Zinnias are flowering plants native to Mexico and South America. Because they require warm temperatures to bloom, zinnia flowers are grown primarily as annuals in the United States. Zinnias are easy to grow from seed if the proper growing conditions are provided. When the seeds are sown directly in the garden at the correct time of year, zinnias will grow profusely with only minimal care. The plants are valued for their large, showy flowers that appear during the summer months in colors of white, yellow, orange, red, violet and pink.
Plant zinnia flower seeds directly in the garden in spring after all danger of frost has passed and the soil is workable. Select a planting location that receives full sun, and has average, well-drained soil and good air circulation.
Plant zinnia seeds about ¼ inch deep. Space seeds at least 6 to 18 inches apart, depending on the variety. Some types need more room to grow than others. Check your seed package for specific spacing requirements for your variety.
Water the soil thoroughly immediately after planting to initiate germination, which will occur in about seven days. Keep the soil moist until seedlings emerge by watering two to three times per week. Reduce watering to once per week after germination.
Feed zinnia flowers once per month during spring and summer using an all-purpose flower fertilizer according to the manufacturer's instructions. Wait until the plants need water before feeding, and then water thoroughly before and after applying fertilizer to prevent root burn.
Remove spent flowers from zinnia plants as soon as possible to prolong blooming and keep the plants healthy. Zinnias are often covered in mildew late in the growing season. Remove any affected plants from the garden completely and burn in another location.