The USDA Zone info is a great tool for gardeners to help us determine your gardening schedule. The zone info helps tell us things like average date of last frost and lowest expected temperature for your area.

The USDA zone info for Watertown can be looked at to estimate when it's possible to plant flower-of-an-hour.

Planting Calendar for Flower-of-an-Hour

Frost tolerance for flower-of-an-hour:	Tolerant of a very small amount of frost.
When to plant:	Up to 3 weeks before last frost.

Flower-of-an-Hour can survive in a tiny bit of cold which tells us that you can plant them slightly earlier in the year than other frost tender plants.

The earliest that you can plant flower-of-an-hour in Watertown is April. However, you really should wait until May if you don't want to take any chances.

The last month that you can plant flower-of-an-hour and expect a good harvest is probably August. If you wait any later than that and your flower-of-an-hour may not have a chance to really do well. If you are starting your flower-of-an-hour indoors then you might be able to get away with starting them a little bit earlier.

Last Frost Date

In Watertown the average date of last frost happens on May 15. It might get as low as -25°F during the coldest months of winter.

Keep in mind that the actual date of last frost is just an average because it is based on the USDA zone info for Watertown and it is different every year. Since half of the time in Watertown it frosts late in the year after May 15 be ready to cover your flower-of-an-hour in the event of one of those late frosts.

USDA Zone Info for Watertown

Here is the info for USDA Zone 4b.

Average Date of Last Frost (spring)	May 15
Average Date of First Frost (fall)	September 15
Lowest Expected Low	-25°F
Highest Expected Low	-20°F

This means that on a really cold year, the coldest it will get is -25°F. On most years you should be prepared to experience lows near -20°F.

Plants to Grow in Watertown

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