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Helianthus annuus 'Sonja' Sonja Sunflower

Edward F. Gilman


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
Figure 2. Sheded area represents potential planting range.
Figure 2.  Sheded area represents potential planting range.


Height: 2 to 6 feet
Spread: 1 to 2 feet
Plant habit: upright
Plant density: open
Growth rate: fast
Texture: coarse


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 color: yellow
Flower charcteristic: showy


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


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


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.

Publication #FPS-244

Date: 6/3/2015

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About this Publication

This document is FPS-244, one of a series of the Environmental Horticulture Department, UF/IFAS Extension. Original publication date October 1999. Visit the EDIS website at for the currently supported version of this publication.

About the Authors

Edward F. Gilman, professor, Environmental Horticulture Department, UF/IFAS Extension, Gainesville, FL 32611.


  • Gail Hansen de Chapman