One of the first steps you take when you are estimating your gardening schedule is find your USDA Zone info. The zone info helps tell us things like average date of last frost and lowest expected temperature for your area.

The USDA zone info for Willowbrook should be reffered to in order to figure out when it's a good idea to plant common hollyhock.

Planting Calendar for Common hollyhock

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

Since common hollyhock do well in moderate cold you can plant them a bit earlier in the year than plants that are more sensitive to the cold.

The earliest that you can plant common hollyhock in Willowbrook 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. If you wait any later than that and your common hollyhock may not have a chance to really do well. 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

In Willowbrook the average date of last frost happens on April 15. It might get as low as -15°F during the coldest months of winter.

Since the USDA zone info for Willowbrook is just an average the actual date of last frost can change quite a bit from year to year. Half of the time in Willowbrook it frosts late in the year after April 15 so make sure that you are prepared to protect your common hollyhock in the event of a late frost.

USDA Zone Info for Willowbrook

Here is the info for USDA Zone 5b.

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

This means that on a really cold year, the coldest it will get is -15°F. On most years you should be prepared to experience lows near -10°F.

Plants to Grow in Willowbrook

You may be interested in your other planting guides for Willowbrook.