Before planting it is a good idea to find your USDA Zone info to determine 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.

By checking out the USDA zone info for Denver it's a good idea to determine when it's the best time 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.

Common hollyhock are one of those plants that can tolerate a little bit of cold weather which means that you can get them planted earlier than more sensitive plants.

The earliest that you can plant common hollyhock in Denver 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. You can get started a couple of weeks earlier by starting your common hollyhock indoors.

Last Frost Date

The average date of last frost is April 15 in Denver. It might get as low as -15°F during the coldest months of winter.

It's important to remember that USDA zone info for Denver is not always accurate and the actual date of last frost is different every year. Half of the time in Denver you get surprised by a frost after April 15 so be sure to be ready to protect your common hollyhock in the event of a late frost.

USDA Zone Info for Denver

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 Denver

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