One of the first steps you take when you are figuring out 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.

One way of estimating when it's possible to plant periwinkles is to use the USDA zone info for Rockville.

Planting Calendar for Periwinkles

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

It's probably not a good idea to plant periwinkles until after the last frost because they do not do well in cold weather.

The earliest that you can plant periwinkles in Rockville 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 periwinkles and expect a good harvest is probably August. You probably don't want to wait any later than that or else your periwinkles may not have a chance to grow to maturity. You can get started a couple of weeks earlier by starting your periwinkles indoors.

Last Frost Date

On average all chance of frost has passed is on April 15 in Rockville. In the coldest months of winter you can expect an average low temperature of 0°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 Rockville and it can change quite a bit from year to year. Since half of the time in Rockville you get a frost after April 15 be ready to cover your periwinkles in the event of one of those late frosts.

USDA Zone Info for Rockville

Here is the info for USDA Zone 7a.

Average Date of Last Frost (spring)	April 15
Average Date of First Frost (fall)	October 15
Lowest Expected Low	0°F
Highest Expected Low	5°F

This means that on a really cold year, the coldest it will get is 0°F. On most years you should be prepared to experience lows near 5°F.

Plants to Grow in Rockville

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