One of the best tools that you have as gardeners to help us estimate your gardening schedule is the USDA zone info. The zone info helps tell us things like average date of last frost and lowest expected temperature for your area.

You should be able to determine when it's a good idea to plant watercress by referring to the USDA zone info for Charleston.

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 tend to make it in very little cold which tells us that 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. You probably don't want to wait any later than that or else your watercress may not have a chance to grow to maturity. Starting your watercress indoors is a great way to get them started a couple of weeks earlier.

Last Frost Date

The average date of last frost is April 15 in Charleston. In the coldest months of winter you can expect an average low temperature of -10°F.

Since the USDA zone info for Charleston may not be accurate from year to year the actual date of last frost changes from year to year. Half of the time in Charleston last frost occurs after April 15 so make sure that you are prepared to protect your watercress in the event of a surprise late frost.

USDA Zone Info for Charleston

Here is the info for USDA Zone 6a.

Average Date of Last Frost (spring)	April 15
Average Date of First Frost (fall)	October 15
Lowest Expected Low	-10°F
Highest Expected Low	-5°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 -5°F.

Plants to Grow in Charleston

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