Zinnia plants are half hardy annuals. They range from 20 to 90 cm (8 to 36 inches) in height.
They bloom from summer through to the first frost.
When in bloom, they carry single or double blooms. The flowers are often pink, purple, red, orange, or white.
Profusion flower (above) and Common Zinnia (below).
They are able to grown in zones 2 through 10, and can be sown out in the garden following the last frost.
Common species of Zinnia grown in the garden include Profusion flower and 'youth and old age'.
Zinnia by Photofarmer.
Zinnia elegans (Elegant Zinnia / Common Zinnia / Youth-and-age), photograph by Forest and Kim Starr; CC.
Full growing Guide available at How to grow Zinnia elegans.
Zinnia angustifolia (Narrowleaf Zinnia), photograph by Eric Savage; CC.
Visit How to grow Zinnia angustifolia for an in-depth growing guide.
Zinnia grandiflora (Rocky Mountains Zinnia / Plains Zinnia), photograph by Patrick Alexander; CC.
Zinnia acerosa (Desert Zinnia / Wild Zinnia / Spinyleaf zinnia), photograph by Patrick Alexander; CC.
Zinnia haageana (Mexican Zinnia), picture by 阿橋 HQ; CC.
Zinnia bicolor Macarenia (Macarenia Zinnia), photograph by Swallowtail Garden Seeds; CC.
If growing Zinnia from seed, then sow outdoors following the last frost of spring. Lightly cover the seed once sown.
Plants should be spaced at 15 to 20 cm (6 to 8 inches; small), 25 to 30 cm (10 to 12 inches; medium), or 45 cm (18 inches; large Zinnia species) apart.
Ideally grow Zinnia plants in a sunny area of the garden that gets an afternoon shade. The plants are able to grow in most soils of pH 6 to 7. The soil should be enriched with manure for best results.
In cold areas, it may be a good idea to start off Zinnia seedlings indoors first. Do so about seven weeks in advance of transplanting.
It should take about one to three weeks to germinate Zinnia at a temperature of 20 to 27 degrees Celsius (68 to 80°F).
Transplant outdoors, just after the last possible frost of spring.
Purple Zinnia by Dendroica Cerulea.
It is easy to look after Zinnia. Keep them well watered, and feed them in the spring.
Pinch back Zinnia plants to encourage branching. Feed again once they start to flower. Remove (deadhead) decayed flowers.