One of the first steps you take when you are getting a good idea your gardening schedule is find your 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.

By referring to the USDA zone info for Portsmouth you should be able to determine when it's possible to plant nierembergia.

Planting Calendar for Nierembergia

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

Nierembergia are not cold tolerant which tells us that you need to wait until it warms up after all chance of frost has passed before you can plant them.

The earliest that you can plant nierembergia 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 nierembergia and expect a good harvest is probably August. If you wait any later than that and your nierembergia may not have a chance to really do well. You can get started a couple of weeks earlier by starting your nierembergia indoors.

Last Frost Date

On average the last frost has passed is on April 15 in Portsmouth. You can expect an average low temperature of -5°F in the coldest months of winter.

Keep in mind that USDA zone info for Portsmouth is an average and the actual date of last frost can change quite a bit from year to year. Half of the time in Portsmouth there is a last frost after April 15 so be sure to be ready to cover your nierembergia in the event of a surprise 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.