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.

It's possible to estimate when to plant trifolium by using the USDA zone info for Thornton.

Planting Calendar for Trifolium

Frost tolerance for trifolium:	Tolerant of a very small amount of frost.
When to plant:	Up to 3 weeks before last frost.

Since trifolium are barely cold tolerant you can plant them just a tiny bit earlier in the year than plants that are more sensitive to the cold.

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

The last month that you can plant trifolium and expect a good harvest is probably August. Any later than that and your trifolium may not have a chance to really do well. If you are starting your trifolium 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.

Keep in mind that the actual date of last frost is just an average because it is based on the USDA zone info for Thornton and it changes from year to year. Half of the time in Thornton it frosts late in the year after April 15 so make sure that you are ready to cover your trifolium if you have 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.