One of the first steps you take when you are making a decision about your gardening schedule is find your USDA Zone info. The zone info helps tell us things like average date of last frost and lowest expected temperature for your area.

In Ottumwa you can estimate when you can plant nierembergia by using the USDA zone info.

Planting Calendar for Nierembergia

Frost tolerance for nierembergia:	Not tolerant of frost.
When to plant:	After the last frost when the weather gets warmer.

It's a bad idea to plant nierembergia until after the last frost has passed because they require warm weather.

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

The last month that you can plant nierembergia and expect a good harvest is probably August. If you wait any later than that and your nierembergia may not have a chance to fully mature. If you are starting your nierembergia indoors then you might be able to get away with starting them a little bit earlier.

Last Frost Date

In Ottumwa the average date of last frost happens on April 15. It might get as low as -15°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 Ottumwa and it can change quite a bit from year to year. Since half of the time in Ottumwa you get a frost after April 15 be ready to cover your nierembergia in the event of a 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.