One of the best tools that you have as gardeners to help us figure out your gardening schedule is the USDA zone info. The zone info helps tell us things like average date of last frost and lowest expected temperature for your area.

A way of getting a good idea when to plant pentas is to look at the USDA zone info for River Falls.

Planting Calendar for Pentas

Frost tolerance for pentas:	Not tolerant of frost.
When to plant:	After all chance of frost has passed.

It's not a good idea to plant pentas until after the last frost has passed because they require warm weather.

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

Last Frost Date

In River Falls the average date of last frost happens on May 15. You can expect an average low temperature of -25°F in the coldest months of winter.

Since the USDA zone info for River Falls is just an average the actual date of last frost is different every year. Half of the time in River Falls it frosts late in the year after May 15 so be sure to be ready to cover your pentas if you have a surprise late frost.

USDA Zone Info for River Falls

Here is the info for USDA Zone 4b.

Average Date of Last Frost (spring)	May 15
Average Date of First Frost (fall)	September 15
Lowest Expected Low	-25°F
Highest Expected Low	-20°F

This means that on a really cold year, the coldest it will get is -25°F. On most years you should be prepared to experience lows near -20°F.

Plants to Grow in River Falls

You may be interested in your other planting guides for River Falls.