One of the best tools that you have as gardeners to help us estimate your gardening schedule is the 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 looked at to determine when to plant calendula.

Planting Calendar for Calendula

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

Calendula are one of those plants that can tolerate a little bit of cold weather which means that you can start planting them earlier than more sensitive plants.

The earliest that you can plant calendula 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 calendula and expect a good harvest is probably September. Any later than that and your calendula may not have a chance to grow to maturity. If you are starting your calendula indoors then you might be able to get away with starting them a little bit earlier.

Last Frost Date

On average the last frost is on April 15 in Willowbrook. It might get as low as -15°F during the coldest months of winter.

Just be sure to remember that the actual date of last frost is an average because it is based on the USDA zone info for Willowbrook and it will vary from year to year. Half of the time in Willowbrook you get a frost after April 15 so just be sure to be ready to cover your calendula 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.