Before planting it is a good idea to find your USDA Zone info to figure out 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 possible to determine when you can plant carnation by referring to the USDA zone info for Boulder.

Planting Calendar for Carnation

Frost tolerance for carnation:	Very tolerant of frost.
When to plant:	Up to 7 weeks before last frost.

Carnation can survive in a bit of cold which tells us that you can plant them a lot earlier in the year than plants that are more sensitive to the cold.

The earliest that you can plant carnation 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 carnation and expect a good harvest is probably September. If you wait any later than that and your carnation may not have a chance to grow to maturity. You can get started a few weeks earlier by starting your carnation indoors.

Last Frost Date

In Boulder the average date of last frost happens on April 15. It might get as low as -15°F during the coldest months of winter.

Keep in mind that USDA zone info for Boulder is an average and the actual date of last frost can change quite a bit from year to year. Half of the time in Boulder you get surprised by a frost after April 15 so be sure to be ready to cover your carnation if you have 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.