Zinnia is an annual herb. The stems are erect, 30~100 cm tall, hispid or hirsute. Leaves broadly ovoid or oblong-elliptic, 5~10 centimeters long, 2.5~5 centimeters wide, base slightly cordate clasping the stem, both surfaces scabrous, densely hispidulous below, base out of three veins.

Heads 5-6.5 cm in diameter, solitary at branch tips, without hollow fertile peduncle. Involucre broadly campanulate; involucral bracts multilayered, broadly ovate or ovate-elliptic, outer layer ca. 5 mm, inner layer ca. 10 mm, margin black. Stipules with extended appendages at upper end; appendages purplish-red, fimbriate-triangular. Ligule crimson, rose, violet or white, ligule obovoid, apex 2-3-toothed or entire, pubescent above, villous below. Tubular flowers yellow or orange, 7-8 mm long, apex lobes ovate-lanceolate, densely yellow-brown velutinous above.

Female flower achenes obovoid, 6-7 mm long, 4-5 mm wide, flattened, with 1 rib in the ventral center and on each side of the margin, truncate at the tip, narrowed at the base, and densely hairy; tubular-flowered achenes obovate-cuneate, 7-8 mm long, 3.5-4 mm wide, extremely compressed, sparsely hairy, and short-toothed at the tip.
There are monopetalous, bipetalous, curly-leaved, crumpled-leaved, and variously colored horticultural varieties. Flowering period June to September, fruiting period July to October.

PLANTING

Annual 

Germination: 7-10 days

Germination Temperature: Optimum soil temperatures 75-85ºF.

Seed Planting Depth: Lightly cover

Starting Indoors: Start indoors 4-6 weeks before the last frost. Provide 70-85ºF. soil temperature. Transplant after last frost, space 8-12" apart. 

Sowing Outdoors: After the last frost when soil is over 70ºF. Sow a few seeds every 8-12". Thin to the most robust seedlings. For shorter growing seasons they will bloom toward the end of the summer. We like to start seeds both ways, indoors and outdoors for an earlier and longer blooming. 

Growth Habit: Upright and branching

Height and Width: 15-20"

Spacing: 8-12" apart

Light Needs:  Full sun, part shade in hot climates

Soil Needs:  Loose, rich, well-drained

Approximate days to flower from seed: 75-80 days

Uses: Cut flowers, flower beds, containers, attracts butterflies and beneficials. 

Care: Amend soil with compost before sowing or transplanting. Water seedlings regularly until established. Water well during dry spells. Pinch back plants when they are young for a bushier growth habit. Harvest flowers often for bouquets or deadhead to encourage more blooms.