The USDA Zone info is a great tool for gardeners to help us estimate your gardening 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 figure out when you can plant calendula by referring to the USDA zone info for Philadelphia.

Planting Calendar for Calendula

Frost tolerance for calendula:	Tolerant of some frost.
When to plant:	Up to 5 weeks before last frost.

Calendula do ok in mild cold which means that you can plant them a little earlier in the year than plants that are more sensitive to the cold.

The earliest that you can plant calendula 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 calendula and expect a good harvest is probably September. You probably don't want to wait any later than that or else your calendula may not have a chance to grow to maturity. You can get started a couple of weeks earlier by starting your calendula indoors.

Last Frost Date

On average the last frost is on March 15 in Philadelphia. In the coldest months of winter you can expect an average low temperature of 10°F.

Always keep in mind that the actual date of last frost may not be accurate from year to year because it is based on the USDA zone info for Philadelphia and it changes from year to year. Half of the time in Philadelphia you get surprised by a frost after March 15 so make sure that you are ready to protect your calendula in the event of one of those late frosts.

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.