Cosmos Flower - Growing Tips & Techniques

Cosmos Flower - Growing Tips & Techniques

Cosmos Flowers are annual plants that may be easily grown by scattering seeds in the garden after any threat of frost has gone. In around two months, these classic cottage garden flowers attain full maturity. 

The flowers perch atop long, thin stalks, forming a cloud of color that attracts bees, butterflies, and birds to your garden throughout the summer. Cosmos blooms resemble daisies in appearance. They appear in a variety of hues, and new varieties are being produced every year.

Cosmos Flowers are easy to grow from seeds, and they even thrive in poor soil  Here's how you can cultivate your own cosmos.

Common Types of Cosmos Flowers

There are more than 25 different species of cosmos. There are three primary species of Cosmos available to gardeners. We'll look at the characteristics of each.


Atrosanguineus, sometimes known as "chocolate cosmos," is a Mexican species with dark brownish-red flowers and even darker cores. The chocolaty aroma of these blossoms is true to their popular name.  Because the blooms are solitary, they are pollinator-friendly.

The blooms are borne on long stalks above the foliage and the leaves are tiny and lance-shaped, making them ideal for cut arrangements. These plants may reach a height of 30 inches with a spread of 18 inches.


Bipinnatus features wispy, threadlike leaves and flower heads that grow two to six inches across. This species' cultivars come in a wide spectrum of cool-toned hues, including pinks, purples, burgundies, yellows, and whites.

Single flowers with wide open petals are found in certain varieties, while frilly, semi-double flowers are found in others. Plants can grow up to six feet tall, depending on the cultivar.


C. sulphureus is endemic to Central America.  These cosmos flowers typically grow one to three feet tall with a two- to three-foot spread, although some types may grow up to six feet tall.

Blooms are two to three inches broad and come in a variety of colors including red, yellow, gold, and orange. C. sulphureus  cosmos have shorter stems than C. bipinnatus and C. atrosanguineus, making them less appealing as cut flowers.

The foliage is green and four to eight inches long, and the branching stems have an open, spreading growth pattern. The leaves of these plants, often known as "yellow cosmos".

Optimal Growing Conditions

Cosmos flowers are easy to cultivate in gardens and make excellent cut flowers. Plants that have been established can withstand drought, poor soil conditions, and general neglect. They even have the ability to self-sow. This plant is extremely low-maintenance.

While certain pests like cosmos, such as aphids and flea beetles they're easy to eliminate with a powerful spray of water or insecticidal soap.  Cosmos flowers should be spaced appropriately to enable adequate ventilation and minimize illness.


Cosmos plants thrive in neutral soil with a pH of 6.0 to 8.0, but they may also thrive in poor soil, where many blooming plants struggle. Cosmos thrive on medium-moisture, well-drained soils, although they may also thrive in dry conditions. 


Choose a location that receives full light for the finest blooming. Cosmos will thrive in partial shade, but will produce fewer flowers and be less vigorous. Like their original home, the desert parts of Mexico and Central America, these plants will grow in full sun for long periods of time under the warmest temperatures.


Unless there is a protracted drought, you will not need to water your cosmos flowers after they are established. Regular rainfall will be enough to keep your cosmos flowers growing beautifully.

Fertilizer & Nutrition

Fertilization can have a harmful influence on your cosmos flowers. Cosmos may grow in a variety of soil conditions. Fertilizer overuse might result in vigorous plants with a lot of foliage but few flowers. These plants do not require fertilizer unless they appear to be struggling.

How To Grow Cosmos Flowers

Cosmos flowers are easy to grow from seed, so if you're a new gardener, they are great flowers to start with. Follow these steps to start growing your own Cosmos Flowers:

  • Wait until your soil temperature reaches at least 60 or 70 degrees Fahrenheit, one to two weeks after your last normal frost date.
  • Add some compost to your beds, set aside a little amount of soil to cover the seeds, and smooth the soil down to make it level.
  • Water the dirt until it is damp on top.
  • Place a bunch of three seeds every nine to twelve inches and lightly cover them with dirt. Approximately 1/16th of an inch should be covering the seeds.
  • After seeding, seedlings should sprout in five to 21 days.
  • Keep the soil wet while the seeds germinate, watering daily if necessary.
  • As the sprouted seedlings grow established, reduce the frequency of your watering.

Cosmos flowers are simple to cultivate and doesn't need much attention. Giving it too much affection may produce issues.

Cosmos Flower - Care & Maintenance

Deadheading will help the plants blossom longer. This helps branching and accelerates flower development.

Staking may be required because some of these plants can grow to be quite tall. Protect them from severe winds by staking them or pinching out central shoots or stem points.

Water plants on a regular basis until they are established, or if the weather is exceptionally dry. Make sure you don't overwater your cosmos; excessive watering might cause the plants to produce fewer blossoms. 

Cosmos beds may grow weedy as a result of self-seeding, so remove blooms before they go to seed or thin seedlings in the spring. Keep your dog away from your new cosmos flowers.

Common Growing Issues With Cosmos Flowers

Cosmos are simple to grow and care for. Some pests can be a nuisance and impede their development.


There are two probable explanations if your plant gets enough of water and isn't withering from dehydration.  A common fusarium fungal infection can cause wilting and leaf discoloration in plants.

Fusarium is most likely present if you pull up the plant and discover a pink mass on the roots. The entire plant will die and must be destroyed to prevent the fungus from spreading.

If the roots are healthy when dug up, the plant may have a bacterial wilt infection. The bacterium causes wilting at the base of the stems. This plant will perish and should be removed from the environment.

Discoloration & Leaf Drop

Powdery mildew is mostly a problem for plants that grow in the shade. Fungus spores float in the air and land on a shaded host plant. It causes yellowing leaves and leaves to fall off by covering them with a powdery white coating. 

To avoid powdery mildew, give your plants plenty of air, strong light, and water the soil rather than the foliage. 

Stunted Growth

Cosmos flowers are susceptible to aster yellows, a disease carried by leafhoppers. The leaves will become mottled with yellow, and the blossoms will become deformed or stunted. 

Because there is nothing that can be done to assist these plants recover, they should be removed from your growing environment.


Cosmos may be employed in a variety of ways in the landscape. Use them in your landscape for a tall, wispy flower accent or bulk plantings for a powerful visual statement.

Tall cultivars should be planted in the rear of borders or as a primary focal point in mixed flower beds, while lesser types should be used in the midground or front.

These are a terrific alternative for gardens since they are easy to cultivate, and they are also a welcome addition to butterfly gardens or cut flower gardens.