One of the best tools that you have as gardeners to help us figure out 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.

In Boulder you can estimate when to plant echinacea by referring to the USDA zone info.

Planting Calendar for Echinacea

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

Echinacea do well in very little cold which means that you can plant them slightly earlier in the year than other plants that might not handle the cold.

The earliest that you can plant echinacea in Boulder 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 echinacea and expect a good harvest is probably August. You probably don't want to wait any later than that or else your echinacea may not have a chance to grow to maturity. Starting your echinacea indoors is a great way to get them started a couple of weeks earlier.

Last Frost Date

On average the last frost has passed is on April 15 in Boulder. It might get as low as -15°F during the coldest months of winter.

Since the USDA zone info for Boulder is not always accurate the actual date of last frost changes from year to year. Half of the time in Boulder you get surprised by a frost after April 15 so always be ready to protect your echinacea if you have a surprise late frost.

USDA Zone Info for Boulder

Here is the info for USDA Zone 5b.

Average Date of Last Frost (spring)	April 15
Average Date of First Frost (fall)	October 15
Lowest Expected Low	-15°F
Highest Expected Low	-10°F

This means that on a really cold year, the coldest it will get is -15°F. On most years you should be prepared to experience lows near -10°F.

Plants to Grow in Boulder

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