When can I plant Cosmos in Zone 1b

One of the best tools that we have as gardeners to help us determine our gardening schedule is the USDA zone info. The zone info helps tell us things like average date of last frost and lowest expected temperature for our area.

The USDA zone info for Zone 1b can be looked at to estimate when it's possible to plant cosmos.


Planting Calendar for Cosmos

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

Cosmos are one of those plants that can tolerate a tiny bit of cold weather which means that you can get them planted just a bit earlier than other plants that might not handle the cold.

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 Zone 1b is June. However, you really should wait until July if you don't want to take any chances.

The last month that you can plant cosmos and expect a good harvest is probably July. You probably don't want to wait any later than that or else your cosmos may not have a chance to grow to maturity. If you are starting your cosmos indoors then you might be able to get away with starting them a few weeks earlier.

Last Frost Date

The average date of last frost is June 15 in Zone 1b. We should expect an average low temperature of -55°F in the coldest months of winter.

Just be sure to remember that USDA zone info for Zone 1b may not be accurate from year to year and our actual date of last frost is different every year. Half of the time in Zone 1b it frosts late in the year after June 15 so make sure that you are prepared to protect your cosmos if we have a surprise late frost.

USDA Zone Info for Zone 1b

Here is the info for USDA Zone 1b.

Average Date of Last Frost (spring)June 15
Average Date of First Frost (fall)July 15
Lowest Expected Low-55°F
Highest Expected Low-50°F

This means that on a really cold year, the coldest it will get is -55°F. On most years you should be prepared to experience lows near -50°F.

Plants to Grow in Zone 1b

You may be interested in our other planting guides for Zone 1b.