Introduction

Sunflower is a short-lived annual with large, striking flowers (Figure 1). Large types grow to 12 feet tall, but many garden cultivars are 4 to 5 feet tall. The familiar flowers have yellowish petals with a brown central disc, and grow to 6 to 12 inches across. Plants are seeded in late winter to early spring in Florida, produce lovely flowers in mid-spring, and decline quickly in the heat by late spring to early-summer. Plants in Florida installed in the fall can produce a nice flower display for several weeks in the fall.

General Information

Scientific name: Helianthus annuus 'Sonja'

Pronunciation: heel-ee-ANTH-us AN-yoo-us

Common name(s): 'Sonja' sunflower

Family: Compositae

Plant type: annual

USDA hardiness zones: all zones (Figure 2)

Planting month for zone 7: Apr; May

Planting month for zone 8: Mar; Apr

Planting month for zone 9: Feb; Mar

Planting month for zone 10 and 11: Dec; Jan; Feb

Origin: native to North America

Uses: specimen; accent; mass planting

Availablity: somewhat available, may have to go out of the region to find the plant

Description

Height: 2 to 6 feet

Spread: 1 to 2 feet

Plant habit: upright

Plant density: open

Growth rate: fast

Texture: coarse

Foliage

Leaf arrangement: alternate

Leaf type: simple

Leaf margin: dentate

Leaf shape: ovate

Leaf venation: pinnate

Leaf type and persistence: not applicable

Leaf blade length: 8 to 12 inches

Leaf color: green

Fall color: not applicable

Fall characteristic: not applicable

Flower

Flower color: yellow

Flower charcteristic: showy

Fruit

Fruit shape: oval

Fruit length: less than .5 inch

Fruit cover: dry or hard

Fruit color: black

Fruit characteristic: suited for human consumption; attracts birds

Trunk and Branches

Trunk/bark/branches: not applicable

Current year stem/twig color: green

Current year stem/twig thickness: very thick

Culture

Light requirement: plant grows in full sun

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

Drought tolerance: moderate

Soil salt tolerances: unknown

Plant spacing: 18 to 24 inches

Other

Roots: not applicable

Winter interest: not applicable

Outstanding plant: not particularly outstanding

Invasive potential: may self-seed each year

Pest resistance: very sensitive to one or more pests or diseases which can affect plant health or aesthetics

Use and Management

The cultivar 'Valentine' has good uniformity and flowers well in Florida. It has a better overall appearance than either 'Floristan' or 'Hallo'. 'Floristan' has mahogany and light-yellow bicolored flowers; 'Hallo' has bright golden flowers; 'Valentine' has lemon-yellow flowers. 'Sonja' has big, yellow-orange flowers.

Pest and Diseases

'Valentine' is host to heavy infestations of sweet potato whitefly. 'Big Smile' had no infestation in trials conducted central Florida. Leaf spots can cause severe leaf necrosis.