Before planting it is a good idea to find your USDA Zone info to estimate your garden schedule. The zone info helps tell us things like average date of last frost and lowest expected temperature for your area.

The first chance to plant periwinkles in Rio Grande City should be estimated by using the USDA zone info.

Planting Calendar for Periwinkles

Frost tolerance for periwinkles:	Not tolerant of frost.
When to plant:	After all chance of frost has passed.

Since periwinkles are not cold tolerant it's necessary to wait until after the last frost has passed before you can plant them.

The earliest that you can plant periwinkles in Rio Grande 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 grow to maturity. You can get started a few weeks earlier by starting your periwinkles indoors.

Last Frost Date

In Rio Grande City the average date of last frost happens on February 15. It might get as low as 25°F during the coldest months of winter.

Since the USDA zone info for Rio Grande City is not always accurate the actual date of last frost changes from year to year. Since half of the time in Rio Grande City last frost occurs after February 15 be ready to protect your periwinkles in the event of a late frost.

USDA Zone Info for Rio Grande City

Here is the info for USDA Zone 9b.

Average Date of Last Frost (spring)	February 15
Average Date of First Frost (fall)	December 15
Lowest Expected Low	25°F
Highest Expected Low	30°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 30°F.

Plants to Grow in Rio Grande City

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