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.

The earliest that you can plant lunaria in Boulder should be determined by reviewing the USDA zone info.

Planting Calendar for Lunaria

Frost tolerance for lunaria:	Tolerant of some frost.
When to plant:	Up to 5 weeks before last frost.

Lunaria are moderately cold tolerant which means that you can plant them earlier than other frost tender plants.

The earliest that you can plant lunaria in Boulder is February. However, you really should wait until March if you don't want to take any chances.

The last month that you can plant lunaria and expect a good harvest is probably September. Any later than that and your lunaria may not have a chance to really do well. If you are starting your lunaria indoors then you might be able to get away with starting them a few 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 make sure that you are prepared to protect your lunaria in the event of 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.