Before planting it is a good idea to find your USDA Zone info to figure out 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 estimate when it's possible to plant penstemon in Zone 3b by looking at the USDA zone info.

Planting Calendar for Penstemon

Frost tolerance for penstemon:	Tolerant of some frost.
When to plant:	Up to 5 weeks before last frost.

Since penstemon do well in moderate cold you can plant them a little bit earlier in the year than other frost tender plants.

The earliest that you can plant penstemon in Zone 3b is March. However, you really should wait until April if you don't want to take any chances.

The last month that you can plant penstemon and expect a good harvest is probably August. Any later than that and your penstemon may not have a chance to really do well. Starting your penstemon indoors is a great way to get them started a little bit earlier.

Last Frost Date

On average the last frost has passed is on May 15 in Zone 3b. It might get as low as -35°F during the coldest months of winter.

It's important to remember that the actual date of last frost is not always accurate because it is based on the USDA zone info for Zone 3b and it is different every year. Half of the time in Zone 3b you get surprised by a frost after May 15 so make sure that you are ready to cover your penstemon if you have one of those late frosts.

USDA Zone Info for Zone 3b

Here is the info for USDA Zone 3b.

Average Date of Last Frost (spring)	May 15
Average Date of First Frost (fall)	September 15
Lowest Expected Low	-35°F
Highest Expected Low	-30°F

This means that on a really cold year, the coldest it will get is -35°F. On most years you should be prepared to experience lows near -30°F.

Plants to Grow in Zone 3b

You may be interested in your other planting guides for Zone 3b.