One of the best tools that you have as gardeners to help us estimate your gardening schedule is the 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.

One way of figuring out when it's possible to plant lithospermum is to refer to the USDA zone info for Harrisburg.

Planting Calendar for Lithospermum

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

Lithospermum are not cold tolerant which tells us that you must wait until it warms up after the last frost when the weather gets warmer before you can plant them.

The earliest that you can plant lithospermum in Harrisburg 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 grow to maturity. If you are starting your lithospermum indoors then you might be able to get away with starting them a couple of weeks earlier.

Last Frost Date

In Harrisburg the average date of last frost happens on April 15. You can expect an average low temperature of 5°F in the coldest months of winter.

Since the USDA zone info for Harrisburg may not be accurate from year to year the actual date of last frost will vary from year to year. Since half of the time in Harrisburg last frost occurs after April 15 be ready to protect your lithospermum if you have one of those late frosts.

USDA Zone Info for Harrisburg

Here is the info for USDA Zone 7b.

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

Plants to Grow in Harrisburg

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