Cleome

Cleome is a back-of-the-border annual that can reach five feet in a single season, sending up tall spires of pink, white, or violet flowers that open from the bottom up. Hummingbirds visit them morning and evening, and long-tongued bees work them all day. The flowers are fragrant — some people find it sweet, others find it musky — and they keep coming until a hard frost takes the plant down. Once established, cleome asks for almost nothing: no deadheading, no fertilizer, no supplemental water in most climates.

The catch is that cleome reseeds with enthusiasm. A single plant can drop hundreds of seeds, and those seeds germinate reliably the following spring. Within two or three years, you may have cleome where you didn't plant it — in the vegetable bed, in the gravel path, crowding out shorter plants. The seedlings have spiny stems and sticky foliage that make pulling them out an unpleasant task, especially once they're a few inches tall. If you want cleome in your garden but not everywhere in your garden, deadhead the spent flower stalks before the seed pods ripen.

Sow seed directly in the ground about one week after your last frost date. Cleome germinates better when the seeds experience a few cool nights first — a light cold stratification — so sowing a little early tends to work better than waiting for consistently warm weather. Press the seeds lightly into the soil surface; they need some light to germinate. Thin seedlings to about two feet apart once they're a few inches tall.

The plants grow quickly in warm weather and tend to develop a single tall stem with side branches near the top. They don't need staking in most gardens, though in very windy sites or rich soil that encourages overly lush growth, the tallest stems can lean. Pinching the top of the plant when it's a foot tall may encourage more branching, but it also delays the first bloom by a few weeks.

Aphids are the most common pest, clustering on the new growth at the top of the stems in midsummer. A strong spray of water usually knocks them off; they tend not to do lasting damage unless the infestation is severe. The sticky foliage also traps small insects, which occasionally leads people to think the plant is carnivorous — it isn't, but the trapped bugs may attract beneficial predators.