One of the first steps you take when you are determining your gardening schedule is find your USDA Zone info. The zone info helps tell us things like average date of last frost and lowest expected temperature for your area.

The USDA zone info for Casper can be reffered to in order to estimate when it's possible to plant achillea.

Planting Calendar for Achillea

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

Since achillea do well in cold you can plant them much earlier in the year than more sensitive plants.

The earliest that you can plant achillea in Casper is February. However, you really should wait until March if you don't want to take any chances.

The last month that you can plant achillea and expect a good harvest is probably September. If you wait any later than that and your achillea may not have a chance to fully mature. You can get started a few weeks earlier by starting your achillea indoors.

Last Frost Date

In Casper the average date of last frost happens on April 15. It might get as low as -20°F during the coldest months of winter.

Remember that the actual date of last frost is not always accurate because it is based on the USDA zone info for Casper and it will vary from year to year. Since half of the time in Casper last frost occurs after April 15 be ready to protect your achillea if you have a late frost.

USDA Zone Info for Casper

Here is the info for USDA Zone 5a.

Average Date of Last Frost (spring)	April 15
Average Date of First Frost (fall)	October 15
Lowest Expected Low	-20°F
Highest Expected Low	-15°F

This means that on a really cold year, the coldest it will get is -20°F. On most years you should be prepared to experience lows near -15°F.

Plants to Grow in Casper

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