One of the first steps you take when you are figuring out your gardening schedule is find your USDA Zone info. The zone info helps tell us things like average date of last frost and lowest expected temperature for your area.

In Helena you can estimate when you can plant pennisetum by using the USDA zone info.

Planting Calendar for Pennisetum

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

Since pennisetum are one of those plants that can tolerate a tiny bit of cold weather you can plant them a bit earlier in the year than other plants that might not handle the cold.

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

Last Frost Date

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

It's important to remember 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 there is a last frost after May 15 so always be ready to protect your pennisetum in the event of a surprise 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.