Before planting it is a good idea to find your USDA Zone info to estimate your garden schedule. The most important data that the zone info tells us is average last frost and the lowest expected temperature for your area.

You should be able to determine when it's the best time to plant periwinkles by referring to the USDA zone info for Rockton.

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 when the weather gets warmer before you can plant them.

The earliest that you can plant periwinkles in Rockton 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. Any later than that and your periwinkles may not have a chance to fully mature. If you are starting your periwinkles indoors then you might be able to get away with starting them a few weeks earlier.

Last Frost Date

The average date of last frost is April 15 in Rockton. You can expect an average low temperature of -15°F in the coldest months of winter.

Remember that USDA zone info for Rockton may not be accurate from year to year and the actual date of last frost changes from year to year. Half of the time in Rockton you get surprised by a frost after April 15 so be sure to be ready to cover your periwinkles if you have a surprise late frost.

USDA Zone Info for Rockton

Here is the info for USDA Zone 5b.

Average Date of Last Frost (spring)	April 15
Average Date of First Frost (fall)	October 15
Lowest Expected Low	-15°F
Highest Expected Low	-10°F

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

Plants to Grow in Rockton

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