One of the best tools that you have as gardeners to help us figure out 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.

A common way of determining when to plant tropical hibiscus is to look at the USDA zone info for Helena.

Planting Calendar for Tropical Hibiscus

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

Tropical Hibiscus do not do well in cold weather which means that you must wait until it warms up after the last frost when the weather gets warmer before you can plant them.

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

The last month that you can plant tropical hibiscus and expect a good harvest is probably August. Any later than that and your tropical hibiscus may not have a chance to grow to maturity. Starting your tropical hibiscus indoors is a great way to get them started a little bit earlier.

Last Frost Date

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

Remember that the actual date of last frost is not always accurate because it is based on the USDA zone info for Helena and it will vary from year to year. Since half of the time in Helena there is a last frost after May 15 be ready to protect your tropical hibiscus 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.