One of the best tools that you have as gardeners to help us figure out your gardening schedule is the USDA zone info. The zone info helps tell us things like average date of last frost and lowest expected temperature for your area.

A way of estimating when it's the best time to plant violas is to use the USDA zone info for Coralville.

Planting Calendar for Violas

Frost tolerance for violas:	Very tolerant of frost.
When to plant:	Up to 7 weeks before last frost.

Violas tend to make it in a bit of cold which means that you can plant them a lot earlier in the year than other frost tender plants.

The earliest that you can plant violas in Coralville is February. However, you really should wait until March if you don't want to take any chances.

The last month that you can plant violas and expect a good harvest is probably September. You probably don't want to wait any later than that or else your violas may not have a chance to really do well. If you are starting your violas indoors then you might be able to get away with starting them a couple of weeks earlier.

Last Frost Date

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

Just be sure to remember that the actual date of last frost is just an average because it is based on the USDA zone info for Coralville and it changes from year to year. Half of the time in Coralville it frosts late in the year after April 15 so make sure that you are ready to cover your violas if you have one of those late frosts.

USDA Zone Info for Coralville

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 Coralville

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