The USDA Zone info is a great tool for gardeners to help us estimate 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.

A common way of making a decision about when you can plant tall phlox is to examine the USDA zone info for Zone 4b.

Planting Calendar for Tall Phlox

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

Tall Phlox do ok in mild cold which tells us that you can plant them just a bit earlier in the year than more sensitive plants.

The earliest that you can plant tall phlox in Zone 4b 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 tall phlox and expect a good harvest is probably August. You probably don't want to wait any later than that or else your tall phlox may not have a chance to fully mature. You can get started a few weeks earlier by starting your tall phlox indoors.

Last Frost Date

The average date of last frost is May 15 in Zone 4b. In the coldest months of winter you can expect an average low temperature of -25°F.

It's important to remember that the actual date of last frost may not be accurate from year to year because it is based on the USDA zone info for Zone 4b and it is different every year. Half of the time in Zone 4b there is a last frost after May 15 so be sure to be ready to protect your tall phlox in the event of a surprise late frost.

USDA Zone Info for Zone 4b

Here is the info for USDA Zone 4b.

Average Date of Last Frost (spring)	May 15
Average Date of First Frost (fall)	September 15
Lowest Expected Low	-25°F
Highest Expected Low	-20°F

This means that on a really cold year, the coldest it will get is -25°F. On most years you should be prepared to experience lows near -20°F.

Plants to Grow in Zone 4b

You may be interested in your other planting guides for Zone 4b.