One of the first steps you take when you are estimating your gardening schedule is find your 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.

The first opportunity to plant watercress in Phoenix should be figured out by using the USDA zone info.

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.

You can plant watercress slightly earlier in the year because they do ok in moderate cold.

The earliest that you can plant watercress in Phoenix 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. If you wait any later than that and your watercress may not have a chance to fully mature. You can get started a little bit earlier by starting your watercress indoors.

Last Frost Date

In Phoenix the average date of last frost happens on March 15. In the coldest months of winter you should expect an average low temperature of 10°F.

It's important to 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 Phoenix and it can change quite a bit from year to year. Half of the time in Phoenix you get a frost after March 15 so make sure that you are ready to protect your watercress in the event of a surprise late frost.

USDA Zone Info for Phoenix

Here is the info for USDA Zone 8a.

Average Date of Last Frost (spring)	March 15
Average Date of First Frost (fall)	November 15
Lowest Expected Low	10°F
Highest Expected Low	15°F

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

Plants to Grow in Phoenix

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