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.

You can determine when it's a good idea to plant calendula in Ottumwa by using the USDA zone info.

Planting Calendar for Calendula

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

Calendula do well in moderate cold which tells us that you can get them planted earlier than more sensitive plants.

The earliest that you can plant calendula in Ottumwa 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 fully mature. You can get started a couple of weeks earlier by starting your calendula indoors.

Last Frost Date

In Ottumwa the average date of last frost happens on April 15. In the coldest months of winter you can expect an average low temperature of -15°F.

Remember that USDA zone info for Ottumwa is just an average and the actual date of last frost can change quite a bit from year to year. Half of the time in Ottumwa you get surprised by a frost after April 15 so just be sure to be ready to cover your calendula in the event of a surprise late frost.

USDA Zone Info for Ottumwa

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 Ottumwa

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