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 should be able to estimate when it's possible to plant penstemon by referring to the USDA zone info for South Portland.

Planting Calendar for Penstemon

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

Since penstemon are moderately cold tolerant you can plant them a bit earlier in the year than more sensitive plants.

The earliest that you can plant penstemon in South Portland is February. However, you really should wait until March if you don't want to take any chances.

The last month that you can plant penstemon and expect a good harvest is probably September. Any later than that and your penstemon may not have a chance to grow to maturity. If you are starting your penstemon indoors then you might be able to get away with starting them a couple of weeks earlier.

Last Frost Date

On average the last frost is on April 15 in South Portland. In the coldest months of winter you should expect an average low temperature of -15°F.

It's important to remember that the actual date of last frost is just an average because it is based on the USDA zone info for South Portland and it will vary from year to year. Half of the time in South Portland you get a frost after April 15 so make sure that you are prepared to protect your penstemon if you have one of those late frosts.

USDA Zone Info for South Portland

Here is the info for USDA Zone 5b.

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

This means that on a really cold year, the coldest it will get is -15°F. On most years you should be prepared to experience lows near -10°F.

Plants to Grow in South Portland

You may be interested in your other planting guides for South Portland.