One of the first steps you take when you are making a decision about your gardening schedule is find your USDA Zone info. The most important data that the zone info tells us is average last frost and the lowest expected temperature for your area.

The USDA zone info for Thornton should be used to figure out when it's possible to plant monarda.

Planting Calendar for Monarda

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

Since monarda are one of those plants that can tolerate a tiny bit of cold weather you can plant them a bit earlier in the year than other plants that might not handle the cold.

The earliest that you can plant monarda 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 monarda and expect a good harvest is probably August. Any later than that and your monarda may not have a chance to grow to maturity. You can get started a couple of weeks earlier by starting your monarda indoors.

Last Frost Date

In Thornton the average date of last frost happens on April 15. You can expect an average low temperature of -15°F in the coldest months of winter.

Just be sure to remember that the actual date of last frost is just an average because it is based on the USDA zone info for Thornton and it is different every year. Since half of the time in Thornton it frosts late in the year after April 15 be ready to cover your monarda 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.