Cosmos Plant: How To Grow Brilliant Flowers

The explanations so as to add the cosmos plant to your backyard are nearly countless. They make nice reduce flowers, they’re low upkeep, they usually appeal to butterflies and different helpful bugs. You’ll be able to develop them in a devoted flower mattress or interplant them amongst your vegetable crops to take full benefit of the helpful bugs that they appeal to to help in pest administration. Cosmos are very simple to develop and produce tons of attractive flowers! 

They are often simply began from seeds indoors and transplanted within the early spring after the final frost. They may set up in spring and are available into full bloom as part of the summer time backyard. As part of the aster household, cosmos flowers have a daisy-like look and are available a wide range of colours. They’re simply recognized by their blooms and feathery, fern-like foliage. They arrive in dwarf varieties and tall varieties, and there’s a cosmos for each location in your backyard. 

The cosmos flower readily self-seeds and may create a stand that can come again yr after yr. The flower heads are additionally simple to gather on the finish of the season when you’d like to gather seeds and sow them in one other space of your backyard. Sow cosmos seeds in any case hazard of frost, as they require temperatures close to 70 levels Fahrenheit and constant moisture with a purpose to germinate. Additionally, reference your seed packets for the precise germination necessities of the range you propose to develop. 

Fast Care Information

Cosmos. Supply: Nico_Alonso
Frequent Title Cosmos, backyard cosmos, Mexican aster, sulfur cosmos
Scientific Title There are a lot of totally different cosmos varieties corresponding to cosmos sulphureus, cosmos bipinnatus, cosmos atrosanguineus. All of them have comparable care necessities. 
Household Asteraceae, the identical household as sunflowers and daisies.
Top & Unfold 12 to 36 inches tall with a 3ft unfold. Some varieties, nevertheless, can develop 50 inches tall! 
Mild Full daylight, however can tolerate gentle shade in areas with excessive warmth
Soil Dry, arid soil. Accepts poor soil situations.
Water Drought tolerant. 
Pests & Illnesses Aphids, thrips, aster yellows, powdery mildew

All About The Cosmos Plant

C. sulphureus
C. sulphureus. Supply: Dinesh Valke

There are over 30 identified species of the plant cosmos. Together with different crops like them, they’re native to clean and meadowland in Mexico, Central America, and South America. These daisy-like flowers – generally known as the Mexican aster – lengthen as far north because the Olympic Peninsula in Washington. Cosmos bipinnatus has even naturalized within the Japanese United States and Japanese Canada. 

Most cosmos flowers are annuals. Nevertheless, there are additionally perennial varieties corresponding to C. atrosanguineas, also called chocolate cosmos. Though they’re perennial, they’re nonetheless extraordinarily frost tender and may solely be grown as perennials in USDA zones Sept. 11. If they’re effectively mulched, then they’ll probably survive in USDA zones 7-8. Annual cosmos could be grown in USDA zones 2-11. 

Many gardeners develop cosmos flowers for his or her daisy-like form. The cosmos flower sits atop slender stems which might be 12 to 50 inches tall and adorned with fern-like feathery foliage. Younger crops could be planted outdoors as soon as the hazard of frost has handed within the spring. From their first bloom, they are going to proceed to supply flowers till the primary fall frost. 

The Mexican aster can also be edible, and the flower petals could be added to salads. They don’t add a lot taste, however they do add a splash of shade! The title cosmos comes from the Greek phrase Kosmos which suggests “order” and is claimed to check with the orderly association of their petals. 

Forms of Cosmos

As talked about above, there are over 30 totally different species of cosmos and a number of varieties and cultivars inside every species. That being mentioned, a number of species of this plant sort are noteworthy as they’re extra standard and extra extensively obtainable to dwelling gardeners.

Cosmos bipinnatus

A typical vary of colours for the Cosmos bipinnatus species consists of double blooms in shades of purple, pink, and white. Due to their flower shade, this species is especially good at attracting butterflies to your backyard. They make a superb addition to a butterfly backyard. Their semi-double flowers may also self-seed profusely, which tends to draw birds searching for a snack on the finish of the rising season. The ocean shells cultivar even has tubular petals that brighten up the backyard.   

Cosmos atrosanguineas

Also referred to as chocolate cosmos, this can be a perennial selection in USDA zones Sept. 11. In zones that obtain frost, their tubers could be dug up from the flower mattress like different crops with bulbed roots and moved to a frost-free space for storage over the winter. They will then be replanted within the spring (very similar to Dahlias). Their title comes from their shade which usually ranges from darkish crimson to black. In addition they have the biggest flower head of all cosmos species at 5 cm in diameter. 

Cosmos sulphureus

C. sulphureus’ double blooms are available a wide range of colours, however the commonest shade is yellow. Their younger shoots are eaten uncooked or cooked in Indonesia and in Thailand, they’re consumed in salads or brewed in teas. The intense lights combine has an array of yellow and orange related to it. Due to their shade, the daisy-like flowers have additionally been used to create an orange-yellow dye that was used to dye wool in pre-Colombian America and later South America. 

Caring for Cosmos Crops

Chocolate Cosmos
Chocolate cosmos. Supply: wallygrom

Cosmos flower care is comparatively simple, and as soon as your flowers are established, you’ll take pleasure in their blooms all season lengthy! Learn to learn to present cosmos flowers with their excellent rising situations and encourage extra blooms. 

Solar and Temperature

Plant cosmos in full solar areas that obtain 6-8 hours of direct daylight per day. Nevertheless, since they are often grown in USDA zones 2-11, this suggestion can differ relying on the place you might be. In cooler or extra temperate areas, it’s greatest to comply with the complete daylight requirement. It’s best to offer your cosmos with gentle shade in areas that obtain excessive warmth throughout the summer time. 

If you develop cosmos, excessive warmth (above 90 levels) for prolonged intervals of time will drastically cut back the variety of blooms. Germination happens at 75 levels, and 75-85 levels is the best rising temperature for younger crops. These frost-tender annuals can’t survive even gentle frosts of 32 levels Fahrenheit. In exhausting frosts, they could die. At this level within the rising season, it’s greatest to let the crops go to seed and accumulate the seeds for subsequent yr. 

Water and Humidity

Water your rising cosmos within the morning or later within the afternoon after the warmth of the day has handed to keep away from dropping moisture to evaporation. Keep away from soaking the entire plant and water straight on the base. It will assist keep away from potential fungal points with the foliage. That is particularly necessary in areas with excessive humidity. 

When you develop cosmos in an space with a moist local weather, you may additionally wish to think about rising the spacing between crops to assist with air circulation and stop illness. Because the seeds germinate, it’s necessary to maintain the soil moist. Proceed to water younger crops commonly whereas they turn into established. 

As soon as cosmos attain maturity and start to develop cosmos flowers, they’ll turn into fairly drought tolerant and may survive on a deep watering as soon as each two weeks. Cosmos crops thrive in dry and arid situations. 


Candystripe Cosmos
Candystripe Cosmos. Supply: Dane Vandeputte

One of many issues that makes rising cosmos really easy is their skill to tolerate poor soil situations. They like well-draining, sandy, impartial to alkaline soil. Crucial factor is sweet drainage. Cosmos and cosmos seeds don’t do effectively in standing water or repeatedly moist soil. 

Compost or natural matter could be added to the planting website previous to planting, though this isn’t required. When rising cosmos in pots, you’ll want to amend the potting soil with perlite or vermiculite to extend drainage since most potting soils are made to retain moisture. 

Fertilizing Cosmos

As talked about above, cosmos crops can survive poor soil situations and don’t require soil amendments with a purpose to thrive! Actually, the addition of fertilizers can encourage foliage progress on the expense of blooms. That is very true with nitrogen-heavy fertilizers. 

Because of this, it’s not really useful to fertilize cosmos flowers. The addition of compost on the planting website firstly of the rising season, while you plant seeds, will present all of the vitamin that these crops require. 

Pruning Cosmos Crops

Cosmos crops profit drastically from common pruning of lifeless flower heads. Eradicating flowers as they fade will assist encourage progress and extra flowers. It will come simply when you’re one of many many gardeners which have added the cosmos flower to your panorama to be used as a reduce flower. Don’t be shy about slicing them again and bringing the flowers inside for a good looking bouquet. Your crops will thanks by producing much more flowers. 

If you’re rising cosmos, apart from deadheading, they don’t require further pruning. Nevertheless, cosmos flowers can develop a number of ft tall, and offering some taller varieties help like staking could be helpful, particularly in areas with excessive winds. In areas that obtain heavy rains, some stem breakage could also be unavoidable, even when you give cosmos crops help. 

Cosmos Plant Propagation

Whereas cosmos can self-seed, they’ll simply be propagated from stem cuttings. Take a slicing just under a leaf node. Take away the decrease foliage and both place the slicing right into a glass of water or straight into the soil. If positioned straight into the soil, it’s best to count on to see new progress inside 3 weeks. When putting the slicing right into a glass of water, you will notice root progress seem over a number of weeks, after which you’ll be able to select to transplant your slicing into the bottom. 

Cosmos don’t significantly like being transplanted because the roots could be delicate. Because of this, rising cosmos crops from seed is the standard methodology of propagation. Scatter seeds onto a naked space and calmly rake them in along with your fingers. As soon as planted, this annual flower self-seeds and can proceed to offer extra cosmos flowers in that space for years to return. 

Repotting a Cosmos Plant

When you’ve chosen to develop your cosmos flowers in a container then you might be asking whether or not repotting is critical. As talked about above, the foundation ball could be delicate to transplant, so it’s greatest to keep away from this by rising it within the appropriate-sized container from the beginning. 

Nevertheless, if you’re rising a perennial selection, you might come to a time when it’s worthwhile to re-pot your cosmos plant, as it would self-seed and self-sow into the pot yearly. Put together your cosmos for transplant by giving it a deep watering the day earlier than. It will assist the soil across the roots keep intact and stop the foundation ball from being broken. Dig up your cosmos and transfer it into its new dwelling, sustaining as a lot of the unique root matter as potential. 

Troubleshooting Your Cosmos Plant

Orange C. sulphureus
Orange C. sulphureus. Supply: Mauricio Mercadante

Though they’re comparatively simple to look after, there are some pest and illness points that may have an effect on cosmos. Learn on to learn to determine and deal with these points. 

Rising Issues

Most rising issues with cosmos crops seem as an absence of beautiful flowers. When you discover that your cosmos isn’t flowering, then there are two probably suspects: over-fertilization and/or an absence of daylight. Cosmos want full daylight with a purpose to produce flowers. In case your plant just isn’t producing, you might wish to think about the planting location and assess whether or not or not it may be moved to an space that receives extra daylight. 

Cosmos crops additionally favor lean soil moderately than wealthy soil. This implies the addition of fertilizers can truly trigger extra hurt than good. That is very true when you’ve utilized a nitrogen-heavy fertilizer that may encourage extra foliage on the expense of manufacturing flowers. This may be one other trigger for fewer flowers.  


Some pests, like aphids, flea beetles, and thrips feed on cosmos crops, however they’re usually simple to manage with a powerful spray of water or insecticidal cleaning soap. These bugs all have the same look as small white or greenish bugs that seem in teams, often on the undersides of foliage. 

In a extra superior aphid infestation, neem oil is usually a helpful therapy. To assist forestall and management aphid infestations, you might think about attracting helpful predatory bugs to your gardens, like ladybugs and predatory wasps. Ladybugs will fortunately feast on aphids and make quick work of any potential infestations. These good bugs could be interested in your backyard by planting loads of flowering and aromatic crops corresponding to mint, dill, marigolds, candy alyssum, yarrow, and many others.


Being within the Asteraceae household implies that cosmos flowers are liable to Aster yellows illness. Contaminated crops have yellow stems, stunted progress, and small malformed flowers. The insect aster leafhopper can carry the pathogen. 

As soon as a plant has been contaminated, there isn’t any option to treatment it, and it’s greatest to take away the contaminated plant to stop the unfold to close by wholesome crops. Leafhoppers favor to overwinter in perennial weeds corresponding to thistles and dandelions. When you’ve got leafhopper issues, then eradicating these perennial weeds can cut back their habitat. They will also be managed with pesticides. 

Powdery mildew seems as a white flour-like powder on the leaves. To forestall powdery mildew points, keep away from overhead watering and at all times backside water your crops. Neem oil may additionally be sprayed as a preventative measure to cut back the colonization of spores on foliage. 

In superior circumstances of mildew, it could be greatest to take away and destroy contaminated plant materials to stop it from spreading to close by wholesome crops. After eradicating contaminated materials, spray neem oil or a liquid copper fungicide onto the rest of the plant and close by crops to cut back the chance of additional unfold. 

The identical goes for bacterial wilt illness. This illness causes the bottom and stems of the cosmos to wilt and brown. There isn’t any treatment for the bacterial pathogen that causes the illness, and affected crops needs to be dug up and disposed of. Forestall the illness through the use of solely disease-free seed and protecting the mattress freed from plant particles. 

Continuously Requested Questions

Cosmos bipinnatus flowers
Cosmos bipinnatus flowers. Supply: nousku

Q: Can cosmos come again yearly?

A: Sure! The cosmos flower simply self-sows and can probably kind a dense patch in a flower mattress the place it would come again yr after yr. Most varieties are annuals and can have to be resown every year, though chocolate cosmos are perennials that develop from tubers and are hardy to USDA zone 7. 

Q: Is cosmos full solar or shade?

A: Cosmos favor full solar however can tolerate and even profit from partial shade in areas with excessive warmth or prolonged intervals of scorching climate. 

Q: The place do cosmos develop greatest?

A: The cosmos flower grows greatest in a sunny spot with well-draining soil. 

Q: What do I do with my cosmos after flowering?

A: They make glorious reduce flowers! They are often reduce and introduced inside for a good looking bouquet. In any other case, reduce them again because the blooms fade, and also you’ll be rewarded with much more cosmos flowers. 

Q: How lengthy do cosmos crops final?

A: Reduce flowers will final for 7-10 days. Cosmos crops will proceed to bloom with common deadheading till the primary frost. 

Q: Do cosmos develop effectively in pots?

A: Sure, they’ll develop effectively in pots if supplied with the suitable drainage. 

Q: How lengthy does cosmos bloom?

A: Cosmos will start blooming in early summer time, and with common deadheading, they are going to proceed to bloom till the primary frost. 

Q: Why are my cosmos so tall?

A: Cosmos, basically, will develop to be a number of ft tall, however sure taller varieties can develop as much as 6ft tall! If rising a taller selection, it’s greatest to plant them in an space of your backyard the place they received’t shade out shorter crops. 

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