Plant guide · October birth flower
Cosmos
Light, airy flowers on tall, feathery stems. Cosmos bloom for months, don't need much care, and are one of the best cut flowers you can grow from a packet of seed.
Warda PatelDreamDrop Gardens, Plano TX6 min readUpdated October 2026
About cosmos
Cosmos are fast-growing summer flowers from Mexico that live for one season. They have simple, daisy-like flowers on long, thin stems.
They look delicate but are tough. They handle dry spells, grow happily in poor soil, and the more you cut them, the more they bloom. Bees and butterflies love them.
Quick facts
- Lives for
- One season (annual)
- Sun
- Full sun, 6+ hours
- Water
- Low once growing
- Height
- 1 to 6 feet
- Plant apart
- 12 to 18 inches
- Blooms
- Early summer to frost
- Seed to flower
- About 2 to 3 months
- Pets
- Generally considered non-toxic
Three kinds you'll see
Garden cosmos
Tall, with feathery leaves and white, pink, magenta or two-toned flowers. The classic cut flower.
Sulphur cosmos
Shorter and bushier, in yellow, orange and red. Handles extra heat.
Chocolate cosmos
Velvety dark red flowers that smell like chocolate. Comes back each year in warmer zones (7–10).
How to care for them
When they bloom
From early summer until frost. Cutting flowers or pinching off dead ones keeps them coming.
- January: not in season
- February: not in season
- March: not in season
- April: not in season
- May: not in season
- June: in flower
- July: in flower
- August: in flower
- September: best month
- October: best month
- November: in flower
- December: not in season
- Sun
- Full sun. In shade the stems flop over and you get fewer flowers.
- Water
- Water young plants regularly. Once they're growing well, they only need a deep watering in long dry spells.
- Soil
- Poor to average soil that drains well. Rich soil and fertilizer make tall, floppy plants with few flowers.
- Cold and frost
- Frost kills them. Sow after your last frost; a hard frost in fall ends the season. Only chocolate cosmos comes back, in zones 7–10.
- Heat
- Handles heat well. Sulphur cosmos is the best choice for very hot summers.
- Pinching
- When plants are about 12 inches tall, pinch off the top. You'll get bushier plants with more flowers.
- Support
- Tall kinds can fall over in wind. Give them a stake or plant them close to neighbors they can lean on.
- Deadheading
- Snip off dead flowers to keep blooms coming, or leave a few so they drop seed for next year.
Are they good in a vase?
Yes, they're a favorite. Long stems, loose and airy shapes, and the plant makes more flowers the more you cut.
- How long they last
- About 5 to 7 days in a vase.
- When to cut
- When the petals are just starting to open from the bud.
- Keep them fresh
- Cut in the cool morning, put the stems straight into water, and change the water often.
- Pairs well with
- Marigolds, zinnias, snapdragons, dahlias and grasses.
Can you dry or press them?
Cosmos are one of the best flowers for pressing. The thin, flat petals press quickly and keep their color.
- PressingGood
- Press single flowers in a heavy book or flower press. Ready in about 1–2 weeks.
- Hang to drySometimes
- The petals are thin and tend to shrivel. Fine for a rustic look, not for crisp flowers.
- Silica gelGood
- The best way to dry whole flowers and keep their shape.
Colors they come in
From pure white and soft pink to deep magenta, plus the warm yellows and oranges of sulphur cosmos.
- Whitee.g. 'Purity'
- Soft pinkGarden cosmos
- Pink and roseGarden cosmos
- Magenta and crimsone.g. 'Rubenza'
- Yellow and orangeSulphur cosmos
- ChocolateChocolate cosmos
Where they come from
Cosmos traveled from the wild hills of Mexico to mission gardens, royal gardens, and finally cottage gardens around the world.
Wild in Mexico
Cosmos grow wild in Mexico and the southwestern US.
Mission gardens
Spanish priests grew them and named them after the Greek word kosmos, meaning 'harmony', because the petals are so evenly spaced.
1600s–1700s: to Europe
Seeds reached Spain, then the royal gardens of France, and England by 1789.
Mid-1800s: to America
Cosmos arrived in American gardens and became a cottage-garden favorite.
The best way to plant them
Cosmos are almost always best grown from seed, but young plants are handy when you want quick color.
- Our pick
From seed
Easy · Flowers in about 2–3 months · Cheapest
The seeds are big and easy to handle, and they sprout in about a week. Cosmos often drop seed and come back on their own next year.
- Sow outside after your last frost, about ¼ inch deep, in full sun.
- Keep the soil damp until sprouts appear (7–10 days).
- Thin them out to 12–18 inches apart. Pinch the tops when they're 12 inches tall.
From young plants (liners)
Easy · Flowers in 4–6 weeks · Mid-price
Liners are small starter plants grown in trays. They give you a head start if your summer is short, and a neat, even bed.
- Plant after your last frost. Don't bury the stem deeper than it sat in the tray.
- Water well and keep damp for the first week or two.
- Pinch the tops once they're settled in.
From a grown plant
Easiest · Flowers right away · Highest price
Instant flowers for pots and gifts. Tall cosmos don't love being moved, so pick shorter kinds.
- Pick plants with buds, not just open flowers.
- Plant in full sun and water deeply.
- Stake tall plants right away.
Questions people ask us
Do cosmos come back every year?
Most are annuals that live one season, but they drop seed easily, so new plants often appear next spring. Chocolate cosmos comes back each year in zones 7–10.
Why are my cosmos tall with no flowers?
Usually too much fertilizer or soil that's too rich. Stop feeding them and pinch off the tops.
Are cosmos safe for pets?
Garden cosmos is generally considered non-toxic to cats and dogs. Check with your vet if a pet eats a lot of any plant.
Do cosmos attract bees and butterflies?
Yes. Their open flowers make it easy for bees, butterflies and other pollinators to feed.
Can I grow cosmos in pots?
Yes. Choose short kinds, like the Sonata series, and use a pot at least 12 inches wide.