The USDA Zone info is a great tool for gardeners to help us figure out your gardening schedule. The most important data that the zone info tells us is average last frost and the lowest expected temperature for your area.

A way of making a decision about when it's possible to plant periwinkles is to examine the USDA zone info for Iowa Falls.

Planting Calendar for Periwinkles

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

You really shouldn't plant periwinkles until after the last frost because they do not do well in cold weather.

The earliest that you can plant periwinkles in Iowa Falls 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 fully mature. If you are starting your periwinkles indoors then you might be able to get away with starting them a couple of weeks earlier.

Last Frost Date

On average all chance of frost has passed is on April 15 in Iowa Falls. It might get as low as -20°F during the coldest months of winter.

Just be sure to remember that the actual date of last frost is not always accurate because it is based on the USDA zone info for Iowa Falls and it will vary from year to year. Half of the time in Iowa Falls you get 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 Iowa Falls

Here is the info for USDA Zone 5a.

Average Date of Last Frost (spring)	April 15
Average Date of First Frost (fall)	October 15
Lowest Expected Low	-20°F
Highest Expected Low	-15°F

This means that on a really cold year, the coldest it will get is -20°F. On most years you should be prepared to experience lows near -15°F.

Plants to Grow in Iowa Falls

You may be interested in your other planting guides for Iowa Falls.