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

In Philadelphia you can figure out when to plant watercress by reviewing the USDA zone info.

Planting Calendar for Watercress

Frost tolerance for watercress:	Tolerant of a very small amount of frost.
When to plant:	Up to 3 weeks before last frost.

You can plant watercress just a tiny bit earlier in the year because they do ok in moderate cold.

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

The last month that you can plant watercress and expect a good harvest is probably August. Any later than that and your watercress may not have a chance to fully mature. If you are starting your watercress indoors then you might be able to get away with starting them a few weeks earlier.

Last Frost Date

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

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 can change quite a bit from year to year. Half of the time in Philadelphia last frost occurs after April 15 so make sure that you are ready to cover your watercress in the event of a 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.