One of the first steps you take when you are getting a good idea your gardening schedule is find your USDA Zone info. The most important data that the zone info tells us is average last frost and the lowest expected temperature for your area.

One way of determining when to plant calendula is to look at 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 well in mild cold which tells us that you can plant them a little bit earlier in the year than other plants that might not handle 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. If you wait any later than that and your calendula may not have a chance to really do well. You can get started a little bit earlier by starting your calendula indoors.

Last Frost Date

The average date of last frost is April 15 in Philadelphia. In the coldest months of winter you can expect an average low temperature of 0°F.

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 Philadelphia and it will vary from year to year. Half of the time in Philadelphia you get a frost after April 15 so always be ready to cover your calendula if you have a surprise late frost.

USDA Zone Info for Philadelphia

Here is the info for USDA Zone 7a.

Average Date of Last Frost (spring)	April 15
Average Date of First Frost (fall)	October 15
Lowest Expected Low	0°F
Highest Expected Low	5°F

This means that on a really cold year, the coldest it will get is 0°F. On most years you should be prepared to experience lows near 5°F.

Plants to Grow in Philadelphia

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