Before planting it is a good idea to find your USDA Zone info to determine your garden schedule. The most important data that the zone info tells us is average last frost and the lowest expected temperature for your area.

The first chance to plant jerusalem artichokes in Helena should be figured out by checking out the USDA zone info.

Planting Calendar for Jerusalem artichokes

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

Since jerusalem artichokes do well in moderate cold you can plant them a little bit earlier in the year than other frost tender plants.

The earliest that you can plant jerusalem artichokes 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 jerusalem artichokes and expect a good harvest is probably August. Any later than that and your jerusalem artichokes may not have a chance to fully mature. You can get started a couple of weeks earlier by starting your jerusalem artichokes indoors.

Last Frost Date

On average the last frost has passed is on 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 not always accurate the actual date of last frost can change quite a bit from year to year. Half of the time in Helena you get surprised by a frost after May 15 so make sure that you are ready to protect your jerusalem artichokes if you have a surprise 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.