Introduction

The large, smooth, dark green leaves of this tropical evergreen have light purple undersides and are spirally arranged around stems, forming attractive, arching clumps arising from underground rootstocks (Figure 1). Plants reach to about two feet tall, with the tallest stems falling over and lying on the ground. Beautiful, 1.5-inch-diameter, orange flowers are produced in the warm months, appearing on cone-like heads at the tips of branches. They are especially showy and will stimulate compliments from visitors to your garden.

General Information

Scientific name: Costus igneus

Pronunciation: KOS-tus IG-nee-us

Common name(s): spiral flag, fiery costus

Family: Costaceae

Plant type: perennial

USDA hardiness zones: 9B through 11 (Figure 2)

Planting month for zone 9: year round

Planting month for zone 10 and 11: year round

Origin: not native to North America

Uses: specimen; container or above-ground planter; mass planting; cascading down a wall; accent

Availability: grown in small quantities by a small number of nurseries

Description

Height: 2 to 4 feet

Spread: 2 to 4 feet

Plant habit: upright; spreading

Plant density: open

Growth rate: moderate

Texture: coarse

Foliage

Leaf arrangement: alternate

Leaf type: simple

Leaf margin: entire

Leaf shape: oblong

Leaf venation: parallel

Leaf type and persistence: evergreen

Leaf blade length: 4 to 8 inches

Leaf color: green

Fall color: no fall color change

Fall characteristic: not showy

Flower

Flower color: orange

Flower characteristic: summer flowering; fall flowering

Fruit

Fruit shape: unknown

Fruit length: less than .5 inch

Fruit cover: dry or hard

Fruit color: green

Fruit characteristic: inconspicuous and not showy

Trunk and Branches

Trunk/bark/branches: typically multi-trunked or clumping stems

Current year stem/twig color: green

Current year stem/twig thickness: very thick

Culture

Light requirement: plant grows in part shade/part sun

Soil tolerances: occasionally wet; slightly alkaline; clay; sand; acidic; loam

Drought tolerance: moderate

Soil salt tolerances: poor

Plant spacing: 18 to 24 inches

Other

Roots: usually not a problem

Winter interest: plant has winter interest due to unusual form, nice persistent fruits, showy winter trunk, or winter flowers

Outstanding plant: plant has outstanding ornamental features and could be planted more

Invasive potential: not known to be invasive

Pest resistance: long-term health usually not affected by pests

Use and Management

Growing in either full sun or partial shade, spiral flag needs fertile soil and ample moisture and is often planted near water. It makes a nice accent plant in a shrub border, where the orange flowers will contrast the greens of the shrub border. Planted on two to three foot centers, it acts as a tall ground cover and can brighten a partially shaded location.

Propagation is by division of the clumps, cuttings, or by separating the offsets or plantlets that form below the flower heads.

Pests and Diseases

Mites and nematodes can be a problem, especially on light, sandy soil.

No diseases are of major concern.