Cleomes are warm-weather annuals that can grow up to 3 to 5 feet tall, depending upon variety. Cleomes are fairly drought-resistant and work well in locations that may be difficult to keep watered well. For taller cleome spinosa varieties, it's helpful to place them near buildings or large companion plants to offer protection from high winds. Because many cleomes reseed themselves, you can look forward to season after season of beautiful summer color.
Refrigerate cleome seeds for about a week in the crisper 6 weeks before the last predicted frost date.
Sow the seeds in flats or small pots of seed-starting soil, just barely covering them with the soil.
Moisten the soil, but not so much that it's wet or soggy. Always use warm water for cleome seeds.
Place the seed flat in a warm spot out of direct light. The top of your refrigerator or over a hot water heater is a good choice. Cleome seeds prefer 85 degrees Fahrenheit during the day and 65 degrees Fahrenheit at night.
Continue to dampen the medium with warm water as needed, keeping it evenly moist. Germination is typically erratic but should begin in about 10 days.
Plant cleome seedlings into small individual pots when at least four true leaves have developed. Keep them warm and give them plenty of bright indirect light. Continue watering just enough to keep the medium evenly moist.
Transplant the cleome seedlings outside after about four weeks. Because these plants are somewhat tolerant of cold once established, the temperatures don't have to be particularly warm as long as there is no danger of frost. Choose a location in full sun with rich, well-draining soil. Make sure the seedlings are planted at the same depth that they occupied in their growing pots, and space them 18 to 24 inches apart.
Keep the planting site evenly moist, but allow it to dry out a little in between waterings.
Feed the young cleomes an all-purpose blooming plant fertilizer per the manufacturer's instructions. The cleomes should begin blooming in July.