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.

A common way of determining when it's the best time to plant cuphea is to use the USDA zone info for Boulder.

Planting Calendar for Cuphea

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

You should not plant cuphea until after the last frost when the weather gets warmer because they require warm weather.

The earliest that you can plant cuphea 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 cuphea and expect a good harvest is probably August. Any later than that and your cuphea may not have a chance to grow to maturity. You can get started a little bit earlier by starting your cuphea indoors.

Last Frost Date

On average the last frost when the weather gets warmer is on April 15 in Boulder. In the coldest months of winter you can expect an average low temperature of -15°F.

Since the USDA zone info for Boulder is just an average the actual date of last frost can change quite a bit from year to year. Half of the time in Boulder you get a frost after April 15 so just be sure to be ready to cover your cuphea if you have a 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.