One of the first steps you take when you are determining your gardening schedule is find your 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.

The USDA zone info for Grinnell can be reffered to in order to figure out when you can plant zinnia.

Planting Calendar for Zinnia

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

Since zinnia do not do well in cold weather you need to wait until after the last frost before you can plant them.

The earliest that you can plant zinnia 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 zinnia and expect a good harvest is probably August. Any later than that and your zinnia may not have a chance to grow to maturity. Starting your zinnia indoors is a great way to get them started a few weeks earlier.

Last Frost Date

On average all chance of frost has passed is on April 15 in Grinnell. In the coldest months of winter you should expect an average low temperature of -20°F.

It's important to 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 changes from year to year. Half of the time in Grinnell there is a last frost after April 15 so just be sure to be ready to cover your zinnia in the event of one of those late frosts.

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.