Do you want to grow cosmos in Illinois, but don’t know when to plant them?
Planting cosmos is not as easy as it seems.
Here’s why:
- Cosmos are not able to survive frost or cold weather under 50 degrees Fahrenheit.
So if you plant them outside too early in the spring they will die. And if you plant them too late, your cosmos won’t produce a bloom.
Today, I’m going to teach you the ideal time to plant cosmos in Illinois:
- To Learn More About HOW to Grow Cosmos, Check Out This GUIDE!
When to Plant Cosmos in Illinois
As you may have already guessed, you need to pay very close attention to your local weather in the spring. Specifically, you are going to need to watch when the last frost occurs.
In general, when there hasn’t been a frost for two weeks, you are SAFE to plant your cosmos outside in Illinois!
For your reference, I have created this table for average frost dates for most major cities in Illinois. If your city is not listed below you can find its Last & First Frost Dates HERE.
Illinois Last & First Frost Dates
Unfortunately, Mother Nature plays cruel tricks on us every year.
It should be noted that the above dates are just averages.
There are years when the last frost comes MUCH later. Sometimes, the last frost happens much earlier and you can get your cosmos planted outside in Illinois much quicker.
Like I said before, you need to be very diligent in checking your local weather.
So what happens if a frost comes AFTER you plant your cosmos?
When you know a frost is coming you need to take action.
- If cosmos are in pots, bring them inside
- If cosmos are in the ground, cover them in burlap and hope they survive
Also, make sure not to plant your cosmos in your garden too late.
- Planting cosmos too late will cause small blooms or even worse, no blooms.
When Should You Start Your Cosmos Seeds Indoors?
Depending on the type of cosmos, it takes roughly 7 to 10 days to grow cosmos from seed indoors and then transplant them to your garden. And then another 3 months to bloom!
For a specific date that you should start cosmos seeds indoors you should:
- Find the last average frost date HERE
- And then subtract 7 days from it
Not only this, but I recommend again paying close attention to your local weather report.
It should also be noted that the best technique for bringing your cosmos plants outside is to introduce them (in their pots) outside for an hour. And then increase the amount of time they spend outside each day by an hour until they have been outside for 8 hours.
This will “harden” your cosmos plant, increasing its chances of fighting off diseases, insects, droughts, and wet conditions.
If you want to learn WHEN to plant ANY Flower in Illinois, head over to HERE and just type in the flower you want to grow.
