To encourage blooms, water regularly once they've leafed out, and apply a monthly dose of low-nitrogen fertilizer, starting shortly after planting and ending with a final feeding in mid-August. For a compact plant with lots of flowers, Hans Lange-veld, co-owner of Longfield Gardens, recommends pinching off the first bud on the center shoot, just below the third set of leaves. "This keeps the plant from putting all its energy toward producing just one flower," he says. And, of course, deadheading is essential. Dahlias are cut-and-come-again perennials, so if you're not regularly harvesting bouquets, be sure to remove spent blooms. Then they'll give encore performances well into fall, until a good hard frost ends the show.
Shown: Miniature pompons, about 2 inches across, top 'Elfin' all season.