One of the best tools that you have as gardeners to help us determine your gardening schedule is the 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.

You should be able to estimate when to plant periwinkles by reviewing the USDA zone info for Tiffin.

Planting Calendar for Periwinkles

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

It's a bad idea to plant periwinkles until after all chance of frost has passed because they require warm weather.

The earliest that you can plant periwinkles in Tiffin 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. Starting your periwinkles indoors is a great way to get them started a couple of weeks earlier.

Last Frost Date

In Tiffin the average date of last frost happens on April 15. In the coldest months of winter you can expect an average low temperature of -10°F.

Since the USDA zone info for Tiffin is an average the actual date of last frost can change quite a bit from year to year. Since half of the time in Tiffin it frosts late in the year after April 15 be ready to protect your periwinkles if you have one of those late frosts.

USDA Zone Info for Tiffin

Here is the info for USDA Zone 6a.

Average Date of Last Frost (spring)	April 15
Average Date of First Frost (fall)	October 15
Lowest Expected Low	-10°F
Highest Expected Low	-5°F

This means that on a really cold year, the coldest it will get is -10°F. On most years you should be prepared to experience lows near -5°F.

Plants to Grow in Tiffin

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