Ornamental · Asteraceae
Sunflower
Helianthus annuus
Give it full sun and a sheltered spot, and the sunflower stands tall from summer into fall.
Full sun
70–100 days
USDA 2–11
2–10 ft · 0.5–3 m
Overview
Few plants read summer like a sunflower. It belongs to the daisy family and grows wild across much of North America, where it climbs fast from a single seed into a plant that can top 10 feet (3 m) in one season. Set it in full sun and stand back.
The range is wide. Some are towering single-stem giants bred for one massive head and a heavy crop of seed, while others branch low and carry dozens of smaller blooms for weeks. Cut-flower growers reach for the pollenless types that stay clean in a vase, and there are dwarf cultivars no taller than a window box.
Sunflowers are about as forgiving as a flower gets. They ask for sun, warm soil, and a little room, and they handle drought once they're rooted. The main thing to plan for is their size, since the tallest types need a sheltered spot and a stake before the heads grow heavy.
Care
The short version: full sun, deep and well-drained soil of average fertility, and steady water while seedlings establish and again around bloom, easing off once the plants are settled and drought tolerant.
Light
Sunflowers want full sun, plain and simple. Give them the brightest, most open spot you have, and they reward it with strong stems and big heads. Shade leaves you with weak, leaning plants and far fewer flowers.
Water
Keep the soil moist while the seeds germinate and the seedlings find their feet. Then water deeply and regularly for about 20 days before and after flowering, when the heavy heads need it most. Once they're established, sunflowers are notably drought tolerant and need very little from you.
Soil
Plant in deep, loose, well-drained soil of average fertility. The long taproot needs room to drive down, so break up any hardpan before sowing. Rich ground isn't required, and the plants do fine in ordinary garden soil.
Humidity
Ordinary outdoor air suits sunflowers, so there's no number to hit. Good airflow matters more, since crowded, damp foliage is what invites downy mildew.
Feeding
Sunflowers don't ask for much. Side-dress once with a slow-release all-purpose fertilizer after a few true leaves appear, and leave it there. Go easy on nitrogen, which pushes leafy growth and disease at the expense of blooms.
Pruning
There's little to do here beyond deadheading spent flowers to keep a branching type blooming longer. Cut out any damaged or diseased growth as you spot it.
Size & spacing
Plants range from 18 inches to 1.5 to 10 feet (0.5 to 3 m) tall depending on the type, and spread 1.5 to 3 feet (46 to 91 cm). Pick a cultivar that fits the space and give each one room so air moves freely through the bed.
When to plant
Sunflowers run on warmth and won't tolerate frost. Sow the seeds straight in the ground after the last spring frost, once the soil has reached at least 60°F (16°C), and the plants bloom from mid summer into fall. Harvest the seed heads in early fall, when the backs turn yellow-brown and nod down.
Northern hemisphere
Southern hemisphere
Typical months for a temperate climate: start earlier in warm zones, later where spring frosts linger.
- Sow: Usually unnecessary; sunflowers resent transplanting, so indoor starting is generally not recommended
- Plant: After the last spring frost, once soil has warmed to at least 60°F (16°C)
- Harvest: Blooms mid to late summer into fall; harvest seed heads in early fall when the back of the head turns from green to yellow-brown and nods downward
Hardiness
USDA hardiness zones: 2–11
Temperature: down to -46°C
Troubleshooting
Most sunflower trouble lands on the leaves, the flower heads, or the tall stems. Catch it early and a small problem stays small. Match what you see below, then act while it still helps.
Webbing and chewed seeds inside the flower head
Caterpillars, often sunflower moth larvae, burrow into the head and feed on the buds, petals, and forming seeds. Open a suspect head and you'll find tunneling, webbing, and dark frass among the seeds. Pick them out where you can, cut away badly infested heads, and time a labeled control for early flowering if the damage spreads.
Fix:
- Handpick caterpillars where practical
- Remove and destroy heavily infested heads
- Apply a labeled biological or insecticidal control at early flowering if needed
Yellow blotches on top of the leaves with gray fuzz underneath
This is downy mildew, a fungal trouble that flares in cool, wet spells and shows as pale blotches up top with downy gray growth on the underside. It stunts and twists new growth as it spreads. Pull and destroy affected plants, open up the spacing for airflow, and keep water off the leaves.
Fix:
- Remove and destroy affected plants and debris
- Improve air circulation and avoid overhead watering
- Plant resistant cultivars where available
Seeds stripped from the head before you can harvest
Birds find ripening sunflower seeds long before you do and strip the heads as they fill. Slip a mesh bag or row cover over the heads once the seeds start to plump up. Spinners, reflective tape, or an owl decoy buy some time, and you can always cut nearly ripe heads to finish drying indoors.
Fix:
- Cover maturing heads with mesh or row cover
- Use scare devices such as spinners, reflective tape, or owl decoys
- Cut and dry nearly mature heads indoors to finish ripening
Tall plants leaning or snapped after wind and rain
Giant single-stem types carry such heavy heads that they lodge, leaning or snapping when wind and rain hit. Stake the tall cultivars early, before the heads fill out. Deep, even watering builds a stronger root system, and a sheltered spot keeps the worst gusts off them.
Fix:
- Stake tall and giant cultivars
- Provide deep, even watering to encourage strong rooting
- Site plants where they are sheltered from strong wind
Sticky leaves and clusters of tiny insects on the stems
These are aphids, soft little insects that gather on stems and leaf undersides and leave a sticky honeydew behind. Knock them off with a hard jet of water and let lady beetles and lacewings finish the job. Reach for insecticidal soap only when the colonies get out of hand.
Fix:
- Dislodge aphids with a strong jet of water
- Encourage natural predators such as lady beetles and lacewings
- Apply insecticidal soap if populations are heavy
Toxicity
Good news for households with pets: the sunflower is safe top to bottom. The ASPCA lists it as non-toxic to cats, dogs, and horses, and the seeds are a familiar snack for people and birds alike. A curious nibble on a leaf or petal is nothing to worry about.
Safe for
People · Cats · Dogs · Horses · Rabbits · Livestock · Birds
Cats None
Sunflowers are safe around cats. A curious nibble on a leaf or petal won't cause any real harm.
Dogs None
Dogs can be near sunflowers without worry, and the seeds are a wholesome snack in moderation.
Horses None
Horses graze around sunflowers safely. ASPCA lists the plant as non-toxic to them.
Rabbits Safe
Rabbits can browse the leaves and flowers with no ill effect, so a stray stem is nothing to fret over.
Livestock Safe
Cattle, goats, and sheep do fine around sunflowers, and the seed is even used as a feed ingredient.
Birds Safe
Birds love sunflower seed and come to no harm from it. The ripe heads are a natural feeder for them.
People Safe
The seeds are a popular snack, raw or roasted, and the whole plant is safe for people.
Varieties
Thousands of sunflowers exist, but a few types cover most gardens, from towering giants to vase-ready cut flowers. These are the ones worth knowing by name.
Mammoth (Russian Giant)
This is the towering single-stem giant grown for its huge heads and heavy crop of edible seed.
Autumn Beauty
A branching type that throws many smaller blooms in warm autumn shades over a long season.
ProCut and Sunrich series
These single-stem pollenless sunflowers are bred for clean, long-lasting cut flowers.
Teddy Bear
A dwarf with fluffy double blooms that fits small spaces and grows happily in containers.
How to propagate
Sunflowers come from seed and nothing else, which makes them one of the simplest plants to grow from scratch.
SeedEasy
Direct-sow after the last spring frost once soil has warmed to at least 60°F (16°C) · Germinates in about 7 to 10 days
Start sunflowers straight in the ground after your last spring frost, once the soil has warmed to at least 60°F (16°C). Tuck the seeds 1 to 2 inches deep and they push up in about 7 to 10 days. They resent being moved, so skip the indoor pots and sow them right where you want them to stand.
Myths
Mature sunflowers turn their heads to follow the sun across the sky all day.
Only young, still-growing plants track the sun from east to west and swing back east overnight. Once the flower head opens at maturity, that movement stops for good. A field of open sunflowers stands facing east, not chasing the sun.