Before planting it is a good idea to find your USDA Zone info to estimate your garden schedule. 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 it's a good idea to determine when you can plant lithospermum.

Planting Calendar for Lithospermum

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

Lithospermum require warm weather which means that it's important to wait until it warms up after all chance of frost has passed before you can plant them.

The earliest that you can plant lithospermum 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 lithospermum and expect a good harvest is probably August. Any later than that and your lithospermum may not have a chance to really do well. You can get started a few weeks earlier by starting your lithospermum indoors.

Last Frost Date

In Portsmouth the average date of last frost happens on April 15. It might get as low as -10°F during the coldest months of winter.

Since the USDA zone info for Portsmouth is not always accurate the actual date of last frost will vary from year to year. Since half of the time in Portsmouth you get a frost after April 15 be ready to protect your lithospermum if you have a late frost.

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.