The USDA Zone info is a great tool for gardeners to help us figure out your gardening schedule. 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 Helena can be looked at to determine when it's possible to plant armeria.

Planting Calendar for Armeria

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

Since armeria are one of those plants that can tolerate quite a bit of cold weather you can plant them quite a bit earlier in the year than other frost tender plants.

The earliest that you can plant armeria in Helena 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 armeria and expect a good harvest is probably September. Any later than that and your armeria may not have a chance to grow to maturity. If you are starting your armeria indoors then you might be able to get away with starting them a few weeks earlier.

Last Frost Date

In Helena the average date of last frost happens on March 15. In the coldest months of winter you can expect an average low temperature of 10°F.

Remember that the actual date of last frost is an average because it is based on the USDA zone info for Helena and it changes from year to year. Since half of the time in Helena you get surprised by a frost after March 15 be ready to cover your armeria in the event of one of those late frosts.

USDA Zone Info for Helena

Here is the info for USDA Zone 8a.

Average Date of Last Frost (spring)	March 15
Average Date of First Frost (fall)	November 15
Lowest Expected Low	10°F
Highest Expected Low	15°F

This means that on a really cold year, the coldest it will get is 10°F. On most years you should be prepared to experience lows near 15°F.

Plants to Grow in Helena

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