One of the best tools that you have as gardeners to help us determine your gardening schedule is the USDA zone info. The most important data that the zone info tells us is average last frost and the lowest expected temperature for your area.

You should be able to estimate when to plant fennel by referring to the USDA zone info for Marshalltown.

Planting Calendar for Fennel

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

Fennel do well in cold which tells us that you can plant them a quite a bit earlier than other plants that might not handle the cold.

The earliest that you can plant fennel in Marshalltown 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. Any later than that and your fennel may not have a chance to grow to maturity. You can get started a few weeks earlier by starting your fennel indoors.

Last Frost Date

The average date of last frost is April 15 in Marshalltown. It might get as low as -20°F during the coldest months of winter.

It's important to remember that the actual date of last frost is just an average because it is based on the USDA zone info for Marshalltown and it changes from year to year. Half of the time in Marshalltown you get surprised by a frost after April 15 so be sure to be ready to protect your fennel in the event of one of those late frosts.

USDA Zone Info for Marshalltown

Here is the info for USDA Zone 5a.

Average Date of Last Frost (spring)	April 15
Average Date of First Frost (fall)	October 15
Lowest Expected Low	-20°F
Highest Expected Low	-15°F

This means that on a really cold year, the coldest it will get is -20°F. On most years you should be prepared to experience lows near -15°F.

Plants to Grow in Marshalltown

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