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When to Plant Napa cabbage in Thornton, CO

One of the first steps you take when you are getting a good idea your gardening schedule is find your USDA Zone info. The zone info helps tell us things like average date of last frost and lowest expected temperature for your area.

By using the USDA zone info for Thornton you should be able to determine when it's possible to plant napa cabbage.

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Planting Calendar for Napa cabbage

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

You can plant napa cabbage quite a bit earlier in the year because they are one of those plants that can tolerate quite a bit of cold weather.

JanFebMarAprMayJunJulAugSepOctNovDec
Legend 
A good time to plant napa cabbage
Possibly ok, but a risky time to plant napa cabbage
Probably not a good time to plant napa cabbage

The earliest that you can plant napa cabbage in Thornton 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 really do well. If you are starting your napa cabbage indoors then you might be able to get away with starting them a few weeks earlier.

Last Frost Date

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

Remember that the actual date of last frost may not be accurate from year to year because it is based on the USDA zone info for Thornton and it can change quite a bit from year to year. Since half of the time in Thornton it frosts late in the year after April 15 be ready to protect your napa cabbage if you have a surprise late frost.

USDA Zone Info for Thornton

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 Thornton

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