One of the best tools that you have as gardeners to help us determine your gardening schedule is the USDA zone info. The zone info helps tell us things like average date of last frost and lowest expected temperature for your area.

You should be able to determine when it's a good idea to plant hardy asters by checking out the USDA zone info for Duluth.

Planting Calendar for Hardy Asters

Frost tolerance for hardy asters:	Tolerant of a very small amount of frost.
When to plant:	Up to 3 weeks before last frost.

Since hardy asters are barely cold tolerant you can plant them a bit earlier in the year than plants that are more sensitive to the cold.

The earliest that you can plant hardy asters in Duluth is April. However, you really should wait until May if you don't want to take any chances.

The last month that you can plant hardy asters and expect a good harvest is probably August. If you wait any later than that and your hardy asters may not have a chance to grow to maturity. You can get started a couple of weeks earlier by starting your hardy asters indoors.

Last Frost Date

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

Keep in mind that the actual date of last frost is not always accurate 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 cover your hardy asters in the event of a surprise 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.