One of the best tools that you have as gardeners to help us determine your gardening schedule is the USDA zone info. The most important data that the zone info tells us is average last frost and the lowest expected temperature for your area.

You should be able to figure out when it's the best time to plant watercress by looking at the USDA zone info for Wilmette.

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 well in some cold which tells us that you can plant them slightly earlier in the year than more sensitive plants.

The earliest that you can plant watercress in Wilmette 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. You can get started a couple of weeks earlier by starting your watercress indoors.

Last Frost Date

The average date of last frost is April 15 in Wilmette. You should expect an average low temperature of -15°F in the coldest months of winter.

Since the USDA zone info for Wilmette may not be accurate from year to year the actual date of last frost can change quite a bit from year to year. Half of the time in Wilmette last frost occurs after April 15 so just be sure to be ready to cover your watercress if you have a late frost.

USDA Zone Info for Wilmette

Here is the info for USDA Zone 5b.

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

This means that on a really cold year, the coldest it will get is -15°F. On most years you should be prepared to experience lows near -10°F.

Plants to Grow in Wilmette

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