Before planting it is a good idea to find your USDA Zone info to determine your garden schedule. 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 Seattle can be reviewed to estimate when you can 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 require warm weather which means that it is important 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 Seattle 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 fully mature. If you are starting your ageratum indoors then you might be able to get away with starting them a little bit earlier.

Last Frost Date

The average date of last frost is March 15 in Seattle. You can expect an average low temperature of 15°F in the coldest months of winter.

Always keep in mind that the actual date of last frost is not always accurate because it is based on the USDA zone info for Seattle and it is different every year. Since half of the time in Seattle you get a frost after March 15 be ready to cover your ageratum in the event of a late frost.

USDA Zone Info for Seattle

Here is the info for USDA Zone 8b.

Average Date of Last Frost (spring)	March 15
Average Date of First Frost (fall)	November 15
Lowest Expected Low	15°F
Highest Expected Low	20°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 20°F.

Plants to Grow in Seattle

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