One of the best tools that you have as gardeners to help us figure out 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.

The USDA zone info for National City can be read to estimate when you can 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.

Watercress are barely cold tolerant which tells us that you can get them planted just a bit earlier than more sensitive plants.

The earliest that you can plant watercress in National City 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 watercress and expect a good harvest is probably September. If you wait any later than that and your watercress may not have a chance to fully mature. You can get started a couple of weeks earlier by starting your watercress indoors.

Last Frost Date

In National City the average date of last frost happens on January 31. It might get as low as 35°F during the coldest months of winter.

It's important to remember that USDA zone info for National City may not be accurate from year to year and the actual date of last frost will vary from year to year. Since half of the time in National City last frost occurs after January 31 be ready to protect your watercress in the event of one of those late frosts.

USDA Zone Info for National City

Here is the info for USDA Zone 10b.

Average Date of Last Frost (spring)	January 31
Average Date of First Frost (fall)	December 15
Lowest Expected Low	35°F
Highest Expected Low	40°F

This means that on a really cold year, the coldest it will get is 35°F. On most years you should be prepared to experience lows near 40°F.

Plants to Grow in National City

You may be interested in your other planting guides for National City.