Before planting it is a good idea to find your USDA Zone info to estimate your garden schedule. The zone info helps tell us things like average date of last frost and lowest expected temperature for your area.

It's a good idea to estimate when it's a good idea to plant angel's trumpets by checking out the USDA zone info for Boulder.

Planting Calendar for Angel's Trumpets

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

You can plant angel's trumpets just a tiny bit earlier in the year because they are one of those plants that can tolerate a tiny bit of cold weather.

The earliest that you can plant angel's trumpets 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 angel's trumpets and expect a good harvest is probably August. If you wait any later than that and your angel's trumpets may not have a chance to really do well. You can get started a little bit earlier by starting your angel's trumpets indoors.

Last Frost Date

The average date of last frost is April 15 in Boulder. In the coldest months of winter you should expect an average low temperature of -15°F.

Always keep in mind that USDA zone info for Boulder may not be accurate from year to year and the actual date of last frost changes from year to year. Since half of the time in Boulder last frost occurs after April 15 be ready to cover your angel's trumpets if you have 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.