Swamp sunflower
Helianthus angustifolius · Asteraceae
A wall of golden daisies with dark centres in October on stems well above head height. A native of the wet Southeast that runs at the root.
- Size
- 6½ ft tall, 3½ ft wide
- Zones
- 5 to 9
- Light
- Full sun
- Flowers
- Late September to late October
- Pets
- No toxicity recorded
- Job in a bed
- Specimen
A bed built around swamp sunflower
The planner designed this bed around swamp sunflower when this page was made: a 12 × 6 ft (3.7 × 1.8 m) naturalistic planting in zone 6, full sun. It chose the other plants from the 966 that suit those conditions, and says below why swamp sunflower stands where it does.
The plants
- 1 Swamp sunflower × 1, yellow
- 2 Moor grass 'Greenlee' × 9, tan
- 3 Creeping phlox 'Candy Stripe' × 5, pink
- 4 Purple milkweed × 3, purple
- 5 Brown-eyed Susan × 5, yellow
- 6 Hardy gladiolus × 4, pink
- 7 Red spider lily × 7, red
Why this plant
- Nothing here is unique to it. Its leaf, flower shape and colour are all on the plan already. Its case rests on where it stands and when it performs.
Why here
- Anchors a back corner. At 6½ ft it is the tallest plant here, and the tallest close the ends of the bed, where they stand in front of nothing.
- A step in the back row. Next to purple milkweed (3 ft): no two neighbours there are the same height, so the back steps up and down like a skyline.
- One plant, alone. A feature plant is seen as an object, and needs clear ground around it.
Why now
- In flower for five weeks. From late September to late October.
- Closes the season. For its last three weeks nothing else on the plan is in flower.
Planned as a naturalistic planting: low grasses and groundcovers, the matrix, make up 50% of the planted ground. Creeping phlox 'Candy Stripe' and moor grass 'Greenlee' finish the front edge. Cool colours (pink and purple) set against hot ones (yellow and red), with tan to calm things between them. Worth a second look, according to the Design check: heights.
The planner's own design check: 11 Excellent, 5 Good, 1 Needs revision. Its weakest point is height and scale: Heights average about 10 in at the front, 2 ft in the middle and 4 ft at the back. Along the back row the heights step up and down, between 2½ ft and 6½ ft, and no two neighbours are the same height. It flags one thing to watch: Nothing on this plan is highly poisonous or an aggressive spreader.
Open this bed in the planner Change its size, the sun or the style, move plants about, or swap one for another.
Where swamp sunflower goes in a border
At 6½ ft it belongs at the back of a bed. In the planner's ten height classes it is very tall (5 to 6½ ft).
Its job: specimen. A feature plant with a shape of its own. It stands alone with room around it, and repeats only at a distance.
The latest and biggest splash of yellow in the South. Cut it back by half in June to keep it under two metres and upright, and give it room: it spreads.
- A late show for large, moist beds
- Rain gardens
- Screening in autumn
What to plant with swamp sunflower
Plants recorded as good partners for it, and what each pairing does:
- New England aster: purple against yellow, opposite each other on the colour wheel, if you choose those colours, in flower together for three weeks; low enough (4 ft) to stand in front of it; happy in the same moist soil.
- Joe Pye weed 'Gateway': flowers first, late July to mid September, so the spot is never empty; bold leaves against its medium ones; happy in the same moist soil.
- Switchgrass 'Shenandoah': its green leaves are a setting for the flowers, before and after; low enough (4 ft) to stand in front of it.
Questions about swamp sunflower
Does swamp sunflower need sun or shade?
Swamp sunflower grows in full sun (6 or more hours of direct sun a day).
It wants soil that stays evenly moist, of average fertility, and plenty of water. It copes with soil that stays wet.
What zones does swamp sunflower grow in?
USDA zones 5 to 9. It is hardy to zone 5, which means it survives winter nights down to about −10 °F (−23 °C).
Gardening in Canada? Use the USDA zone for your town: Canada's own zone map uses different numbers.
When does swamp sunflower flower in my zone?
In zone 5 it flowers late September to late October. As an autumn flower it keeps much the same dates in every zone: it answers to shortening days and cool nights more than to the warmth of spring.
| Zone 5 | Late September to late October |
|---|---|
| Zone 6 | Late September to late October |
| Zone 7 | Late September to late October |
| Zone 8 | Late September to late October |
| Zone 9 | Late September to late October |
Worked out from Hopkins' bioclimatic law: spring arrives about four days later for each degree of latitude north, and one zone is roughly two degrees. A warm spring or a cold one moves any garden two weeks either way.
How far apart should swamp sunflower be planted?
3 ft (90 cm) apart, from the middle of one plant to the middle of the next. That is a little closer than its full width of 3½ ft (100 cm), so a group knits into one patch.
It grows 6½ ft (200 cm) tall. Give it the full distance from anything taller, or it will lean out towards the light.
How many swamp sunflower plants do I need?
At 3 ft apart, set out in staggered rows:
- 1 to fill 10 square feet (about 1 m²)
- 4 for a single row 10 ft (3 m) long
- 4 to fill a 4 × 8 ft bed on its own
In a mixed border, plant it as one, with clear ground around it: a feature plant is seen as an object, and a group of them is a thicket.
In the bed above, the planner used one in one group.
Is swamp sunflower poisonous to dogs and cats?
No toxicity is recorded for dogs, cats, horses or people, according to NC State Extension and the ASPCA.
"Not toxic" is not "edible": a pet that eats a lot of any plant can be sick.
Do deer eat swamp sunflower?
Mostly not. NC State lists it as resistant to deer. No plant is proof against a hungry deer in a hard winter, but this one is low on the menu.
Will swamp sunflower spread?
It spreads sideways, by runners or roots; the risk of it taking over is moderate. Spreads by underground runners and can crowd its neighbours. Dig out the edges or divide every 2 to 3 years.
What does swamp sunflower look like in winter?
Swamp sunflower dies down, but leave the stems standing: the seed heads stand through the winter, and songbirds eat the seed. Cut them down in early spring, before the new shoots come.
Is swamp sunflower good for bees and butterflies?
Swamp sunflower is visited by pollinators, specialist bees, butterflies and songbirds.
It is a host plant: the caterpillars of silvery checkerspot feed on its leaves. A butterfly can only lay its eggs on its host plants, so these do more for it than any nectar flower.
It is native to the United States.
More Helianthus
- Double perennial sunflower Helianthus x multiflorus 'Flore Pleno'
- Maximilian sunflower Helianthus maximiliani
- Sunflower 'Lemon Queen' Helianthus 'Lemon Queen'
- Willowleaf sunflower 'First Light' Helianthus salicifolius 'First Light'
- Woodland sunflower Helianthus divaricatus
In these guides
- Plants for wet soil and rain gardens
- Salt-tolerant plants for roadsides and coasts
- Deer-resistant perennials for full sun
- Pet-safe plants for a sunny border
- Native perennials for pollinators
- Plants for butterflies
- Plants for bees
- Plants that feed garden birds
- Tall perennials and grasses for the back of a border
- Plants that flower in fall
- Host plants for the silvery checkerspot
Every fact on record
- Type
- Perennial
- Size
- 6½ ft (200 cm) tall, 3½ ft (100 cm) wide
- Plant
- 3 ft (90 cm) apart
- Height class
- Very tall (5 to 6½ ft)
- Place in the bed
- Back
- Flowers
- Late September to late October; daisies; yellow
- Leaves
- Medium texture, herbaceous; dark green
- Shape
- Upright, spreading
- Hardy in
- USDA zones 5 to 9
- Light
- Full sun
- Soil
- Average, evenly moist
- Water
- High
- Feeding
- None needed
- Family
- Asteraceae
- Comes from
- USA
- Attracts
- Pollinators, specialist bees, butterflies, songbirds
- Host plant for
- Silvery checkerspot
- Stands up to
- Deer, salt, wet soil, poor soil
Checked against NC State Extension and ASPCA poison lists. Flowering times are for zone 5: later in colder zones, earlier in warmer ones. Toxicity and spread information is a general gardening guide, not veterinary or medical advice, and invasive status varies by region. If a person or pet eats a plant, contact poison control or a vet. Check your local invasive species list before planting anything with a spread warning.