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 it's a good idea to plant common hollyhock by referring to the USDA zone info for Hillsboro.

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 are moderately cold tolerant which means that you can plant them a little bit earlier than more sensitive plants.

The earliest that you can plant common hollyhock in Hillsboro 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 fully mature. Starting your common hollyhock indoors is a great way to get them started a few weeks earlier.

Last Frost Date

On average the last frost is on April 15 in Hillsboro. You should expect an average low temperature of -10°F in the coldest months of winter.

It's important to remember that USDA zone info for Hillsboro is an average and the actual date of last frost is different every year. Since half of the time in Hillsboro you get surprised by a frost after April 15 be ready to protect your common hollyhock in the event of one of those late frosts.

USDA Zone Info for Hillsboro

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 Hillsboro

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