When can I plant Cosmos in Zone 5a

One of the first steps we take when we are making a decision about our gardening schedule is find our USDA Zone info. The zone info helps tell us things like average date of last frost and lowest expected temperature for our area.

The earliest that you can plant cosmos in Zone 5a can be figured out 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.

Cosmos do ok in a tiny bit of cold which means that you can plant them a bit earlier in the year 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 5a 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. If you wait 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 few weeks earlier.

Last Frost Date

The average date of last frost is April 15 in Zone 5a. It might get as low as -20°F during the coldest months of winter.

Always keep in mind that USDA zone info for Zone 5a may not be accurate from year to year and our actual date of last frost will vary from year to year. Since half of the time in Zone 5a we get surprised by a frost after April 15 be ready to cover your cosmos in the event of a late frost.

USDA Zone Info for Zone 5a

Here is the info for USDA Zone 5a.

Average Date of Last Frost (spring)April 15
Average Date of First Frost (fall)October 15
Lowest Expected Low-20°F
Highest Expected Low-15°F

This means that on a really cold year, the coldest it will get is -20°F. On most years you should be prepared to experience lows near -15°F.

Plants to Grow in Zone 5a

You may be interested in our other planting guides for Zone 5a.