Though technically a perennial, strawflowers are typically grown as summer annuals as they don't overwinter well in areas with cold winters. The plants grow up to 3 feet tall and produce large, 5-inch diameter flowers. Most strawflowers are yellow, though lavender, pink and white varieties are also available. The plants readily self-seed in the garden each fall, or you can save the seeds from your current plants for replanting next spring. Sow seeds a week before the last expected spring frost to ensure the flowers begin blooming early in the summer.
Rake the soil surface in a full sun garden bed that has good drainage. Break up any large clods of soil and smooth the bed for seeding.
Sow the seeds on the soil surface, spacing the seeds 3 to 4 inches apart in each row. Press each seed lightly into the soil but don't cover the seed. Strawflowers require light for germination.
Mist the garden bed with water every three to four days so the soil remains moist to a depth of 2 inches. Avoid overwatering, which results in muddy soil or standing water.
Thin the seedlings once they produce their second or third set of leaves. Pull up the excess strawflowers so the remaining plants are spaced 8 to 12 inches apart in all directions.
Supply approximately 1 inch of water weekly in a single deep watering, which is enough to moisten the top 6 to 8 inches of soil.
Fertilise the strawflowers once monthly with a balanced soluble fertiliser. Apply the fertiliser at the rate recommended on the label for flowering annuals.
Strawflowers can also be started indoors and later transplanted to the garden. Sow the seeds indoors in pots six weeks before the last expected spring frost. Strawflower blossoms retain much of their colour when dried, making them suitable for dried floral arrangements. Hang the blossoms upside down in a well-ventilated area for one to two weeks, to dry them.