Before planting it is a good idea to find your USDA Zone info to determine your garden schedule. The most important data that the zone info tells us is average last frost and the lowest expected temperature for your area.

The USDA zone info for Janesville can be reviewed to determine 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.

Watercress do ok in mild cold which tells us that you can plant them a bit earlier in the year than plants that are more sensitive to the cold.

The earliest that you can plant watercress in Janesville 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 little bit earlier.

Last Frost Date

In Janesville the average date of last frost happens on April 15. It might get as low as -20°F during the coldest months of winter.

Remember that the actual date of last frost may not be accurate from year to year because it is based on the USDA zone info for Janesville and it can change quite a bit from year to year. Half of the time in Janesville you get a frost after April 15 so just be sure to be ready to cover your watercress if you have a surprise late frost.

USDA Zone Info for Janesville

Here is the info for USDA Zone 5a.

Average Date of Last Frost (spring)	April 15
Average Date of First Frost (fall)	October 15
Lowest Expected Low	-20°F
Highest Expected Low	-15°F

This means that on a really cold year, the coldest it will get is -20°F. On most years you should be prepared to experience lows near -15°F.

Plants to Grow in Janesville

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