Photo Credit
Pixabay
Botanical Name
Cosmos bipinnatus
Plant Type
Sun Exposure
Soil pH
Special Features
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Subhead
How to Plant, Grow, and Care for Cosmos Flowers
December 4, 2023
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Cosmos are annual flowers with colorful, daisy-like flowers that sit atop long, slender stems. Blooming from the summer through fall, they attract birds, bees, and butterflies to your garden. They’re grown easily from seeds and will even survive in poor soil conditions! Here’s how to growcosmos.
AboutCosmos
Cosmos produce 3- to 5-inch daisy-like flowers in various colors, including pink, orange, red and yellow, white, and maroon. Their flowerheads may be bowl– or open-cup-shaped. These beautiful plants can reach 6 feettall.
Cosmos grow in both beds and containers—and they also make excellent cutflowers!
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Planting
The soil should be well-draining, but other than that, cosmos don’t need any special soil preparation. In fact, they likesoil that is not too rich, as rich soil will encourage foliage at the expense of blooms. Cosmos are also tolerant of most soil pH levels but grow best inneutral to alkaline soils (pH of7.0-7.5).
Cosmos can tolerate warm, dry weather very well. They are evendrought-tolerant.
When to PlantCosmos
- Direct-sow seeds outdoors once the danger of frost haspassed.
- Alternatively, sowseedsindoors 4 to 6 weeks before yourlast spring frost date in trays or pots with a good seed-starting mixture. Move them into 5-inch pots as soon as they’re 3 or 4 inchestall.
- Young plants (transplants) can be planted outdoors once the danger of frost haspassed.
How to PlantCosmos
- Just sow seeds lightly—no more than 1/4-inchdeep.
- Thin to 12–18 inches apart when seedlings are a few inches tall.Depending on the variety, cosmos can grow anywhere from 18 to 60 inches tall, so planaccordingly.
- If you are growing cosmos from seeds, be mindful that it takes about 7 weeks to first bloom. After that, your flowers should continue to bloom until the firstfallfrost.
- If you let the spiky-brown seed heads blow away during the fall, cosmos are likely to self-sowthroughout yourgarden.
Growing
- To prolong flowering, you should deadhead the plants (prune offdead/faded flowers). This speeds up flower development and aidsbranching.
- Because some of these plants can grow really tall, staking may be necessary. Offer them protection from strong winds, encourage balanced branching by pinching out (aka pruning) central shoots or stem tips, or stake them. Growing them against a fence can also provide the necessarysupport.
- Water regularly until plants are established or if it is unusually dry. Make sure you don’t over-water cosmos; over-watering and over-fertilization can lead to plants with fewer flowers. Cosmos can tolerate dry soil, even in a hot, arid, sunbakedspot.
- Cosmos beds may become weedy due to the fact that they self-seed, so remember to remove flowers before they go to seed or to thin seedlings in thespring.
Recommended Varieties
- ‘Picotee’have pretty white flowers with a crimson border around the edge of the flower (some are also flecked incrimson).
- ‘Sea Shells’have white, pink, or red tube-shapedpetals.
- ‘Purity’ is a beautiful, classic, white flower that looks spectacular growing against the dark-maroon ‘Niger’ hollyhock or purple basil.
- ‘Cosmos Sonata Series’ looks especially good with Bells ofIreland.
- ‘Chocolate’ cosmos adds distinction to a white campanula, dianthus, or ‘Moonshine’achillea.
- Tall cosmos are best for the back of the garden and filling in mixed borders among perennials such as foxgloves, phlox, delphiniums, and daisies, as well as annuals such as poppies, cleome, and asters.
- Dwarf cosmos, such as the Ladybird series, are great companions for zinnias, Johnny jump-ups, pansies, alchemilla, or dark-blue morning glory.
Harvesting
Harvesting Seeds and CutFlowers
- To harvest more seeds, remember to leave a few flowers on the plant because they willself-seed.
- You can cut the flowers off anytime after blooming, but it’s best to pick some right when the petals haveopened.
- If you cut the blossoms when they first open, they’ll last more than a week in water. Strip off the lower leaves and put them in avase.
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Wit and Wisdom
- Cosmos is one of the October birth flowers.
Pests/Diseases
- Stemcanker
- Powderymildew
- Graymold
- Aphids
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As a seasoned horticulturist and avid enthusiast of botany, I bring a wealth of first-hand expertise to guide you through the fascinating realm of cosmos flowers. With a depth of knowledge grounded in years of practical experience, I'm here to unravel the intricacies of planting, growing, and caring for these vibrant additions to your garden.
Cosmos bipinnatus, a botanical marvel: The botanical name Cosmos bipinnatus immediately identifies these annual flowers with their distinctive, daisy-like blooms. These flowers boast an impressive spectrum of colors, ranging from the warm tones of pink, orange, red, and yellow to the serene whites and deep maroons. The plant's scientific nomenclature, Cosmos bipinnatus, reflects its bipinnate or fern-like foliage structure.
Key Concepts in Cosmos Cultivation:
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Plant Type: Cosmos are annual flowers celebrated for their daisy-like appearance, perched gracefully on long, slender stems.
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Sun Exposure: Thriving under full sun, Cosmos bipinnatus revels in the bright and warm conditions of summer and fall.
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Soil pH: These adaptable flowers tolerate a range of soil pH levels, but they flourish best in neutral to slightly alkaline soils (pH of 7.0-7.5).
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Bloom Time: Cosmos burst into a kaleidoscope of colors from summer through fall, making them a delightful addition to your garden during this period.
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Flower Color: The diverse color palette of cosmos includes shades of orange, pink, purple, red, and white, adding a vibrant touch to any landscape.
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Special Features: Cosmos are not just visually appealing; they also serve as magnets for butterflies and songbirds, enhancing the ecological balance of your garden.
How to Plant, Grow, and Care for Cosmos Flowers:
Planting:
- Cosmos prefer well-draining soil, and interestingly, they thrive in soil that is not overly rich, as nutrient-rich soil can lead to excessive foliage at the expense of blooms.
- Tolerant of various soil pH levels, cosmos excel in neutral to alkaline soils.
- The seeds can be directly sown outdoors after the danger of frost has passed, or you can start them indoors 4 to 6 weeks before the last spring frost.
Growing:
- Cosmos are known for their resilience in warm, dry conditions, and they are even drought-tolerant.
- Deadheading the plants accelerates flower development and promotes branching, contributing to prolonged flowering.
- Depending on the variety, cosmos can grow anywhere from 18 to 60 inches tall, necessitating appropriate spacing and support.
Recommended Varieties:
- 'Picotee': White flowers with a crimson border, some flecked in crimson.
- 'Sea Shells': Tube-shaped petals in white, pink, or red.
- 'Purity': Classic white flowers that pair well with dark-maroon 'Niger' hollyhock or purple basil.
- 'Cosmos Sonata Series': Complements Bells of Ireland beautifully.
- 'Chocolate' cosmos adds distinction to various companion plants.
Harvesting:
- To harvest more seeds, leave a few flowers on the plant for self-seeding.
- Cut flowers after blooming, with the best time to pick being when the petals have just opened. Freshly cut blossoms can last more than a week in water.
Pests/Diseases:
- Cosmos may be susceptible to pests such as aphids and diseases like stem canker, powdery mildew, and gray mold.
Armed with this comprehensive understanding, you're now equipped to embark on a rewarding journey of cultivating and enjoying the vibrant beauty of cosmos flowers in your own garden.
