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 it's the best time to plant cosmos by referring to the USDA zone info for Omaha.

Planting Calendar for Cosmos

Frost tolerance for cosmos:	Tolerant of a very small amount of frost.
When to plant:	Up to 3 weeks before last frost.

You can plant cosmos slightly earlier in the year because they are barely cold tolerant.

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

The last month that you can plant cosmos and expect a good harvest is probably August. You probably don't want to wait any later than that or else your cosmos may not have a chance to grow to maturity. You can get started a couple of weeks earlier by starting your cosmos indoors.

Last Frost Date

In Omaha the average date of last frost happens on April 15. 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 not always accurate because it is based on the USDA zone info for Omaha and it changes from year to year. Half of the time in Omaha you get surprised by a frost after April 15 so always be ready to protect your cosmos in the event of a late frost.

USDA Zone Info for Omaha

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 Omaha

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