When to Plant Cosmos in Brighton, CO

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.

The earliest that you can plant cosmos in Brighton can be estimated by reviewing the USDA zone info.


Planting Calendar for Cosmos

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

Cosmos do ok in moderate cold which means that you can start planting them slightly earlier than more sensitive plants.

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

The earliest that you can plant cosmos in Brighton 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 cosmos and expect a good harvest is probably August. You probably don't want to wait any later than that or else your cosmos may not have a chance to grow to maturity. You can get started a few weeks earlier by starting your cosmos indoors.

Last Frost Date

On average all chance of frost has passed is on April 15 in Brighton. 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 not always accurate because it is based on the USDA zone info for Brighton and it can change quite a bit from year to year. Half of the time in Brighton you get surprised by a frost after April 15 so just be sure to be ready to cover your cosmos if you have a late frost.

USDA Zone Info for Brighton

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 Brighton

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