Planting cosmos flowers – how to plant, grow and care for cosmos


Cosmos is an annual flower that looks beautiful as a tangled flower in an informal planting or cottage garden setting. This beautiful plant is a low-maintenance summer flower with colorful flowers atop tall, delicate stems. They are the perfect addition to a sunny meadow garden.

Flowers are great food for bees and can make fantastic cut flowers for informal style bouquets for home use. A low-maintenance flower choice for those who want vibrant flowers without much effort.

Adorable cosmos flowers with bright pink petals in a transparent glass vase.

planting komos in the garden

You will not be disappointed by planting cosmos in your garden. The plant produces brilliantly colored flowers on large, delicate stems. The cosmos’ huge nature is not suitable for formal beds, but it does shine on informal plants.

Cosmos belongs to the daisy family. Both cosmos species look like typical daisy-type flowers with a yellow center surrounded by colorful petals called stingray flowers. Flowers are single or double and up to 4 inches tall. Both species bloom from early summer to the first frosts.

Cosmos flowers are native to Central America and Mexico. Therefore, they are sometimes called Mexican Asters. There are two kinds of universe.

Seed. bipinnatus (Common Garden Cosmos). tall breed Cosmos bipinatus Grows 4-6 feet with a spread of 1-3 feet. The dwarf variety grows to 3-3.5 feet. Flowers are dark pink, pale pink, white and fuchsia.

Seed. brimstone (yellow cosmos). tall breed cosmos sulphureus will grow 2-6 feet with a spread of 1-3 feet. Dwarf varieties grow 1-2 feet with a 1-3 foot spread. Flowers are gold, yellow and orange.

For both types of cosmos, taller varieties may need support to keep them from overturning in strong winds.

Cosmos planted in a flower garden.

Grow cosmos flowers in the right environment.

As with almost all flowers, the secret to growing cosmos is to ensure the right environment for the flower to thrive. This daisy-like flower blooms from early summer to late summer, sometimes into early fall.

Tall plants look lovely when planted in single bulk in the garden or behind larger informal flower beds and borders. Short varieties of this annual plant are beautiful on the edge and front of garden beds. During the flowering period, it looks beautiful even in containers and window boxes.


Cosmos flowers are soft annuals and do not tolerate even light frosts. But as long as you remove the flowers, they will bloom all summer.


Cosmos is a sun-loving plant that likes hot, dry environments. They do best in full sun, but will tolerate partial shade. For abundant flowering, plant in a sunny place with afternoon sun.


Like nasturtium, cosmos prefer poor soil. Fertile soil will lead to plants with many green leaves at the expense of flowers. Plant in dry, fertile soil for best flowering.

The soil should be well-drained with a pH in the 6-8 range.

Field of pink and white cosmos.

Planting and breeding cosmos

Cosmos is one of the easiest plants to grow. You can start indoor seeds for earlier flowers or sow them directly into your garden. It couldn’t be easier than this!


If sowing outdoors, wait until all risk of frost is gone.

Seed can be started indoors for 4-6 weeks in early spring before the last frost in your area. Cosmos seeds are sown on flat ground, but only cover the seeds with soil. Keep the soil warm as cosmos seeds need heat to germinate. Seeds should germinate in 4-7 days.

Space plants are 8-16 inches apart, depending on height at maturity.


In warm regions with mild winters, cosmos is sown annually. Seeds can also be collected after the first frost when the flower heads dry out. Store the seeds in dry seed packets or bags for planting next spring.

container gardening

Plant small varieties such as: sonata in container. As long as the soil is not fertile, cosmos will grow well in containers.

Cosmos flowers blooming in the garden summer season.

Cosmos recommended varieties

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There are so many types of cosmos to try. We have listed the ones we personally grew up and loved.

bright light – Classic sulfur cosmos with glowing flowers in shades of yellow, gold, orange and scarlet. Ht 36-48 inches tall.

piper – It is a shellfish flower characterized by deep reddish brown with grooved petals and soft creamy pinkish white. Ht. 36-40 inches tall.

double click – These flowers are great for trimmed gardens. Fluffy, powder-puppy-style flowers fill the bouquet with rich color and texture. Colors range from dark maroon to pink, purple and white. Ht. 24-31″. Double Click is our garden’s #1 moving flower.

purity – This is the flower you want to plant in the moonlit garden. The Flower of Innocence is a dazzlingly bright white flower, especially when lit by the moon. Ht. 30-36″. These flowers are a great addition to your moonlight garden.

ruby – The darkest red of all the universe. The flowers hang on tall, delicate stems and are a stark contrast to the bright green lace leaves. They are the absolute beauty of mass-planted gardens. Ht. 36–48″

Cosmos looks beautiful with hosta, snapdragon, forget-me-not, zinnia, dahlia and marigold planted.

Fuchsia colored cosmos flower isolated on white background.

caring for the universe

The secret to any flower you grow in your garden is to ensure the plant has the right conditions to thrive. Not all plants like the same thing, so learn to care for each species individually.


Cosmos require an inch of water per week, either through rain or manual irrigation.


No need to fertilize cosmos plants. They like poor soil and do not bloom well when fertilizer is added to the soil. Planting cosmos in fertile soil results in large, leafy plants that rarely flower.

Flowering and Drying – How to Enjoy Cosmos Flowers

The growing universe is a wonderful pastime in the summer. The more you cut it, the more flowers bloom. Plant about 12 seeds and you will have a fresh bouquet every week at home. We love the cut flower garden and like to save some flowers to dry for crafts in the fall and winter.

cut flowers

Cosmos makes beautiful cut flowers. Every year, we grow “double click” and “purity” in our cutting garden. Cut flowers last about 4-6 days, but the stems have flowers that open individually over the course of a week. Use a flower preservative in your water.

Cosmos is usually Atrosanguinian Cosmos (Chocolate Cosmos). These dark red flowers have a distinctive chocolate flavor.

see: Best flowers for your cutting garden


Cosmos has poor air permeability, so you can dry it with silica gel. Cosmo flowers are also pressed well, but drying with silica gel will help retain the color much better than pressing.

check out our post how to dry flowers.

Bright pink cosmos on a bright white background.

common pests

Cosmos, like most annuals, can suffer from many types of garden pests.


Aphids will distort the growth of the plants they infect. The leaves may curl or atrophy and turn yellow.

Remove the aphids by vigorously spraying water on the underside of the leaves or using insecticidal soap.

Japanese beetle

Japanese beetles eat leaves and destroy flowers. They are shiny, metallic green beetles that are 1/2 inch long and have copper-colored wings.

To control beetles, hand-pick the beetles from the plant, crush them, or drop them into a bucket of soapy water.

For severe infections, spray worm-infected plants every 3-5 days. Reptiles are harmful to bees and pollinators, so spray after 9pm and before 5am to avoid harming beneficial insects.


If your cosmos plant suddenly withers and falls, take a closer look at the stems for small round holes.

Eliminate and destroy plants infected with the borer.

Prevention is the best defense against borers. Clean and burn or destroy all weeds and debris.

Bt (Bacillus thuringiensis) is effective early in the season.

A single bright pink cosmos flower on a bright white background.

Common diseases affecting the universe

Many fungal and bacterial diseases can affect cosmos. Understanding what to look for when diagnosing a disease is the first step to helping control the spread in your garden.

wilting bacteria

Bacterial wilting may be suspected if the plant turns yellow and wilts. You can check the cosmic bacterial wilting by cutting off the stem close to the root. If a lump of gray bacteria oozes out, you have a fungal disease known as bacterial wilt.

Overcrowding and excessive watering are two common causes of bacterial wilting in gardens. Do not plant cosmos too close or in flooded areas.

Completely remove infected plants from the garden, including the soil in which the plants were growing. Do not compost it, put it in a tied plastic bag and throw it in the trash.

Garden tools should be disinfected after cutting plants infected with bacterial wilt.

stem cell pathology

Stem ulcers are easy to find in space. First, dark brown spots appear on the stems that turn gray, which is a sure sign of Canker. Eventually, the canker wraps around the stem and breaks it, causing the plant to wither and die.

To control the presence of stem germs in your garden, remove and destroy all infected plants. Do not put it in the compost bin.

All tools and equipment used to remove stem cankers must be disinfected to prevent the stem canker from spreading.

powdery mildew

If you see white spots on cosmos leaves, powdery mildew may be the cause. Although generally not a threat to plant health, powdery mildew can dry or wil the leaves.

For control, quickly remove the affected leaves to contain the pathogen.

Cosmos growing in home garden

Planting cosmos is an easy way to get beautiful, colorful flowers in your flower garden. They don’t require much maintenance or expensive fertilizers, and they have low maintenance throughout the season. I hope you’ve learned everything you need to get started with one of my favorite flower species!

Looking for more flower growing posts?

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