One of the best tools that you have as gardeners to help us estimate 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.

In Decorah you can estimate when it's the best time to plant dahlias by reviewing the USDA zone info.

Planting Calendar for Dahlias

Frost tolerance for dahlias:	Not tolerant of frost.
When to plant:	After the last frost when the weather gets warmer.

Since dahlias are not cold tolerant you have to wait until after the last frost before you can plant them.

The earliest that you can plant dahlias in Decorah is May. However, you really should wait until June if you don't want to take any chances.

The last month that you can plant dahlias and expect a good harvest is probably August. If you wait any later than that and your dahlias may not have a chance to grow to maturity. Starting your dahlias indoors is a great way to get them started a little bit earlier.

Last Frost Date

In Decorah the average date of last frost happens on May 15. In the coldest months of winter you can expect an average low temperature of -25°F.

Just be sure to remember that USDA zone info for Decorah is not always accurate and the actual date of last frost will vary from year to year. Since half of the time in Decorah you get surprised by a frost after May 15 be ready to protect your dahlias in the event of one of those late frosts.

USDA Zone Info for Decorah

Here is the info for USDA Zone 4b.

Average Date of Last Frost (spring)	May 15
Average Date of First Frost (fall)	September 15
Lowest Expected Low	-25°F
Highest Expected Low	-20°F

This means that on a really cold year, the coldest it will get is -25°F. On most years you should be prepared to experience lows near -20°F.

Plants to Grow in Decorah

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