One of the first steps you take when you are figuring out your gardening schedule is find your USDA Zone info. The zone info helps tell us things like average date of last frost and lowest expected temperature for your area.

The USDA zone info for Allentown can be read to determine when it's a good idea to plant penstemon.

Planting Calendar for Penstemon

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

Penstemon are moderately cold tolerant which tells us that you can get them planted earlier than plants that are more sensitive to the cold.

The earliest that you can plant penstemon in Allentown 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. If you wait any later than that and your penstemon may not have a chance to grow to maturity. You can get started a little bit earlier by starting your penstemon indoors.

Last Frost Date

The average date of last frost is April 15 in Allentown. You should expect an average low temperature of -5°F in the coldest months of winter.

Keep in mind that the actual date of last frost is an average because it is based on the USDA zone info for Allentown and it changes from year to year. Half of the time in Allentown there is a last frost after April 15 so make sure that you are ready to protect your penstemon if you have a late frost.

USDA Zone Info for Allentown

Here is the info for USDA Zone 6b.

Average Date of Last Frost (spring)	April 15
Average Date of First Frost (fall)	October 15
Lowest Expected Low	-5°F
Highest Expected Low	0°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 0°F.

Plants to Grow in Allentown

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