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.

You can determine when it's a good idea to plant lithospermum in Helena by referring to the USDA zone info.

Planting Calendar for Lithospermum

Frost tolerance for lithospermum:	Not tolerant of frost.
When to plant:	After the last frost when the weather gets warmer.

You really shouldn't plant lithospermum until after the last frost because they do not do well in cold weather.

The earliest that you can plant lithospermum in Helena 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 fully mature. You can get started a little bit earlier by starting your lithospermum indoors.

Last Frost Date

The average date of last frost is March 15 in Helena. In the coldest months of winter you should expect an average low temperature of 10°F.

Remember that the actual date of last frost is just an average because it is based on the USDA zone info for Helena and it is different every year. Since half of the time in Helena you get surprised by a frost after March 15 be ready to cover your lithospermum if you have a surprise late frost.

USDA Zone Info for Helena

Here is the info for USDA Zone 8a.

Average Date of Last Frost (spring)	March 15
Average Date of First Frost (fall)	November 15
Lowest Expected Low	10°F
Highest Expected Low	15°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 15°F.

Plants to Grow in Helena

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