Plant cosmos provides harmony in the garden

story tease

By Terry Shears

OSU Ext. master gardener volunteer


They attract pollinators, are great cut flowers, are of no interest to most pests – including the four-footed kind, are easy to grow and thrive on neglect. So what is this super flower?

“Cosmos” is the Greek word for harmony or an ordered universe. It’s also the name of this easy-to-grow flower that will be blooming in our area soon. It’s also called the Mexican aster because Spanish priests used to grow cosmos in their mission gardens in Mexico, taking advantage of the hot, dry conditions they like.

Cosmos are a solitary flower with a single row of petals in white, yellow, red and pinks, surrounding a yellow center.

Along with marigolds, zinnias, and sunflowers, they attract pollinators like honeybees, native bees, butterflies, moths, and hummingbirds to your garden. If they are cut and brought into the house, they can last four to six days in a vase.

Here in Ohio, they thrive as an annual that is really easy to grow. Simply scatter seeds after the danger of frost has past in an area of full sun, if possible. Just rake the seeds into loose soil. If you plant the seeds too deep, germination will be slowed.

Keep the soil moist for about a week after planting and look for sprouts one to three weeks later. It will take about 50 to 55 days for the plants to start setting buds. Mine were about two feet high at the beginning of July and thriving in the current hot conditions!

They require little maintenance. Don’t worry about watering them unless there is a severe drought. Even then if you don’t water they probably won’t care. Allow some room as they can grow two to five feet tall and spread one to two feet. Because they are so tall they can flop over, so grow them closely together or near other plants or plan to stake them.

Deadheading is very effective with cosmos and prolongs their flowering season. If you get behind, just shear the plants back by about one-third when most of the flowers have faded, and they will produce a second array of leaves and flowers.

Cosmos are annuals here, self-seeding in warmer climates, but we can easily harvest the dried seeds after the plants are spent and plant them the next growing season.

Deer and other four-footed critters show little interest in cosmos, and winged pests don’t either (except for aphids from time to time that can be simply sprayed off with the hose). Thankfully so, because they are missing out on a great garden treasure that we get to enjoy instead.

Details and cultivar suggestions are available at:

More like this from

Subscribe Today

Sign up for our email newsletter to receive daily news.

Want more? Click here to subscribe to either the Print or Digital Editions.