The USDA Zone info is a great tool for gardeners to help us determine your gardening schedule. The most important data that the zone info tells us is average last frost and the lowest expected temperature for your area.

One way of estimating when it's possible to plant alternanthera is to look at the USDA zone info for Portsmouth.

Planting Calendar for Alternanthera

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

Alternanthera are not cold tolerant which tells us that it's important to wait until it warms up after the last frost has passed before you can plant them.

The earliest that you can plant alternanthera 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 alternanthera and expect a good harvest is probably August. If you wait any later than that and your alternanthera may not have a chance to really do well. If you are starting your alternanthera indoors then you might be able to get away with starting them a couple of weeks earlier.

Last Frost Date

In Portsmouth the average date of last frost happens on April 15. You can expect an average low temperature of -10°F in the coldest months of winter.

Always keep in mind that the actual date of last frost is an average because it is based on the USDA zone info for Portsmouth and it will vary from year to year. Half of the time in Portsmouth you get a frost after April 15 so make sure that you are prepared to protect your alternanthera if you have one of those late frosts.

USDA Zone Info for Portsmouth

Here is the info for USDA Zone 6a.

Average Date of Last Frost (spring)	April 15
Average Date of First Frost (fall)	October 15
Lowest Expected Low	-10°F
Highest Expected Low	-5°F

This means that on a really cold year, the coldest it will get is -10°F. On most years you should be prepared to experience lows near -5°F.

Plants to Grow in Portsmouth

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