One of the first steps you take when you are figuring out 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.

A way of making a decision about when it's possible to plant anchusa is to consult the USDA zone info for Helena.

Planting Calendar for Anchusa

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

Anchusa do ok in pretty solid cold which tells us that you can plant them earlier in the year than other frost tender plants.

The earliest that you can plant anchusa in Helena 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 anchusa and expect a good harvest is probably August. You probably don't want to wait any later than that or else your anchusa may not have a chance to grow to maturity. Starting your anchusa indoors is a great way to get them started a couple of weeks earlier.

Last Frost Date

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

Since the USDA zone info for Helena is just an average the actual date of last frost will vary from year to year. Half of the time in Helena it frosts late in the year after May 15 so just be sure to be ready to protect your anchusa if you have a late frost.

USDA Zone Info for Helena

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 Helena

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