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.

In Billings you can determine when it's the best time to plant catharanthus by checking out the USDA zone info.

Planting Calendar for Catharanthus

Frost tolerance for catharanthus:	Not tolerant of frost.
When to plant:	After the last frost.

It's not a good idea to plant catharanthus until after the last frost when the weather gets warmer because they do not do well in cold weather.

The earliest that you can plant catharanthus in Billings 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 catharanthus and expect a good harvest is probably August. You probably don't want to wait any later than that or else your catharanthus may not have a chance to fully mature. You can get started a little bit earlier by starting your catharanthus indoors.

Last Frost Date

On average the last frost is on May 15 in Billings. It might get as low as -25°F during the coldest months of winter.

Remember that USDA zone info for Billings is just an average and the actual date of last frost will vary from year to year. Half of the time in Billings there is a last frost after May 15 so make sure that you are ready to cover your catharanthus if you have a late frost.

USDA Zone Info for Billings

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 Billings

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