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.

The earliest that you can plant rock cress in Philadelphia should be figured out by looking at the USDA zone info.

Planting Calendar for Rock Cress

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

You can plant rock cress earlier in the year because they do well in cold.

The earliest that you can plant rock cress 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 rock cress and expect a good harvest is probably September. Any later than that and your rock cress may not have a chance to fully mature. Starting your rock cress indoors is a great way to get them started a little bit earlier.

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.

Since the USDA zone info for Philadelphia is not always accurate the actual date of last frost will vary from year to year. Half of the time in Philadelphia there is a last frost after March 15 so just be sure to be ready to protect your rock cress if you have a 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.