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

You will be able to estimate when you can plant asters by using the USDA zone info for Grinnell.

Planting Calendar for Asters

Frost tolerance for asters:	Tolerant of some frost.
When to plant:	Up to 5 weeks before last frost.

Asters can survive in mild cold which tells us that you can plant them just a bit earlier in the year than other plants that might not handle the cold.

The earliest that you can plant asters in Grinnell 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 asters and expect a good harvest is probably September. You probably don't want to wait any later than that or else your asters may not have a chance to grow to maturity. You can get started a couple of weeks earlier by starting your asters indoors.

Last Frost Date

The average date of last frost is April 15 in Grinnell. In the coldest months of winter you can expect an average low temperature of -20°F.

Just be sure to remember that the actual date of last frost is an average because it is based on the USDA zone info for Grinnell and it is different every year. Half of the time in Grinnell you get surprised by a frost after April 15 so always be ready to cover your asters 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.