One of the first steps you take when you are getting a good idea 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 Zone 3b you can determine when to plant catharanthus by referring to the USDA zone info.

Planting Calendar for Catharanthus

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

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

The earliest that you can plant catharanthus in Zone 3b 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 grow to maturity. Starting your catharanthus indoors is a great way to get them started a little bit earlier.

Last Frost Date

The average date of last frost is May 15 in Zone 3b. It might get as low as -35°F during the coldest months of winter.

Since the USDA zone info for Zone 3b is an average the actual date of last frost will vary from year to year. Since half of the time in Zone 3b you get surprised by a frost after May 15 be ready to protect your catharanthus if you have a late frost.

USDA Zone Info for Zone 3b

Here is the info for USDA Zone 3b.

Average Date of Last Frost (spring)	May 15
Average Date of First Frost (fall)	September 15
Lowest Expected Low	-35°F
Highest Expected Low	-30°F

This means that on a really cold year, the coldest it will get is -35°F. On most years you should be prepared to experience lows near -30°F.

Plants to Grow in Zone 3b

You may be interested in your other planting guides for Zone 3b.