The USDA Zone info is a great tool for gardeners to help us figure out your gardening schedule. The most important data that the zone info tells us is average last frost and the lowest expected temperature for your area.

The USDA zone info for Helena can be read to figure out when it's possible to plant sweet woodruff.

Planting Calendar for Sweet Woodruff

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

Sweet Woodruff are one of those plants that can tolerate a little bit of cold weather which tells us that you can plant them earlier than more sensitive plants.

The earliest that you can plant sweet woodruff 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 sweet woodruff and expect a good harvest is probably August. Any later than that and your sweet woodruff may not have a chance to really do well. If you are starting your sweet woodruff indoors then you might be able to get away with starting them a few weeks earlier.

Last Frost Date

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

Since the USDA zone info for Helena is an average the actual date of last frost is different every year. Since half of the time in Helena it frosts late in the year after May 15 be ready to cover your sweet woodruff 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.