Before planting it is a good idea to find your USDA Zone info to figure out your garden schedule. The zone info helps tell us things like average date of last frost and lowest expected temperature for your area.

You can estimate when to plant erysimum in Helena by looking at the USDA zone info.

Planting Calendar for Erysimum

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

Since erysimum are one of those plants that can tolerate a little bit of cold weather you can plant them a bit earlier in the year than plants that are more sensitive to the cold.

The earliest that you can plant erysimum 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 erysimum and expect a good harvest is probably August. You probably don't want to wait any later than that or else your erysimum may not have a chance to really do well. If you are starting your erysimum 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 May 15. It might get as low as -25°F during the coldest months of winter.

It's important to remember that the actual date of last frost is not always accurate because it is based on the USDA zone info for Helena and it can change quite a bit from year to year. Half of the time in Helena it frosts late in the year after May 15 so always be ready to protect your erysimum 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.