One of the first steps you take when you are estimating your gardening schedule is find your USDA Zone info. The zone info helps tell us things like average date of last frost and lowest expected temperature for your area.

The first opportunity to plant watercress in Philadelphia should be determined by using 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.

Watercress do ok in a tiny bit of cold which tells us that you can plant them just a tiny bit earlier in the year than other frost tender plants.

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 really do well. You can get started a couple of weeks earlier by starting your watercress indoors.

Last Frost Date

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

Remember that USDA zone info for Philadelphia is just an average and the actual date of last frost will vary from year to year. Since half of the time in Philadelphia it frosts late in the year after March 15 be ready to protect your watercress in the event of 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.