Zinnias are popular garden flowers because they come in a wide range of flower colors and shapes, and they can withstand hot summer temperatures, and are easy to grow from seeds. They are grown in fertile, humus-rich, and well-drained soil, in an area with full sun. They will reseed themselves each year.
Zinnias don’t transplant well, but can be started indoors, if necessary, in peat or coir pots, 6-8 weeks before planting out. Maintain a soil temperature of 21-26°C (70-80°F). Seeds should germinate in 5-24 days. Just cover Zinnia seeds, and aim for a final spacing of 25-30cm (10-12″) between plants