The USDA Zone info is a great tool for gardeners to help us estimate your gardening schedule. 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 the best time to plant pyrethrum by referring to the USDA zone info for Duluth.

Planting Calendar for Pyrethrum

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

Since pyrethrum do well in moderate cold you can plant them just a bit earlier in the year than other frost tender plants.

The earliest that you can plant pyrethrum 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 pyrethrum and expect a good harvest is probably August. If you wait any later than that and your pyrethrum may not have a chance to grow to maturity. Starting your pyrethrum indoors is a great way to get them started a little bit earlier.

Last Frost Date

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

Just be sure to remember that USDA zone info for Duluth is an average and the actual date of last frost will vary from year to year. Half of the time in Duluth there is a last frost after May 15 so make sure that you are ready to cover your pyrethrum if you have 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.