Dahlia Planting Tips

Dahlia Planting Tips Follow these planting guidelines for strong stalks, show-stopping blooms. Many flowers perform well in our temperate Pacific Northwest climate, but the dahlia holds a special place in the hearts of many gardeners. Fanciful, brilliant and sometimes startling in size, dahlias come in wondrous variety: More than 50,000 (and counting) varietals are available today. Formerly called cocoxochitl and native to Mexico, the dahlia became so-named in 1789, when the king of Spain changed the name to commemorate Anders Dahl, a Swedish botanist who was active in cultivating these tender tuberous perennials. Dahlias grow from 1 to 5 feet—although, while living in Minnesota, I had a cactus-type called ‘Bright Star’ that regularly shot flower stalks into the 7-foot range. Blooms range from 1 inch to 12 inches across. Nineteen “forms” (describing what the blooms look like) of dahlias have been defined as classes by the American Dahlia Society. Several of these categories are further divided into five size ranges from miniature to giant. These divisions are subdivided further into 15 color categories. There are more than 570 individual dahlia classes. Dahlia shown is ‘Sundown.’ Dahlia shown is ‘Wildcat.’ If you’re like me, though, you don’t have much need for that kind of trivia. You just like to grow dahlias. And, if you’re thinking about dipping a toe into the wonderful world of dahlia-growing, following these simple tips will help to ensure your dahlias grow up to be all they can be. Select the right site Like most plants, dahlias love sun, so find a spot that gets at least 8 hours of direct sunlight every day. If you try to fudge this point and plant them in a shady spot, you’ll end up with tall, spindly plants and weak blooms—if the plant blooms at all. And, don’t plant them in an area that has been chemically treated for weeds. Growing great dahlias is easy. First, select a sunny planting bed. Next, locate the growth eye, a fleshy bump at one end of the dahlia tuber. Dig a hole 6 inches deep and lay the tuber in the hole on its side, with the growth eye facing up. Drive a stake into the ground near the growth eye. Cover the tuber and don’t water it until an inch or two of growth shows above ground. I like to place cages around my tubers to protect them from curious fingers and wandering dogs. Prep the soil Get a soil test (now). Then, a few weeks before you plan to plant out your dahlias, mix in a little composted steer manure and whatever else your soil needs, based on the soil test results. If you have heavier soil, work in a little peat moss to lighten and loosen the texture for better drainage. Don’t overfertilize the soil at this point; use only the recommended amount. For example, if you pump the soil full of nitrogen, your dahlias will likely have weak stems and will stand a greater chance of rotting the following winter. Planting This is the fun part. Late April or early May usually is a good time to plant your dahlias here in Skagit County. Dig a hole about 6 inches deep and lay the tuber on its side in the hole, with the growth eye pointing up (see photo). If you’re planting several dahlias at once, space your holes about 2 feet apart. If you’re growing a taller variety—say, anything that will grow taller than 3 feet—now’s the time to stake the plant. Before you cover the tuber with dirt, drive a stake into the ground next to the growth eye. My soil is very rocky, so I like to stake my dahlias with 6-foot sections of half-inch rebar, driven 2 feet into the ground. Another option for support would be tomato cages, which are hidden by the foliage as the plant grows. Resist the urge to water in the tuber. This is not necessary, especially here in western Washington; doing so will invite rot. Wait until the dahlia shoot has risen an inch or two above ground before you even think about watering it. In fact, if the weather is unusually wet, consider delaying your planting time until the ground dries out a bit. Planting dahlia tubers in waterlogged soil is asking for trouble. Meal time Dahlias are heavy feeders, but don’t overdo it (remember what I said about nitrogen). Err on the side of caution. A basic 5-10-10 fertilizer will probably do just fine, but apply fertilizer according to label instructions and based on your soil test results. You’ll probably only need to fertilize your dahlias once or twice during the growing season. Bugs and other thugs Snails and slugs may descend on your tender dahlia shoots as they emerge; use slug bait to prevent these pests from devastating your plants. I get good results using an organic slug bait with iron phosphate as the active ingredient, but whatever you choose, follow the label instructions. The same goes for all insect controls. Dahlias are a favorite meal for earwigs, cucumber beetles and spider mites, which will succumb to most chemical controls if they’re applied correctly. As for powdery mildew, which can appear in late summer, a preventive approach is best: Try spraying the foliage with sulfur before the powdery mildew appears; it works for me. Ongoing beauty Dahlias will bloom from mid-summer all the way till the first hard frost, providing you with gorgeous cut flowers and bouquets. After cutting your blooms, place the cut stems in 2 to 3 inches of very hot water (approx. 160 degrees) and allow the water to cool for one or two hours. This will “set” the blooms and make your arrangements last for 4 to 6 days. But even if you don’t cut fresh flowers from your plants, remove the spent blooms; this will encourage continued blooming and better bloom color throughout the season. Dahlias of every size are popular, but the “dinnerplate” varieties are real kid magnets. Speaking of blooms, here’s a nifty trick: Dahlia blooms generally rise on sets of 3 flower stalks. If you pinch the lateral (outside) stalks off early in the game, the central stalk will bring forth a larger bloom than it would have. This technique comes in handy when you’re growing a “dinnerplate” dahlia variety and want to have a shot at taking home the blue ribbon at the Skagit County Fair. But that’s all I’m going to tell you. You are now, after all, my competition. -------------------------------------------------------------------------------------------------------------------------