One of the first steps you take when you are getting a good idea 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.

The first chance to plant sunflowers in Waterloo should be determined by referring to the USDA zone info.

Planting Calendar for Sunflowers

Frost tolerance for sunflowers:	Not tolerant of frost.
When to plant:	After the last frost.

Since sunflowers are not cold tolerant you really should wait until after the last frost before you can plant them.

The earliest that you can plant sunflowers in Waterloo 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 sunflowers and expect a good harvest is probably August. Any later than that and your sunflowers may not have a chance to fully mature. If you are starting your sunflowers indoors then you might be able to get away with starting them a few weeks earlier.

Last Frost Date

On average the last frost has passed is on April 15 in Waterloo. In the coldest months of winter you should expect an average low temperature of -20°F.

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 Waterloo and it will vary from year to year. Since half of the time in Waterloo last frost occurs after April 15 be ready to protect your sunflowers in the event of one of those late frosts.

USDA Zone Info for Waterloo

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 Waterloo

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