Germination

Cleome plants are easy to start in the garden from seed. Perhaps too easy because the plants can self-seed to the point of being a nuisance. The seeds need light to germinate, so you can just sprinkle them in the garden after the danger of frost is past and look for seedlings after ten days. Alternatively, sow them in the autumn, and they will germinate when conditions are just right in your garden the following growing season.

If you do allow the plants to self-seed, thin the newly emerging seedlings to allow at least 18 inches between plants. This improves the vigor of individual plants, encouraging the most blossoms from each plant. If you want to limit cleome’s self-seeding habit, remove the long seed pods that form.

How to Get Cleomes to Bloom

Fortunately for the home gardener, cleomes are quite easy plants to grow and maintain. A good watering habit will help establish them; once established, they are drought-resistant and respond well to pruning. Deadheading cleomes will encourage new growth while preventing it from self-seeding, thus keeping the garden neater.

Cleome Care
Averaging three to four feet in height, cleomes provide a welcome tall focal point in the annual garden, where compact bedding plants tend to rule. The pink, purple, white, and lavender flowers do not emit a noticeable fragrance, yet hummingbirds, butterflies, and hummingbird moths are drawn to these flowers all summer long.

Cleomes easily start from seed in the garden and tend to be hearty from germination, growing quickly. Once started, the plant seems to take care of itself. What is more, the upright stalks need no staking if they are growing in full, bright sun. This plant shrugs off pests and diseases.

Light
Cleome flowers grow best in full sun, shady conditions can make them grow too tall and topple over. If you start with transplants, blossoms will appear from early summer until the first frost. Gardeners who grow cleome from seed usually see the first flowers in mid- to late-June, depending on the climate.

Soil
Cleomes do best in average garden soil or rich, well-drained garden loam.

Water

Once established, cleomes are drought-tolerant. Add a three-inch layer of organic mulch to their planting bed, and you will decrease their water needs even further.

Temperature and Humidity
For successful germination, cleome seeds need higher-than-normal temperatures. Fluctuating day/night temperatures are essential for optimum germination. During the day, temperatures should range from 80 to 85 degrees Fahrenheit; nightly temperatures should stay between 68 and 70 degress Fahrenheit. The humidity should be from 90 to 100 percent. As the plant grows, the temperatures can be lower, from 75 to 80 degrees Fahrenheit during the day and 60 to 65 degrees Fahrenheit at night. Cleomes are not frost-tolerant.

Fertilizer
If using good, well-drained soil and mulch, no fertilizer is necessary.