Before planting it is a good idea to find your USDA Zone info to estimate 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.

A common way of making a decision about when it's a good idea to plant watercress is to examine the USDA zone info for Tualatin.

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 a tiny bit of cold which means that you can plant them just a tiny bit earlier in the year than more sensitive plants.

The earliest that you can plant watercress in Tualatin 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. You can get started a few weeks earlier by starting your watercress indoors.

Last Frost Date

In Tualatin the average date of last frost happens on March 15. In the coldest months of winter you should expect an average low temperature of 15°F.

Remember that USDA zone info for Tualatin is an average and the actual date of last frost can change quite a bit from year to year. Since half of the time in Tualatin there is a last frost after March 15 be ready to cover your watercress in the event of a late frost.

USDA Zone Info for Tualatin

Here is the info for USDA Zone 8b.

Average Date of Last Frost (spring)	March 15
Average Date of First Frost (fall)	November 15
Lowest Expected Low	15°F
Highest Expected Low	20°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 20°F.

Plants to Grow in Tualatin

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