The USDA Zone info is a great tool for gardeners to help us estimate your gardening schedule. The zone info helps tell us things like average date of last frost and lowest expected temperature for your area.

The first opportunity to plant canna in Helena should be determined by looking at the USDA zone info.

Planting Calendar for Canna

Frost tolerance for canna:	Not tolerant of frost.
When to plant:	After the last frost when the weather gets warmer.

Since canna do not do well in cold weather it is necessary to wait until after the last frost before you can plant them.

The earliest that you can plant canna in Helena is May. However, you really should wait until June if you don't want to take any chances.

The last month that you can plant canna and expect a good harvest is probably August. Any later than that and your canna may not have a chance to really do well. You can get started a little bit earlier by starting your canna indoors.

Last Frost Date

The average date of last frost is May 15 in Helena. It might get as low as -25°F during the coldest months of winter.

Remember that the actual date of last frost is just an average because it is based on the USDA zone info for Helena and it changes from year to year. Half of the time in Helena you get a frost after May 15 so make sure that you are ready to cover your canna in the event of 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.