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

By looking at the USDA zone info for Thornton it's a good idea to determine when you can plant asparagus.

Planting Calendar for Asparagus

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

Asparagus do ok in pretty solid cold which tells us that you can plant them much earlier in the year than plants that are more sensitive to the cold.

The earliest that you can plant asparagus 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 asparagus and expect a good harvest is probably September. You probably don't want to wait any later than that or else your asparagus may not have a chance to fully mature. Starting your asparagus indoors is a great way to get them started a few weeks earlier.

Last Frost Date

On average the last frost is on April 15 in Thornton. It might get as low as -15°F during the coldest months of winter.

Since the USDA zone info for Thornton is just an average the actual date of last frost can change quite a bit from year to year. Half of the time in Thornton there is a last frost after April 15 so make sure that you are ready to protect your asparagus in the event of one of those late frosts.

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.