Before planting it is a good idea to find your USDA Zone info to figure out 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.

The USDA zone info for Island Lake can be looked at to figure out when it's a good idea to plant periwinkles.

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 Island Lake 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. If you wait any later than that and your periwinkles may not have a chance to fully mature. You can get started a couple of weeks earlier by starting your periwinkles indoors.

Last Frost Date

On average the last frost has passed is on April 15 in Island Lake. It might get as low as -15°F during the coldest months of winter.

Remember that USDA zone info for Island Lake is just an average and the actual date of last frost changes from year to year. Half of the time in Island Lake it frosts late in the year after April 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 Island Lake

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 Island Lake

You may be interested in your other planting guides for Island Lake.