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 getting a good idea when to plant phlox is to check out the USDA zone info for Helena.

Planting Calendar for Phlox

Frost tolerance for phlox:	Tolerant of some frost.
When to plant:	Up to 5 weeks before last frost.

You can plant phlox a little bit earlier in the year because they do well in moderate cold.

The earliest that you can plant phlox 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 phlox and expect a good harvest is probably September. If you wait any later than that and your phlox may not have a chance to grow to maturity. You can get started a little bit earlier by starting your phlox indoors.

Last Frost Date

On average all chance of frost has passed is on March 15 in Helena. It might get as low as 10°F during the coldest months of winter.

Since the USDA zone info for Helena may not be accurate from year to year the actual date of last frost can change quite a bit from year to year. Half of the time in Helena last frost occurs after March 15 so make sure that you are ready to cover your phlox in the event of a surprise late frost.

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.