Before planting it is a good idea to find your USDA Zone info to estimate your garden schedule. 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 determine when to plant zinnia by reviewing the USDA zone info for Granite City.

Planting Calendar for Zinnia

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

Zinnia do not do well in cold weather which tells us that you really should wait until it warms up after all chance of frost has passed before you can plant them.

The earliest that you can plant zinnia in Granite City 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. If you wait any later than that and your zinnia may not have a chance to fully mature. If you are starting your zinnia indoors then you might be able to get away with starting them a little bit earlier.

Last Frost Date

In Granite City the average date of last frost happens on April 15. You can expect an average low temperature of -5°F in the coldest months of winter.

It's important to remember that USDA zone info for Granite City is just an average and the actual date of last frost changes from year to year. Half of the time in Granite City it frosts late in the year after April 15 so make sure that you are prepared to cover your zinnia if you have a surprise late frost.

USDA Zone Info for Granite City

Here is the info for USDA Zone 6b.

Average Date of Last Frost (spring)	April 15
Average Date of First Frost (fall)	October 15
Lowest Expected Low	-5°F
Highest Expected Low	0°F

This means that on a really cold year, the coldest it will get is -5°F. On most years you should be prepared to experience lows near 0°F.

Plants to Grow in Granite City

You may be interested in your other planting guides for Granite City.