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Darling dahlias

Jan Hearne • Jun 11, 2012 at 8:42 AM

Sometimes it’s difficult for gardeners to think ahead. Just now we are reveling in the beauty of late-spring bloomers, but our thoughts should be turning toward late summer and fall if we want continuous bloom until frost. One of the stars of the August-September garden is the dahlia, and we have about five more days to get the tubers in the ground.

Dahlias are easy to grow, but they have an undeserved reputation for fussiness because they have to be lifted from the ground and stored after the first frost if they are to bloom again. Some gardeners with deep pockets treat them as annuals and leave them in the ground to freeze and rot, but the rest of us, if we love dahlias, have to take that extra step. But that is months ahead, and not so difficult to do.

Right now the difficulty is deciding which dahlias to plant. The American Dahlia Society recognizes 18 classifications of form from Formal Decorative to Semi-Cactus to Ball to Pompon to Waterlily. The society also recognizes 15 different color or color combinations, including splashes, stripes, narrow lines and bicolor.

Having waited late in the season to plant, we are limited by availability in our area, unless we want to rush ship tubers from a specialty grower. Local garden center and big box stores carry dahlia tubers in a variety of forms and colors, however, so there should be no gnashing of teeth.

The American Dahlia Society assures us, “If you can grow tomatoes, you can grow dahlias.”

Like tomatoes, dahlias require a minimum of a half day of direct sunlight, and they need room to spread out. They also need stakes to keep from flopping over when the plant is heavy with blooms.

Dahlias prefer moist, well-drained garden loam. If the soil is heavy clay, work in liberal amounts of well-rotted manure, compost and other organic matter to a depth of about 12 inches. Dahlias also may be grown in pots, and raised beds are ideal.

To plant the tubers, dig holes 4- to 6-inches deep and wide enough for tubers to fit comfortably. Place the tuber horizontally in the hole with the eye or bud facing up. Cornell Cooperative Extension says it is advisable to put a 4-foot-tall stake about one-inch from the end of the tuber at the time of planting to provide support until it reaches full growth. Then cover with 2 to 4 inches of soil. As the shoots grow, the cooperative says, continue to fill in the hole until it is level with the surface of the soil.

Dahlias do not like soggy ground, but in dry summers water deeply every 7 to 10 days. When siting and growing dahlias, keep in mind they are a native of Mexico, grown by the Aztecs as early as the 1300s. Hot and dry does not faze them, but too dry is too much.

Avoid overhead watering, and water early in the day. Wet leaves left overnight encourage the growth of fungus.

Dahlias’ enemy No. 1 is the slug, a menace in the garden and the bane of barefoot children. ADS advises gardeners to put out slug bait when the dahlias are planted and every two weeks after that. Organic gardeners can use beer in shallow vessels (the slugs crawl in to drink, then drown) or gritty material like diatomaceous earth. Others swear by copper rings. Serious infestations may call for products like Sluggo.

Once the weather gets hot, mulch dahlias, especially if a period of hot, dry weather is in the forecast. Mulch maintains consistent ground temperature and prevents runoff during heavy rains. It keeps weeds down and prevents water evaporation, too. Unfortunately, mulch can provide a place for slugs and other pests to hide, so the ADA recommends putting slug bait on the ground before and after mulching. Do not used shredded hardwood, the ADA says, because it retains water that does not reach the plant, and it promotes the growth of fungus.

Good gardening practices apply with dahlias, which, when it comes down to it, need no more care than any other garden plant. The payoff is a profusion of blooms in late summer and early fall — for show in the garden and for cutting.

What some consider the difficult part is the lifting of tubers in the fall. There are several methods of preparation and storage. A tried-and-true space saving method involves wrapping tubers in plastic wrap.

For the details, visit the American Dahlia Society’s website at www.dahlia.org.

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