Do Cosmos Make Good Cut Flowers?

white, pink, yellow cosmos in vase

Cut flowers can add beauty and life to any garden or home, and cosmos are a great option for those looking for an easy-to-grow flower that will bloom for months. These flowers come in many colors, so you can find the perfect one to match your style.

They also don’t require much fuss, making them an excellent option for beginner cut flower gardeners.

Cosmos make excellent cut flowers that last up to a week in the vase. Cut the stems when the buds are just starting to open for the longest vase life. The blooms are beautiful enough to stand on their own in a bouquet, or they make an excellent filler flower in mixed arrangements.

Keep reading to learn more about cosmos as cut flowers. You’ll even find an easy recipe for flower food to keep your cosmos fresh in the vase for as long as possible.

Can you put cosmos in a vase?

Cosmos’ multi-colored blooms and feathery foliage make them ideal flowers for displaying in vases. While a simple bouquet of cosmos makes a stunning centerpiece, combining cosmos blooms and foliage with other flowers like zinnias and snapdragons makes for a charming design.

bouquet of cosmos, black eyed susans, calendula, mint
Double click cosmos are gorgeous in the vase.

When you put cosmos in a vase, remember to strip the lower stems of any leaves. If you leave the leaves on the stem, they will rot in the water, introducing bacteria to the plant and shortening the life of your arrangement.

Do cosmos last as cut flowers? 

Cosmos flowers cut for a floral arrangement can last seven to ten days. Individual flowers may only last a shorter amount of time, but cosmos boast multiple blooms on a single stem that open up over a week or more, increasing the overall life of the arrangement.

To keep your cosmos blooms lasting as long as possible once they’re in the vase, start by giving them a fresh cut. Using a sharp knife or garden shears, cut the stem at an angle about an inch from the bottom. The angle allows the stem to absorb water more efficiently and prevents the end from becoming mushy.

Next, immediately place your cosmos in a vase or container of lukewarm water. You can add a floral preservative to the water to help keep the flowers fresh, but this isn’t required. Just make sure to change the water every few days and recut the stems to keep them fresh as long as possible.

With just a little care, your cosmos flowers will make beautiful bouquets and arrangements that will brighten up any room.

Will cosmos buds bloom after cutting?

Cosmos bloom after cutting, and to ensure a longer-lasting bouquet, it is recommended to cut cosmos when the buds are just beginning to open. Cosmos buds will open up over several days and last for a week or longer.

Add a floral preservative to the water to encourage cosmos to bloom after being cut. The preservative is also known as flower food and provides the energy the flowers need to open that they would otherwise get from the plant.

You can buy ready-made flower food such as Chrysal or make your own with what you probably already have in your kitchen. Here’s a quick recipe:

  • 1 quart of lukewarm water (buy distilled water if you have a water softener)
  • 1 tablespoon sugar
  • 1 tablespoon lemon juice or apple cider vinegar
  • A drop of bleach

The sugar will provide the flowers with the energy they need to open, while the lemon juice or vinegar will help slow down the wilting process. Adding a drop of bleach to the water will help to prevent bacteria from growing in the vase.

How to grow your own cosmos for floral arrangements?

Easy to grow and productive bloomers, cosmos are great flowers for beginning gardeners to grow. Coming in dwarf and standard sizes, they are popular with pollinators and make excellent, long-lasting floral arrangements.

Cosmos can be started indoors from seed, or they can be directly sown in your garden after all danger of frost has passed. 

To plant your seeds, prep your garden bed by removing old plants or weeds and scratching the soil surface with a rake. Scatter your cosmos seeds and lightly cover them with ¼” of soil. 

Keep your beds well-watered until your cosmos germinate, which will take approximately one week.

cosmos seedlings in plastic pots

Because most cosmos have a bushy growth habit, thin your cosmos to approximately 12 inches apart to prevent plants from being overcrowded. 

Cosmos do not need to be fertilized throughout the growing season as too rich soil can promote excessive leaf growth with fewer blooms. Read more about that in this article, 4 Reasons Your Cosmos Aren’t Flowering (And how to fix it).

When your cosmos begin to bloom, cut flowers frequently and deadhead old spent blossoms to encourage continuous production and keep your plants looking tidier. 

Standard-sized cosmos can grow quite large at up to five feet tall. The plants may require staking as the growing season progresses to prevent them from flopping over.

If you need smaller varieties to grow in pots or just due to limited space, check out this article for a height comparison of some popular cosmos varieties: How Tall Do Cosmos Grow? (It depends on the variety).

Cosmos bloom once the summer days get longer and continue blooming for many months, right up to the first fall frost. Although cosmos are annuals, they are efficient self-seeders, so be sure to remove old flower heads if you do not want your cosmos to seed themselves. 

How do you harvest cosmos for cut flowers?

To harvest cosmos as cut flowers, look for stems with a mix of flowers that have just opened and unopened buds that are developing color. Cut the stem at least a foot long with a sharp, clean knife or gardening shears, carefully remove lower branches or foliage as needed, and place in water immediately.

Cosmos will produce more blooms for harvest the more you cut them because they are a cut and come again flower. Whenever you harvest a batch of stems, the plant responds by producing more stems and more buds, so don’t be shy about cutting flowers.

Although it can feel like you’re taking too much from the plant, cosmos are quite tough and can handle a lot of harvesting.

As always, it’s best to cut your flowers in the morning when they are fully hydrated after a night’s rest. Being fully hydrated will help your flowers to last longer. For more harvesting tops, check out this article, When To Cut Flowers: The Right Time To Harvest Blooms.

If you are looking for a long-lasting cut flower for your vase, cosmos should be at the top of your list!

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