PLANTING
You should really grow zinnia from seed, as they do not like to be transplanted as nursery plants and do not often thrive. From seed, they will grow very quickly in the right conditions.
Do not seed until the last frost has passed. See your local frost dates.
Choosing a location that gets full sun is essential. Zinnias can stand a minimum daytime temperature of 60 degrees F, and a range of 74 to 84 degrees F is preferred.
Zinnias are adaptable, but the ideal soil is nice and fertile, humus-rich, and well-drained. Soil pH should be between 5.5 and 7.5. If soil is amended with compost, the flowers will grow more quickly. Learn more about soil amendments and preparing soil for planting.
Sow zinnia seeds only -inch deep.
Space plants 4 to 24 inches apart, depending on variety. (Many common varieties are planted 6 inches apart within the row and 2 feet in between rows.) See back of seed package for variety-specific advice.
You ll see zinnia seedlings in only 4 to 7 days for most varieties.
When seedlings reach three inches tall, thin them so that they re 6 to 18 inches apart to maximize air circulation.
Sow in succession for a longer flowering display.