When can I plant Cosmos in Zone 1a

Before planting it is a good idea to find our USDA Zone info to determine our garden schedule. The most important data that the zone info tells us is average last frost and the lowest expected temperature for our area.

The earliest that you can plant cosmos in Zone 1a 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 you should plant them: Up to 3 weeks before last frost.

Since cosmos do ok in moderate cold you can plant them just a tiny bit earlier in the year than other frost tender 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 Zone 1a 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. Any later than that and your cosmos may not have a chance to fully mature. If you are starting your cosmos indoors then you might be able to get away with starting them a couple of weeks earlier.

Last Frost Date

On average the last frost when the weather gets warmer is on June 15 in Zone 1a. In the coldest months of winter we can expect an average low temperature of -60°F.

Since the USDA zone info for Zone 1a is just an average our actual date of last frost can change quite a bit from year to year. Since half of the time in Zone 1a we get a frost after June 15 be ready to protect your cosmos if we have a late frost.

USDA Zone Info for Zone 1a

Here is the info for USDA Zone 1a.

Average Date of Last Frost (spring)June 15
Average Date of First Frost (fall)July 15
Lowest Expected Low-60°F
Highest Expected Low-55°F

This means that on a really cold year, the coldest it will get is -60°F. On most years you should be prepared to experience lows near -55°F.

Plants to Grow in Zone 1a

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