The USDA Zone info is a great tool for gardeners to help us figure out your gardening schedule. The most important data that the zone info tells us is average last frost and the lowest expected temperature for your area.

By checking out the USDA zone info for Harrisburg you should be able to estimate when it's the best time to plant tall phlox.

Planting Calendar for Tall Phlox

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

Since tall phlox are moderately cold tolerant you can plant them just a bit earlier in the year than other plants that might not handle the cold.

The earliest that you can plant tall phlox in Harrisburg 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 tall phlox and expect a good harvest is probably September. Any later than that and your tall phlox may not have a chance to really do well. You can get started a few weeks earlier by starting your tall phlox indoors.

Last Frost Date

On average the last frost is on April 15 in Harrisburg. In the coldest months of winter you should expect an average low temperature of 0°F.

Since the USDA zone info for Harrisburg is just an average the actual date of last frost can change quite a bit from year to year. Since half of the time in Harrisburg you get surprised by a frost after April 15 be ready to cover your tall phlox if you have a late frost.

USDA Zone Info for Harrisburg

Here is the info for USDA Zone 7a.

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

This means that on a really cold year, the coldest it will get is 0°F. On most years you should be prepared to experience lows near 5°F.

Plants to Grow in Harrisburg

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