good idea your gardening schedule is find your USDA Zone info. The zone info helps tell us things like average date of last frost and lowest expected temperature for your area.

A way of making a decision about when it's a good idea to plant ageratum is to consult the USDA zone info for Lewiston.

Planting Calendar for Ageratum

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

Since ageratum are not cold tolerant it is necessary to wait until after the last frost has passed before you can plant them.

The earliest that you can plant ageratum in Lewiston 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. You can get started a few weeks earlier by starting your ageratum indoors.

Last Frost Date

On average the last frost has passed is on April 15 in Lewiston. In the coldest months of winter you should expect an average low temperature of -15°F.

Since the USDA zone info for Lewiston is an average the actual date of last frost changes from year to year. Half of the time in Lewiston last frost occurs after April 15 so make sure that you are ready to cover your ageratum if you have one of those late frosts.

USDA Zone Info for Lewiston

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 Lewiston

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