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.

A common way of getting a good idea when to plant hollyhocks is to consult the USDA zone info for Caribou.

Planting Calendar for Hollyhocks

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

Hollyhocks are one of those plants that can tolerate a little bit of cold weather which means that you can plant them a little bit earlier than plants that are more sensitive to the cold.

The earliest that you can plant hollyhocks in Caribou is March. However, you really should wait until April if you don't want to take any chances.

The last month that you can plant hollyhocks and expect a good harvest is probably August. If you wait any later than that and your hollyhocks may not have a chance to grow to maturity. If you are starting your hollyhocks indoors then you might be able to get away with starting them a few weeks earlier.

Last Frost Date

In Caribou the average date of last frost happens on May 15. It might get as low as -30°F during the coldest months of winter.

Keep in mind that USDA zone info for Caribou is not always accurate and the actual date of last frost changes from year to year. Since half of the time in Caribou it frosts late in the year after May 15 be ready to cover your hollyhocks in the event of one of those late frosts.

USDA Zone Info for Caribou

Here is the info for USDA Zone 4a.

Average Date of Last Frost (spring)	May 15
Average Date of First Frost (fall)	September 15
Lowest Expected Low	-30°F
Highest Expected Low	-25°F

This means that on a really cold year, the coldest it will get is -30°F. On most years you should be prepared to experience lows near -25°F.

Plants to Grow in Caribou

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