Illustration
Sea Shells
Cosmos bipinnatus 'Sea Shells'
Sea Shells blooms from June through October.
Months here are Northern Hemisphere months; in the Southern Hemisphere, shift them by six months.
Growing Sea Shells
Plant it in full sun. It prefers low water. Expect it to reach about 3.5 ft tall and 1.5 ft wide at maturity, in roughly 1 year (a house reading).
Pets
- Not yet checked for pets.
Lists differ and none is complete. If a pet eats a plant and seems unwell, call a veterinarian or a pet poison helpline.
No toxicity note is on file for Sea Shells. That is not a clearance: check its safety for people and pets before planting.
What was checked
Nine facts were checked against named botanical sources, each recorded beside the sources that carried it: mature height and spread, hardiness zones, sun, water, bloom months and color, the trait tags, and years to mature size, which rests on a recorded house rule where no publisher states one and is marked so. Soil, diseases, pests, toxicity and the plant's own names have not yet been read for this plant, and its trait tags are the ones a feature uses rather than every word a page prints. Each fact above carries its own mark. The planting, spacing and size sections are derived from these checked facts by a fixed rule, not checked separately, and the plant type is the library's own classification.
When to plant Sea Shells
Wait until all danger of frost has passed, then plant out Sea Shells into warm soil; in most zones that means late spring. Planted then, it flowers from June to October.
Month-by-month timing for your zone is on the planting calendar. Derived from the plant's category, zones and bloom months plus typical zone frost dates, not checked separately.
How big does Sea Shells get?
3.5 fttall5 ft 7 inan adult1.5 ftwideSee Sea Shells in a garden plan: the planner shows it in 3D beside everything else you add, growing toward this size over the years.
How far apart to plant Sea Shells
Derived from the mature spread above by a fixed rule, not checked separately: spacing is the spread, center to center.
Space Sea Shells about 1.5 ft apart, center to center, so each plant has room to reach its full width.
Add Sea Shells to a garden plan and the planner draws it at its full width, so you see the spacing before you buy.
Where these facts come from
Sea Shells' height, spread, hardiness zones, sun, water, bloom months and color and trait tags were checked against 8 published sources on October 25, 2026. Each one is linked below with every fact it carried, which can include a fact this page still marks as not yet checked, because a source carrying a value is not the same as the value being held to the standard. Facts not in that list, and the planting, spacing and size sections, are not covered by these sources.
- Chicago Botanic Gardenhardiness zones, sun, water, bloom months and color and trait tags
- harrisseeds.comHarris Seedsheight, spread, bloom months and color and trait tags
- RHSRoyal Horticultural Societyheight, sun, water and bloom months and color
- jparkers.co.ukJ. Parker'sheight, spread and water
- extensiongardener.ces.ncsu.eduNC State Extensionbloom months and color
- NC State Extensionheight and trait tags
- Missouri Botanical Gardensun
- University of Illinois ExtensionIllinois Extensionsun
How the checking works, and what each standard covers, is on the verified plants page.
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Design a garden with this
Drop this plant onto a 3D plan, see how it fills in, and watch your whole garden bloom across the year.