The USDA Zone info is a great tool for gardeners to help us figure out your gardening 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 Portland can be read to determine when 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 very little cold which tells us that you can plant them just a tiny bit earlier in the year than plants that are more sensitive to the cold.

The earliest that you can plant watercress in Portland 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 really do well. If you are starting your watercress indoors then you might be able to get away with starting them a few weeks earlier.

Last Frost Date

On average all chance of frost has passed is on April 15 in Portland. In the coldest months of winter you should expect an average low temperature of -15°F.

Since the USDA zone info for Portland may not be accurate from year to year the actual date of last frost changes from year to year. Half of the time in Portland you get a frost after April 15 so make sure that you are ready to protect your watercress if you have one of those late frosts.

USDA Zone Info for Portland

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 Portland

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