Introduction

There are many varieties of zinnia with widely varying heights and flower colors (Fig. 1). They may be as short as six inches or as tall as three feet. The plants are spaced eight to twelve inches apart and flowers can be any color except for blue. They are tolerant of all but wet soils and need exposure to full sun. Plants producing flowers with high centers surrounded by only one or two rows of petals should be discarded. Tall varieties may be pinched when young to encourage branching. Old flowers are removed to encourage continued flowering.

General Information

Scientific name: Zinnia spp.

Pronunciation: ZIN-nee-uh species

Common name(s): zinnia

Family: Compositae

Plant type: annual

USDA hardiness zones: all zones (Fig. 2)

Planting month for zone 7: Mar; Apr; Sep

Planting month for zone 8: May; Jun

Planting month for zone 9: Apr; Sep; Oct

Planting month for zone 10 and 11: Mar; Sep; Oct

Origin: native to North America

Uses: mass planting; container or above-ground planter; cut flowers; edging

Availability: generally available in many areas within its hardiness range

Description

Height: 1 to 3 feet

Spread: 1 to 2 feet

Plant habit: upright

Plant density: open

Growth rate: fast

Texture: medium

Foliage

Leaf arrangement: opposite/subopposite

Leaf type: simple

Leaf margin: entire

Leaf shape: ovate

Leaf venation: parallel

Leaf type and persistence: not applicable

Leaf blade length: 2 to 4 inches

Leaf color: green

Fall color: not applicable

Fall characteristic: not applicable

Flower

Flower color: yellow; white; pink; salmon; purple; lavender; orange

Flower characteristic: showy

Fruit

Fruit shape: no fruit

Fruit length: no fruit

Fruit cover: no fruit

Fruit color: not applicable

Fruit characteristic: inconspicuous and not showy

Trunk and Branches

Trunk/bark/branches: not applicable

Current year stem/twig color: green

Current year stem/twig thickness: medium

Culture

Light requirement: plant grows in full sun

Soil tolerances: clay; sand; acidic; loam

Drought tolerance: high

Soil salt tolerances: unknown

Plant spacing: 12 to 18 inches

Other

Roots: not applicable

Winter interest: not applicable

Outstanding plant: not particularly outstanding

Invasive potential: not known to be invasive

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

Use and Management

The seeds are usually planted directly into the garden. If planted indoors, the seedlings become spindly, especially if started too early. The seed germinates in one to two weeks at temperatures between 70 and 80°F. In addition to spring, zinnia can be planted from August to September in southern Florida. Dwarf zinnias less than 10 inches tall include the 'Dasher', Dreamland', 'Lollipop', 'Peter Pan' and 'Small World' series, 'Fantastic, 'Short Stuff' and 'Thumbelina'. Intermediate-sized selections grow no more than about 15 inches tall and include the 'Pulcino' series, and the cultivars 'Pumila', 'Rose Pinwheel', and 'Starlight'. The tallest zinnias are in the 'Ruffles' and 'Splendor' series, and the cultivar 'State Fair'.

Pests and Diseases

Aphids suck plant juices and coat the leaves with sticky honeydew.

Four-lined plant bug causes small, round, brown sunken spots on the leaves.

Mites cause the foliage to lose its green color and become bronzed or stippled.

Blight starts as reddish brown spots with graying centers. Dark brown cankers form on the stems and flowers are spotted or completely blighted. The disease is also called alternaria leaf spot.

Powdery mildew is found on zinnia, particularly late in the season. The disease causes a white to grayish powdery growth on the leaves.

Bacterial leaf spot causes reddish brown, angular spots on the leaves and can cause plants to die out by mid-August.