Cosmos (*Cosmea bipinnata*) is a total powerhouse in the garden—it blooms its heart out all season long and is incredibly low-maintenance. If you’re looking for the perfect summer flower, this is it! The only real “must-have” for Cosmos is plenty of sunlight. Give them that, and they’ll reward you with a colorful explosion of blooms all summer.
Cosmos Craves the Sun
To really get that lush carpet of flowers we all love, you’ll want to plant your Cosmos in a sunny spot. If they’re stuck in the partial shade, they’ll spend more energy on leaves and way less on those beautiful blossoms.
As far as soil goes, they thrive in loose, moderately moist ground. But honestly? These summer beauties aren’t picky. They’ll grow in almost any potting soil, provided it isn’t over-fertilized. If you’re planting them in containers, I recommend using a peaty potting mix blended with a little sand for drainage.
Sowing Seeds Directly in the Garden
Getting these started is a breeze. You can simply scatter the seeds directly into your flower beds in early May. If you go this route, you can expect to see those delicate, feathery blooms starting in August.
Start Seeds Indoors for Earlier Blooms
If you’re like me and can’t wait until late summer to see some color, you should definitely start your Cosmos indoors.
You don’t need to run out and buy nursery starts, either—growing them yourself is super easy. You can grab a seed packet at the store or even harvest seeds from last year’s plants.
Here’s how to do it:
- Starting in March, sow the seeds in trays using a low-nutrient seed-starting mix (or just mix some regular potting soil with a bit of sand).
- After about four weeks, “prick out” the seedlings and move them into their own individual pots.
- Keep them in a bright spot at around 60°F (15°C), and they’ll grow into nice, sturdy little plants.
- Come May, they’re ready for the garden or your patio containers. Just a heads-up: Cosmos are very sensitive to the cold! Make sure you wait until the danger of night frost has passed before moving them outside.
- When you do plant them, give them some elbow room—about 12 inches (30 cm) apart. These plants need space because, depending on the variety, they can grow anywhere from 15 inches to a whopping 6 feet tall!
