Helianthus decapetalus (thin-leaf sunflower) — Perennial forb

Overview

Helianthus decapetalus is a perennial forb in the genus Helianthus, part of the Asteraceae family. It typically grows around 1.2 m tall. Helianthus decapetalus grows best in full sun, and tolerates most soils. Its UK hardiness is rated H7. It is native to Georgia, Tennessee, Maine, Massachusetts, Missouri, Pennsylvania, South Carolina and District of Columbia.

About the genus

Helianthus is a genus comprising around 50 species of annual and perennial flowering plants in the daisy family Asteraceae commonly known as sunflowers. The species of Helianthus are native to North America. The best-known species is the common sunflower.

Wikipedia contributors, "Helianthus", CC BY-SA 4.0 — Helianthus

In the garden

Helianthus decapetalus is a perennial forb in the family Asteraceae, native to parts of the eastern and central United States such as Georgia, Tennessee and Maine. Plants reach roughly 1.2 m and carry yellow composite blooms through the late summer and early autumn, providing colour from July to October. Its flowering season makes it useful for extending the season in mixed schemes. Give it full sun and a soil that remains moist but drains freely; it tolerates sandy, loamy or clay substrates provided they are not waterlogged. In UK terms the species is H7 (fully hardy) and also aligns with USDA zones 2–8, so it will cope with a wide range of winters and summers where soils are suitable. Positioning where roots can access consistent moisture without sitting in standing water will keep plants flowering well. Use thin-leaf sunflower at the rear of a mixed border, in informal meadowing or on a sunny bank where its 1.2 m height won’t obscure lower plants. Because it holds its flowering later in the season, place it where the summer-to-autumn display can be seen from paths or seating rather than behind tall shrubs that hide its July–October blooms.

Growing conditions

Best soil and position for Helianthus

Sunlight: Full sun
Soil type: Sandy, Loamy, Clay
Soil moisture: Moist but well-drained
UK hardiness: H7

Plant details

Helianthus decapetalus size, habit and characteristics

Plant type: Perennial forb
Height: 1.2 m
Native to: Georgia, Tennessee, Maine, Massachusetts, Missouri, Pennsylvania, South Carolina, District of Columbia

Care notes

Pruning and caring for Helianthus decapetalus

Propagation: Seed

Frequently asked questions

Where is the best place to plant Helianthus decapetalus?

Helianthus decapetalus prefers full sun.

What soil does Helianthus decapetalus need?

Helianthus decapetalus is adaptable and grows happily in most soil types, including sandy, loamy and clay. Aim for soil that stays moist but well-drained.

How big does Helianthus decapetalus grow?

Helianthus decapetalus reaches a height of 1.2 m.

Is Helianthus decapetalus hardy in the UK?

Helianthus decapetalus has an RHS hardiness rating of H7, meaning it is fully hardy throughout the UK, tolerating temperatures below -20°C.