The USDA Zone info is a great tool for gardeners to help us determine your gardening schedule. The zone info helps tell us things like average date of last frost and lowest expected temperature for your area.

It's possible to figure out when you can plant gomphrena by checking out the USDA zone info for Boulder.

Planting Calendar for Gomphrena

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

You can plant gomphrena a bit earlier in the year because they do ok in moderate cold.

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

Remember that USDA zone info for Boulder is just an average 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 gomphrena 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.