One of the best tools that you have as gardeners to help us figure out your gardening schedule is the USDA zone info. The zone info helps tell us things like average date of last frost and lowest expected temperature for your area.

In Denver you can figure out when it's the best time to plant napa cabbage by referring to the USDA zone info.

Planting Calendar for Napa cabbage

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

Since napa cabbage are one of those plants that can tolerate quite a bit of cold weather 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 napa cabbage in Denver 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 napa cabbage and expect a good harvest is probably September. You probably don't want to wait any later than that or else your napa cabbage may not have a chance to grow to maturity. You can get started a couple of weeks earlier by starting your napa cabbage indoors.

Last Frost Date

On average all chance of frost has passed is on April 15 in Denver. In the coldest months of winter you can expect an average low temperature of -15°F.

Since the USDA zone info for Denver may not be accurate from year to year the actual date of last frost is different every year. Half of the time in Denver you get surprised by a frost after April 15 so be sure to be ready to protect your napa cabbage if you have a surprise late frost.

USDA Zone Info for Denver

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 Denver

You may be interested in your other planting guides for Denver.