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

One way of determining when it's the best time to plant fennel is to refer to the USDA zone info for Naperville.

Planting Calendar for Fennel

Frost tolerance for fennel:	Very tolerant of frost.
When to plant:	Up to 7 weeks before last frost.

Fennel tend to make it in a bit of cold which means that you can plant them quite a bit earlier in the year than more sensitive plants.

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

Last Frost Date

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

Since the USDA zone info for Naperville is an average the actual date of last frost can change quite a bit from year to year. Half of the time in Naperville last frost occurs after April 15 so just be sure to be ready to protect your fennel if you have one of those late frosts.

USDA Zone Info for Naperville

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 Naperville

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