Centaurea imperialis, also known as royal sweet sultan, is a flowering annual plant and a hybrid of C. moschata and C. margaritas. C. imperialis is a variety of cornflower that blooms in 2-inch, thistle-like flowers in white, lavender, pink and yellow. If you are looking for a fragrant addition to your cut flower garden, consider the C. imperialis. Sow the seeds in April for July blooms.
Choose a planting location for the Centaurea imperialis that gets full sun.
Dig into the planting bed to a depth of 8 inches, turning and crushing the soil with the gardening fork.
Add a 3-inch layer of compost to the soil and mix it in to a depth of 8 inches.
Pour lime onto the soil and mix it to a depth of 8 inches. Agriculturists at Washington State University suggest that the amount of lime to add depends upon the type of soil in your garden. If you have sandy soil, add 4 lbs. of lime. If the soil is loamy, add 6 lbs., and if you have clay soil, add 8 lbs. of lime. These amounts apply to every 100 square feet of garden space.
Rake the soil smooth after amending. Plant the Centaurea imperialis seeds 1/4 inch into the soil, and 12 inches apart.
Water the area with the fine mist setting on the hose and keep the planting bed moist, not soggy.