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 estimate when to plant trachelium by looking at the USDA zone info for Boulder.

Planting Calendar for Trachelium

Frost tolerance for trachelium:	Not tolerant of frost.
When to plant:	After all chance of frost has passed.

Trachelium are not cold tolerant which tells us that you must wait until it warms up after all chance of frost has passed before you can plant them.

The earliest that you can plant trachelium in Boulder 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 trachelium and expect a good harvest is probably August. If you wait any later than that and your trachelium may not have a chance to really do well. You can get started a few weeks earlier by starting your trachelium indoors.

Last Frost Date

On average all chance of frost has passed is on April 15 in Boulder. You can expect an average low temperature of -15°F in the coldest months of winter.

Keep in mind that USDA zone info for Boulder is an average and the actual date of last frost changes from year to year. Since half of the time in Boulder it frosts late in the year after April 15 be ready to protect your trachelium in the event of one of those late frosts.

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.