One of the best tools that you have as gardeners to help us determine your gardening schedule is the USDA zone info. The most important data that the zone info tells us is average last frost and the lowest expected temperature for your area.

The first opportunity to plant sweet corn in Helena can be determined by reviewing the USDA zone info.

Planting Calendar for Sweet corn

Frost tolerance for sweet corn:	Tolerant of a very small amount of frost.
When to plant:	Up to 3 weeks before last frost.

Since sweet corn are barely cold tolerant you can plant them just a tiny bit earlier in the year than other plants that might not handle the cold.

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

The last month that you can plant sweet corn and expect a good harvest is probably August. You probably don't want to wait any later than that or else your sweet corn may not have a chance to really do well. If you are starting your sweet corn indoors then you might be able to get away with starting them a little bit earlier.

Last Frost Date

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

It's important to remember that USDA zone info for Helena may not be accurate from year to year and the actual date of last frost will vary from year to year. Since half of the time in Helena last frost occurs after May 15 be ready to cover your sweet corn in the event of one of those late frosts.

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.