Before planting it is a good idea to find your USDA Zone info to figure out your garden schedule. The most important data that the zone info tells us is average last frost and the lowest expected temperature for your area.

A way of estimating when to plant common hollyhock is to check out the USDA zone info for River Forest.

Planting Calendar for Common hollyhock

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

Common hollyhock do well in moderate cold which tells us that you can plant them earlier than other frost tender plants.

The earliest that you can plant common hollyhock in River Forest 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 common hollyhock and expect a good harvest is probably September. Any later than that and your common hollyhock may not have a chance to fully mature. If you are starting your common hollyhock indoors then you might be able to get away with starting them a few weeks earlier.

Last Frost Date

The average date of last frost is April 15 in River Forest. In the coldest months of winter you can expect an average low temperature of -10°F.

Keep in mind that the actual date of last frost is not always accurate because it is based on the USDA zone info for River Forest and it can change quite a bit from year to year. Since half of the time in River Forest it frosts late in the year after April 15 be ready to cover your common hollyhock in the event of a surprise late frost.

USDA Zone Info for River Forest

Here is the info for USDA Zone 6a.

Average Date of Last Frost (spring)	April 15
Average Date of First Frost (fall)	October 15
Lowest Expected Low	-10°F
Highest Expected Low	-5°F

This means that on a really cold year, the coldest it will get is -10°F. On most years you should be prepared to experience lows near -5°F.

Plants to Grow in River Forest

You may be interested in your other planting guides for River Forest.