One of the first steps you take when you are getting a good idea your gardening schedule is find your USDA Zone info. The zone info helps tell us things like average date of last frost and lowest expected temperature for your area.

One way of figuring out when you can plant periwinkles is to look at the USDA zone info for Crystal City.

Planting Calendar for Periwinkles

Frost tolerance for periwinkles:	Not tolerant of frost.
When to plant:	After the last frost.

Periwinkles do not do well in cold weather which means that you have to wait until it warms up after the last frost before you can plant them.

The earliest that you can plant periwinkles in Crystal City 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 periwinkles and expect a good harvest is probably September. Any later than that and your periwinkles may not have a chance to really do well. You can get started a few weeks earlier by starting your periwinkles indoors.

Last Frost Date

On average the last frost when the weather gets warmer is on February 15 in Crystal City. In the coldest months of winter you should expect an average low temperature of 20°F.

Since the USDA zone info for Crystal City is not always accurate the actual date of last frost will vary from year to year. Half of the time in Crystal City you get surprised by a frost after February 15 so just be sure to be ready to protect your periwinkles in the event of one of those late frosts.

USDA Zone Info for Crystal City

Here is the info for USDA Zone 9a.

Average Date of Last Frost (spring)	February 15
Average Date of First Frost (fall)	December 15
Lowest Expected Low	20°F
Highest Expected Low	25°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 25°F.

Plants to Grow in Crystal City

You may be interested in your other planting guides for Crystal City.