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

By referring to the USDA zone info for Superior you should be able to estimate when it's possible to plant yarrow.

Planting Calendar for Yarrow

Frost tolerance for yarrow:	Very tolerant of frost.
When to plant:	Up to 7 weeks before last frost.

Yarrow are very cold tolerant which means that you can start planting them much earlier than more sensitive plants.

The earliest that you can plant yarrow in Superior 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 yarrow and expect a good harvest is probably August. Any later than that and your yarrow may not have a chance to grow to maturity. Starting your yarrow indoors is a great way to get them started a little bit earlier.

Last Frost Date

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

Keep in mind that USDA zone info for Superior is just an average and the actual date of last frost can change quite a bit from year to year. Since half of the time in Superior you get a frost after May 15 be ready to protect your yarrow if you have a surprise late frost.

USDA Zone Info for Superior

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 Superior

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