One of the best tools that you have as gardeners to help us determine your gardening schedule is the USDA zone info. 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 estimating when it's possible to plant phlox is to check out the USDA zone info for Duluth.

Planting Calendar for Phlox

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

You can plant phlox a little bit earlier in the year because they are moderately cold tolerant.

The earliest that you can plant phlox in Duluth 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 phlox and expect a good harvest is probably August. You probably don't want to wait any later than that or else your phlox may not have a chance to grow to maturity. If you are starting your phlox indoors then you might be able to get away with starting them a few weeks earlier.

Last Frost Date

In Duluth the average date of last frost happens on May 15. You should expect an average low temperature of -30°F in the coldest months of winter.

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 Duluth and it can change quite a bit from year to year. Since half of the time in Duluth you get surprised by a frost after May 15 be ready to protect your phlox in the event of a late frost.

USDA Zone Info for Duluth

Here is the info for USDA Zone 4a.

Average Date of Last Frost (spring)	May 15
Average Date of First Frost (fall)	September 15
Lowest Expected Low	-30°F
Highest Expected Low	-25°F

This means that on a really cold year, the coldest it will get is -30°F. On most years you should be prepared to experience lows near -25°F.

Plants to Grow in Duluth

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