Before planting it is a good idea to find your USDA Zone info to figure out your garden schedule. The zone info helps tell us things like average date of last frost and lowest expected temperature for your area.

One way of getting a good idea when it's possible to plant yarrow is to check out the USDA zone info for Caribou.

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 plant them a quite a bit earlier than other frost tender plants.

The earliest that you can plant yarrow in Caribou 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 fully mature. Starting your yarrow indoors is a great way to get them started a couple of weeks earlier.

Last Frost Date

On average the last frost is on May 15 in Caribou. You should expect an average low temperature of -30°F in the coldest months of winter.

Since the USDA zone info for Caribou may not be accurate from year to year the actual date of last frost is different every year. Since half of the time in Caribou it frosts late in the year after May 15 be ready to cover your yarrow in the event of a late frost.

USDA Zone Info for Caribou

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 Caribou

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