The USDA Zone info is a great tool for gardeners to help us determine your gardening schedule. The zone info helps tell us things like average date of last frost and lowest expected temperature for your area.

A way of figuring out when it's possible to plant yarrow is to use the USDA zone info for Zone 4b.

Planting Calendar for Yarrow

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

Yarrow do well in cold which means that you can start planting them much earlier than more sensitive plants.

The earliest that you can plant yarrow in Zone 4b 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 Zone 4b the average date of last frost happens on May 15. It might get as low as -25°F during the coldest months of winter.

Since the USDA zone info for Zone 4b is just an average the actual date of last frost is different every year. Since half of the time in Zone 4b you get surprised by a frost after May 15 be ready to protect your yarrow if you have a late frost.

USDA Zone Info for Zone 4b

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 Zone 4b

You may be interested in your other planting guides for Zone 4b.