Perennial sunflower

Perennial sunflower: how do you recognise it?

Habit

Upright, dense clump 1.2–1.5 m tall and about 80 cm wide, with straight, sturdy stems.

Foliage

Rough, dark green, lance-shaped to oval, 10–15 cm long; the lower leaves are opposite.

Flower

Yellow blooms 8–12 cm across with a brown or yellow centre; single or double depending on the cultivar.

Flowering

From July to October; trim faded flowers to extend the display.

Roots

Creeping rhizomes that widen the clump year after year.

Flowering: July–October · Plants: March–May · Pruning: February–March

Why grow it?

• Cheerful yellow flowers from July to October, just when many other perennials have finished.
• Comes back every year without sowing: plant once, enjoy for years.
• Bees and butterflies take nectar and pollen; in autumn birds eat the seeds.
• A good cut flower: the blooms last several days in a vase.
• Fast-growing, it fills a sunny border with height and colour.

Perennial sunflower: where does it grow best?

• Full sun: in shade the stems grow long and floppy and flowering is sparse.
• Ordinary garden soil: sand, loam or clay, acid to chalky. Well-drained soil is best.
• Average moisture; it copes with a dry summer but flowers better with the odd drink.
• Plant in a sheltered spot or stake tall stems: wind can flatten them.
• Space plants 60–80 cm apart and expect a clump that widens a little each year.

Light

Sun

Soil type

Sand, loam or clay

Acidity

Not fussy

Moisture

Normal

Size

1.5 m tall, 0.8 m wide

Hardiness

Hardy (to -30 °C)

Goes well with

• Heliopsis: Another yellow summer bloomer with the same sun and soil needs.
• Rudbeckia: Yellow and brown flowers in the same style, but lower.
• Ornamental grasses: Plumes and stems make a soft, airy backdrop.
• Aster: The purple and blue autumn flowers contrast nicely with yellow.
• Woodland sage: Blue-purple flower spikes for the front of the border.

Perennial sunflower: when and how to plant it?

Plant in March–May.

1. Plant in March, April or May, once the soil is no longer frozen. Container-grown plants can also go in later in the season.
2. Dig a hole at least twice as wide as the root ball and mix in some compost.
3. Set the plant at the same depth as in its pot and firm the soil well.
4. Leave 60–80 cm between plants.
5. Water thoroughly straight away and repeat in dry weather during the first year.
6. Spread a thin layer of compost or fine bark around the base, keeping it off the stems.

Care

Water

Weekly in dry weather during the first year. After that only in long dry spells, thoroughly and at the base.

Feeding

Once in spring, with compost or an organic feed. Too much nitrogen gives long, floppy stems.

Support

In windy spots, put in sturdy canes or a ring in May, before the stems get tall.

Deadheading

Trim faded flowers for more blooms. Leave a few in autumn for the birds.

Dividing

Divide the clump every three years, otherwise the centre goes bare and flowering declines.

Tip: Dividing every three years is the best care: flowering stays generous and the clump does not get too wide. In windy spots, stake tall stems with canes in May.

Perennial sunflower: when to prune it?

Pruning months: February–March.

When: In late February or March, cut the dead stems down to just above the ground.

How:

• Cut all old stems to 5–10 cm above the ground, before the new shoots appear.
• For a more compact plant, cut the shoots back by a third at the end of May. Flowering starts a little later, but the stems are sturdier.
• During flowering, remove faded flowers to stretch the season.

Pruning: when and how · Pruning calendar and basic rules

Propagation

Division

In March–April, lift the clump and split it with a sharp spade into pieces with roots and shoots. Replant at once and water well.

Cuttings

In May–June, take cuttings of 10–15 cm from young shoots and put them in moist cutting compost. They root within a few weeks.

Perennial sunflower: how does it get through the winter?

Hardy to −30 °C.

• Fully hardy to about −30 °C: no protection is needed in Belgian winters.
• The top growth dies back. If you like, leave the seed heads for the birds and cut back only in February or March.
• Winter wet, especially on heavy clay, is more dangerous than frost: make sure the soil drains well.

Diseases and pests

• Slugs: Young shoots are eaten in spring. Pick off slugs, lay a barrier of crushed shells or set a slug trap.
• Powdery mildew: White powder on the leaves, especially in dry weather and when plants are crowded. Water at the base, allow space and divide the clump in good time.
• Flopping stems: In windy or too shady spots. Stake, cut back in May and plant in full sun.
• Aphids: On young tips, especially in dry spells. Rinse off with water; ladybirds will do the rest.

Through the year

• February: Cut old stems down to 5–10 cm above the ground.
• March: Divide and move. Apply compost.
• April: Plant. Watch for slugs on the young shoots.
• May: Plant or stake. Optionally cut back by a third.
• June: Water in dry weather. Buds form.
• July: Flowering begins. Trim faded flowers.
• August: Full bloom. Cut flowers for the vase.
• September: Flowering. Water now and then in dry weather.
• October: Last flowers. Leave seed heads for the birds.
• November: Dormant. Dead stems can stay standing.

Good for wildlife

Bees

Nectar and pollen for honeybees and wild bees.

Butterflies

Nectar for butterflies.

Birds

Berries, seeds or insects as food, or a place to nest.

Did you know?

• The perennial sunflower is a garden hybrid of the annual sunflower and a North American perennial species, so it does not occur in the wild.
• A sunflower is really a flower head: the yellow ‘petals’ are ray florets and the central disc is made up of dozens of tiny tubular florets.
• The name Helianthus comes from the Greek helios (sun) and anthos (flower).