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 way of figuring out when it's the best time to plant achillea is to use the USDA zone info for Green River.

Planting Calendar for Achillea

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

Achillea do well in cold which means that you can start planting them much earlier than plants that are more sensitive to the cold.

The earliest that you can plant achillea in Green River 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 achillea and expect a good harvest is probably August. Any later than that and your achillea may not have a chance to grow to maturity. You can get started a couple of weeks earlier by starting your achillea indoors.

Last Frost Date

The average date of last frost is May 15 in Green River. You should expect an average low temperature of -25°F in the coldest months of winter.

Keep in mind that the actual date of last frost is an average because it is based on the USDA zone info for Green River and it can change quite a bit from year to year. Half of the time in Green River there is a last frost after May 15 so be sure to be ready to cover your achillea in the event of one of those late frosts.

USDA Zone Info for Green River

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 Green River

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