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 earliest that you can plant trifolium in Helena can be estimated by referring to the USDA zone info.

Planting Calendar for Trifolium

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

Trifolium do ok in moderate cold which means that you can start planting them slightly earlier than more sensitive plants.

The earliest that you can plant trifolium 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 trifolium and expect a good harvest is probably August. Any later than that and your trifolium may not have a chance to fully mature. Starting your trifolium indoors is a great way to get them started a few weeks 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.

Keep in mind that the actual date of last frost is an average because it is based on the USDA zone info for Helena and it is different every 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 trifolium 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.