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

In Grinnell you can figure out when it's possible to plant dahlia by looking at the USDA zone info.

Planting Calendar for Dahlia

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

You should not plant dahlia until after the last frost when the weather gets warmer because they are not cold tolerant.

The earliest that you can plant dahlia in Grinnell 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 dahlia and expect a good harvest is probably August. You probably don't want to wait any later than that or else your dahlia may not have a chance to really do well. You can get started a little bit earlier by starting your dahlia indoors.

Last Frost Date

In Grinnell the average date of last frost happens on April 15. You should expect an average low temperature of -20°F in the coldest months of winter.

Remember that the actual date of last frost is not always accurate because it is based on the USDA zone info for Grinnell and it will vary from year to year. Since half of the time in Grinnell last frost occurs after April 15 be ready to cover your dahlia if you have a late frost.

USDA Zone Info for Grinnell

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 Grinnell

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