Illustration
Swamp Sunflower
Helianthus angustifolius
Also called narrow leaf sunflower
Swamp Sunflower blooms from October through November.
Months here are Northern Hemisphere months; in the Southern Hemisphere, shift them by six months.
Growing Swamp Sunflower
Plant it in full sun. It prefers moderate water. It is hardy in USDA zones 5–9. Expect it to reach about 6 ft tall and 2.5 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 Swamp Sunflower. 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 Swamp Sunflower
Plant Swamp Sunflower in early spring as soon as the soil is workable, or in early fall at least six weeks before your first frost, so roots establish in cool weather. In zone 7, the middle of its hardy zones 5 to 9, spring means March to May and fall means September or October. Once settled, it blooms from October to November.
Month-by-month timing for your zone is on the planting calendar; if you garden near zone 7, the middle of this plant's hardy range, start with zone 7 in March. Derived from the plant's category, zones and bloom months plus typical zone frost dates, not checked separately.
How big does Swamp Sunflower get?
6 fttall5 ft 7 inan adult2.5 ftwideSee Swamp Sunflower 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 Swamp Sunflower
Derived from the mature spread above by a fixed rule, not checked separately: spacing is the spread, center to center.
Space Swamp Sunflower about 2.5 ft apart, center to center, so each plant has room to reach its full width.
Add Swamp Sunflower 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
Swamp Sunflower's height, spread, hardiness zones, sun, water, bloom months and color and trait tags were checked against 9 published sources on October 23, 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.
- NC State ExtensionGardener Plant Toolboxheight, spread, hardiness zones, sun, water, bloom months and color and trait tags
- New Moon Nurseryheight, spread, hardiness zones, water, bloom months and color and trait tags
- ffl-apps.ifas.ufl.eduUniversity of Florida IFAS, Florida Bee Gardensheight, spread, hardiness zones, sun and bloom months and color
- kollarnursery.comKollar Nurseryheight, spread, hardiness zones, sun and water
- Mt. Cuba CenterNative Plant Finderheight, hardiness zones, water and bloom months and color
- RHSRoyal Horticultural Societyheight, sun and bloom months and color
- tnyards.utk.eduUniversity of Tennessee, Tennessee Smart Yardsheight, water and bloom months and color
- University of Wisconsin HorticultureUniversity of Wisconsin-Madison Division of Extension, Wisconsin Horti...height and bloom months and color
- Iowa State University Extensionand Outreach, Yard and Gardenheight
How the checking works, and what each standard covers, is on the verified plants page.
Where it grows wild
Native to 24 states
United States: Alabama, Arkansas, Delaware, Florida, Georgia, Illinois, Indiana, Iowa, Kentucky, Louisiana, Maryland, Mississippi, Missouri, New Jersey, New York, North Carolina, Ohio, Oklahoma, Pennsylvania, South Carolina, Tennessee, Texas, Virginia, West Virginia and 12 more
Recorded growing wild in 438 counties.
Range data from the World Checklist of Vascular Plants, Royal Botanic Gardens, Kew (CC BY 4.0, adapted) and USDA PLANTS. How the native range is credited.
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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.