Before planting it is a good idea to find your USDA Zone info to estimate your garden schedule. The zone info helps tell us things like average date of last frost and lowest expected temperature for your area.

In Portsmouth you can estimate when it's possible 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.

Catharanthus require warm weather which tells us that you have to wait until it warms up after all chance of frost has passed before you can plant them.

The earliest that you can plant catharanthus in Portsmouth 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 catharanthus and expect a good harvest is probably August. Any later than that and your catharanthus may not have a chance to fully mature. Starting your catharanthus indoors is a great way to get them started a few weeks earlier.

Last Frost Date

On average the last frost has passed is on April 15 in Portsmouth. It might get as low as -5°F during the coldest months of winter.

Since the USDA zone info for Portsmouth is just an average the actual date of last frost can change quite a bit from year to year. Since half of the time in Portsmouth it frosts late in the year after April 15 be ready to cover your catharanthus in the event of a late frost.

USDA Zone Info for Portsmouth

Here is the info for USDA Zone 6b.

Average Date of Last Frost (spring)	April 15
Average Date of First Frost (fall)	October 15
Lowest Expected Low	-5°F
Highest Expected Low	0°F

This means that on a really cold year, the coldest it will get is -5°F. On most years you should be prepared to experience lows near 0°F.

Plants to Grow in Portsmouth

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