One of the best tools that you have as gardeners to help us estimate 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.

A common way of getting a good idea when it's a good idea to plant sunflowers is to consult the USDA zone info for Rhinelander.

Planting Calendar for Sunflowers

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

Sunflowers do not do well in cold weather which tells us that it is necessary to wait until it warms up after the last frost before you can plant them.

The earliest that you can plant sunflowers in Rhinelander is May. However, you really should wait until June 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. You probably don't want to wait any later than that or else your sunflowers may not have a chance to grow to maturity. 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

In Rhinelander the average date of last frost happens on May 15. It might get as low as -30°F during the coldest months of winter.

Remember that USDA zone info for Rhinelander is an average and the actual date of last frost can change quite a bit from year to year. Since half of the time in Rhinelander it frosts late in the year after May 15 be ready to protect your sunflowers in the event of a late frost.

USDA Zone Info for Rhinelander

Here is the info for USDA Zone 4a.

Average Date of Last Frost (spring)	May 15
Average Date of First Frost (fall)	September 15
Lowest Expected Low	-30°F
Highest Expected Low	-25°F

This means that on a really cold year, the coldest it will get is -30°F. On most years you should be prepared to experience lows near -25°F.

Plants to Grow in Rhinelander

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