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

You will be able to determine when to plant tomatos by looking at the USDA zone info for Grinnell.

Planting Calendar for Tomatos

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

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

The earliest that you can plant tomatos 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 tomatos and expect a good harvest is probably August. If you wait any later than that and your tomatos may not have a chance to really do well. If you are starting your tomatos 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 Grinnell. In the coldest months of winter you should expect an average low temperature of -20°F.

Always keep in mind that USDA zone info for Grinnell is just an average and the actual date of last frost is different every year. Half of the time in Grinnell there is a last frost after April 15 so make sure that you are prepared to protect your tomatos in the event of 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.