Before planting it is a good idea to find your USDA Zone info to figure out 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.

You will be able to estimate when to plant liatris by referring to the USDA zone info for Philadelphia.

Planting Calendar for Liatris

Frost tolerance for liatris:	Very tolerant of frost.
When to plant:	Up to 7 weeks before last frost.

Liatris do well in cold which means that you can get them planted much earlier than plants that are more sensitive to the cold.

The earliest that you can plant liatris in Philadelphia is February. However, you really should wait until March if you don't want to take any chances.

The last month that you can plant liatris and expect a good harvest is probably September. Any later than that and your liatris may not have a chance to grow to maturity. You can get started a few weeks earlier by starting your liatris indoors.

Last Frost Date

The average date of last frost is March 15 in Philadelphia. It might get as low as 10°F during the coldest months of winter.

Always keep in mind that the actual date of last frost is an average because it is based on the USDA zone info for Philadelphia and it can change quite a bit from year to year. Half of the time in Philadelphia there is a last frost after March 15 so always be ready to cover your liatris if you have a surprise late frost.

USDA Zone Info for Philadelphia

Here is the info for USDA Zone 8a.

Average Date of Last Frost (spring)	March 15
Average Date of First Frost (fall)	November 15
Lowest Expected Low	10°F
Highest Expected Low	15°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 15°F.

Plants to Grow in Philadelphia

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