The USDA Zone info is a great tool for gardeners to help us figure out your gardening schedule. The zone info helps tell us things like average date of last frost and lowest expected temperature for your area.

One way of getting a good idea when it's possible to plant hollyhocks is to look at the USDA zone info for River Grove.

Planting Calendar for Hollyhocks

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

Hollyhocks tend to make it in a little bit of cold which tells us that you can plant them just a bit earlier in the year than plants that are more sensitive to the cold.

The earliest that you can plant hollyhocks in River Grove 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 hollyhocks and expect a good harvest is probably September. If you wait any later than that and your hollyhocks may not have a chance to grow to maturity. Starting your hollyhocks indoors is a great way to get them started a few weeks earlier.

Last Frost Date

In River Grove the average date of last frost happens on April 15. In the coldest months of winter you should expect an average low temperature of -15°F.

Always keep in mind that USDA zone info for River Grove is an average and the actual date of last frost can change quite a bit from year to year. Half of the time in River Grove it frosts late in the year after April 15 so just be sure to be ready to protect your hollyhocks if you have a surprise late frost.

USDA Zone Info for River Grove

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 River Grove

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