One of the first steps you take when you are getting a good idea 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 USDA zone info for Charleston should be reviewed to figure out when it's a good idea to plant watercress.

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.

Since watercress are barely cold tolerant you can plant them slightly earlier in the year than other plants that might not handle the cold.

The earliest that you can plant watercress in Charleston 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 grow to maturity. If you are starting your watercress indoors then you might be able to get away with starting them a couple of weeks earlier.

Last Frost Date

In Charleston the average date of last frost happens on April 15. It might get as low as 0°F during the coldest months of winter.

Since the USDA zone info for Charleston is not always accurate the actual date of last frost changes from year to year. Since half of the time in Charleston it frosts late in the year after April 15 be ready to cover your watercress in the event of one of those late frosts.

USDA Zone Info for Charleston

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 Charleston

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