Cleome (Cleome hassleriana) is native to South America from Brazil to Argentina. It is grown as a hardy annual in USDA plant growing zones 8 to 11 and as a tender annual in zones 4 to 7. Cleome grows up to 5-feet tall, blooming mid-summer through fall with clusters of flowers 1 to 2 inches wide on 2- to 3-inch-long stamens, or stems, and comes in colors of pink, rose, white or lavender. These flowers work well as border or background plants and can also be grown in containers, but it is best to keep them away from windows and doors since the scent is strong and musky.
Prepare the soil as soon as the ground is workable after the last frost. Till the ground with either a rototiller or a metal rake to break up the soil. Use a rake to work in a layer of compost to make the soil well draining.
Select a garden area that receives full sun daily with some afternoon shade in really hot summer climates. Plant the seeds outdoors the first week of May to ensure that the frost has passed.
Sow the seeds directly on top of the soil you prepared. Gently push the seeds into the soil, being careful not to cover with a layer of soil. The seeds need light in order to germinate. Germination typically occurs in about two weeks when the temperatures are around 70 degrees Fahrenheit during the day.
Water the seeds gently with a watering can, being careful not to wash out the seeds or allow water to pool on the ground. Keep the soil moist while the seeds are germinating. Water the seedlings and plants only when the soil dries out.
Thin the seedlings after about two weeks, spacing the plants about 1-foot apart. To thin, pull out any smaller plants with your hands, removing the seedlings that are weaker and not growing well. Leave the the stronger, healthier plants that have one or two sets of leaves on the stem. Use your fingers to pinch the plant back as new growth appears to grow a bushy plant.
Apply fertilizer to the seedlings after you thin them. Use 1/2 tbsp. of slow-release fertilizer (e.g., 5-5-5) for each plant. Cleome does not need any more fertilizer during the growing season.
Add a 2- to 3-inch layer of mulch around the plants when they are are about 6 to 8 inches tall. Use organic material such as wood chips, chopped leaves or dried grass clippings.