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.

You can estimate when you can plant alternanthera in Helena by reviewing the USDA zone info.

Planting Calendar for Alternanthera

Frost tolerance for alternanthera:	Not tolerant of frost.
When to plant:	After all chance of frost has passed.

You really shouldn't plant alternanthera until after the last frost when the weather gets warmer because they are not cold tolerant.

The earliest that you can plant alternanthera 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 alternanthera and expect a good harvest is probably August. Any later than that and your alternanthera may not have a chance to grow to maturity. Starting your alternanthera indoors is a great way to get them started a couple of weeks earlier.

Last Frost Date

In Helena the average date of last frost happens on March 15. In the coldest months of winter you can expect an average low temperature of 10°F.

Remember that USDA zone info for Helena is not always accurate and the actual date of last frost is different every year. Half of the time in Helena you get a frost after March 15 so always be ready to protect your alternanthera if you have a late frost.

USDA Zone Info for Helena

Here is the info for USDA Zone 8a.

Average Date of Last Frost (spring)	March 15
Average Date of First Frost (fall)	November 15
Lowest Expected Low	10°F
Highest Expected Low	15°F

This means that on a really cold year, the coldest it will get is 10°F. On most years you should be prepared to experience lows near 15°F.

Plants to Grow in Helena

You may be interested in your other planting guides for Helena.