Tropical Flowers

Cosmos Flowers – Common Problems and Solutions

Long, slender stems support bright, daisy-like annual flowers known as cosmos. They produce flowers throughout the summer and fall, bringing birds, bees, and butterflies to your yard. They are simple to grow from seeds and can even endure bad soil.

Flowers range in size from 3 to 5 inches and come in various hues, including pink, orange, red, yellow, white, and maroon. Their flowerheads might be formed like a bowl or an open cup. These lovely plants can grow up to 6 feet tall. Both beds and containers can be used to cultivate the cosmos, and they also make excellent cut flowers.

Although the cosmos can take longer to germinate, once it does, it blooms quickly and doesn’t stop until the fall. All summer long, the blossoms make a cloud of lovely color on top of long, slender stems that draw birds to your garden. Cosmos flowers resemble daisies in appearance.

Cosmos Care

Cosmos are simple to grow in beds and make excellent cut flowers. Once established, the plants can withstand neglect, drought, and poor soil. Even so, they self-sow. This plant requires incredibly little upkeep.

While some pests, such as aphids, flea beetles, and thrips, feed on the cosmos, they are simple to eradicate with an insecticidal soap or powerful water spray. Aster yellows, bacterial wilt may also impact Cosmos, and powdery mildew. Plants should be placed with adequate ventilation to prevent disease.

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Taller types complement goat’s beards, coneflowers, and black-eyed Susans well in the center or back of the border. Shorter varieties produce airy, vibrant edging plants.


For best flowering, choose a spot that gets direct sunlight. Despite having fewer blooms and being less vigorous when planted in shady places, the cosmos will still flourish in partial shade. Like their natural home, the desert parts of Mexico and Central America, these plants will flourish under the warmest temperatures with unbroken full sun.


Soil cosmos plants flourish in neutral soil with a pH range of 6.0 to 8.0, while many flowering plants struggle in poor soil. Although they can also operate effectively in dry soils, they perform best in medium moisture and well-drained soils. Plants may grow too tall and topple over if planted in rich soil. You can stop drooping by anchoring the plants or placing them adjacent to other plants that can sustain them.


Once your cosmos plants are established, you will only need to water them if there is a severe drought. These are the last plants in locations with scarce water resources that require irrigation.


Cosmos enjoy warm environments and can endure any humidity.


Fertilizing has a deleterious effect on the cosmos. Poor soil is no match for the cosmos. Strong plants with loads of foliage but few blossoms frequently result from too much fertilizer. These plants don’t require fertilizer unless they appear to be having difficulties.

Types of Cosmos

Over 25 different species of cosmos exist. However, gardens and landscaping most frequently employ three species. Mexico, Central America, and northern South America are the original home ranges of Cosmos sulphureus. It has golden yellow blossoms, is extremely drought resistant, and enjoys the heat. The flowering plant has semi-double and double flowers and is 2 to 6 feet tall. On average, some of the more recent cultivars have smaller, more orangish, and shorter blooms.

White, pink, red, and orange-colored Cosmos bipinnatus flowers resemble daisies and are quite colorful. They are shorter than C. suphureus, standing 1 to 4 feet tall, and come in several well-liked hybrid series. C. bipinnatus can thrive in almost any sunny area, albeit less heat tolerant than C. sulphureus.

Cosmos atrosanguineus, or chocolate cosmos, are a distinct species. The blossoms are dark crimson and have a chocolate scent. Despite being hardy to USDA zone 7, this perennial requires more upkeep than annual cosmos. It also grows from tubers, like dahlias.

Other typical cultivars of the cosmos are:

The “Bright Lights” mix boasts a combination of vibrant yellows, oranges, and reds.

The semi-double, vivid orange blossom known as “Cosmic Orange” is extremely drought tolerant.

The award-winning cultivar “Peppermint Candy” petals are splashed with magenta and white.

The tubular petals of Sea Shells Cosmos are unusual, and it has a lovely mixture of pastel colors.

‘Ladybird’ is a shorter type of cosmos that grows 18 to 24 inches tall and has red, yellow, orange, or gold blooms.


Deadheading will extend the flowering season and is the only basic maintenance for cosmos plants. When most of the flowers have faded, shear the plants by around one-third if you fall behind. A second flush of leaves and blossoms results from this type of pruning. By the end of the growing season, you can either pluck the plants up by their roots or cut them off at ground level. The plants might self-seed for the upcoming growing season if you leave them in their current location.


Self-seeding cosmo plants are easy to find. The optimal time to propagate these plants is once the risk of frost has passed. Although planting seeds is the best and simplest technique to multiply this plant, stem cuttings can also be used. Stem trims encourage the growth of additional leaves and flowers. The best propagation method for this plant, aside from seed, is stem cutting. How to do it is as follows:

You’ll need a sterile, well-draining potting soil and sterile pruning shears or scissors.

Put moistened potting soil in a tiny 3-inch container. Make a shallow hole in the ground by pushing down with the tip of a pencil about 1 to 2 inches deep.

Look for 3–5 leaf nodes on a cosmos shoot’s stem. Slice through the final leaf node. Remove the leaves at the final leaf node with care, preserving the node for future growth.

Insert the stem’s cut-off tip into the hole created by the pencil. Ensure that the final leaf node is elevated above the earth. To keep the stem erect and in place, compact the ground around it by pushing it down.

Water deeply and maintain moisture. Within three weeks, fresh leaf growth ought to be visible. If so, you can carefully remove the root ball from the container and move it to its new place.

How to Grow Cosmos From Seeds

Four to six weeks before the last frost, start seedlings indoors. Or, if you can directly plant cosmos in the garden outside after the risk of frost has passed. Don’t accelerate cosmos growth because a late frost can harm it. At 75 degrees Fahrenheit, they normally germinate in 7 to 21 days, then flower in around 50 to 60 days.

8 inches of dirt should be made loose. The seeds should be planted and covered with 1/4 inch of fine soil. Typically, seed packs advise specific spacing, like at 2-foot intervals. However, you can also scatter the seeds and allow the plants to support one another as they grow.

Potting and Repotting Cosmos

If you are growing cosmos in pots, check to see that the bottom of the container has drainage holes. Cosmos cannot tolerate too moist, muddy soil. Avoid enriching the soil if you’re growing in pots because it encourages tall, lanky, and droopy plant growth. Tall varieties will also require stakes in their containers. Consider utilizing a 12-inch-diameter, big container at a minimum.


An annual is Cosmos. They will perish if left outside in the cold. However, if you let the dead flower heads drop their seeds at the end of the flowering season, the cosmos seeds will hibernate and sprout in the spring when the earth warms up again.

You need a bright, full-sun growing lamp for at least 7 hours a day if you have a potted cosmos in a container and want to keep it alive during the winter. Any flowers that develop must be cut off as soon as possible. The flowering stage of this plant’s life cycle concludes with seed production for the following growing season.

How to Get Cosmos to Bloom

To blossom, cosmos plants require full sun. Even a slight shadow might prevent flowers from blooming. Deadheading the old blossoms is also necessary to promote new blooms. For faster flowering, prune in the space between the main stem and a leaf. The lower on the stem you cut the flowers, the longer they take to grow.

Common Problems With Cosmos

Throughout the growing season, cosmos are simple to grow and maintain. Although they often have a resistance to illness and the majority of insects, some pests can cause problems and stunt their growth.

Wilting or Leaf Discoloration

If your plant is getting enough water and isn’t wilting from dehydration, there are two potential reasons.

A typical fusarium fungal infection may be present in a plant that is withering and showing leaf discoloration.

Fusarium is probably present if you dig up the plant and find a pink mass on the roots. The entire plant should be destroyed to prevent the fungus from spreading because it will not survive.

The plant might have a bacterial wilt infection if the roots are dug out and appear in good condition. The bacteria make the base of the stems wilt. This plant needs to be removed since it will perish.

Yellowing Leaves and Leaf Drop

Plants in the shade are primarily affected by powdery mildew. Airborne fungus spores land on a host plant in a moist environment. It causes leaves to become yellow and fall off, and it coats them with a powdery white covering. Give your plants plenty of airflows, and strong light, and avoid watering the leaves to prevent powdery mildew. Use a horticultural fungicide as directed on the label if your plant has fungus.

Flowers Distorting or Stunting in Growth

Cosmos, a plant in the aster family, is susceptible to the disease of aster yellows, which is spread by leafhoppers (a tiny grasshopper-looking insect). The flowers will seem deformed or stunted, and the foliage may develop yellow spotting. Since you can do nothing to help these plants recover, dispose of them.


Cosmos flowers are a must-have for many summer gardens since they grow to different heights, come in a variety of hues, and give the flower bed a frilly texture. When single or double flowers occur on stems that grow 1 to 4 feet in length, cosmos flower cultivation is straightforward, and cosmos flower maintenance is simple and rewarding (0.5-1 m.).

Taller cultivars may require staking if they are not planted in a wind-protected region. Cosmos flowers can be grown for various purposes, including backdrops for other plants and cut flowers for indoor displays. Even screens made of cosmos can be utilized to cover undesirable landscape features.

Place cosmos flowers in heavily amended soil when you are planting them. The best conditions for growing the cosmos are hot, dry weather and poor to ordinary soil. Typically, cosmos plants are cultivated from seeds.


Are the cosmos easy to care for?

Yes. Cosmos are simple to take care of, self-seed for the following growing season, and germinate easily.Yes. Cosmos are simple to take care of, self-seed for the following growing season, and germinate easily.

How fast do the cosmos flowers grow?

Cosmos typically germinate in 7 to 21 days and flower 50 to 60 days after planting.

How long can the cosmos live?

An annual plant called cosmos sprouts, blooms, and sheds seeds to get ready for the following growing season. After blossoming, cosmo will sag and eventually die.