From July to a killing frost in October, dahlias dominate my garden with their many petaled lushly colored flowers. Except for a true blue, you can find just about every flower color in a dahlia. Sizes can vary from an enormous 12 inch dinner plate to small button pom poms. Bee magnet blooms cover my plants that are excellent for cutting and using in arrangements.
Originating with the Aztecs, and arriving in European gardens in 1789, by 1927 F. F. Rockwell, author and founder of Home Garden Magazine, reported that dahlias ranked in “the leading position of all bulbs grown in America.” For fascinating details on this beloved flower, go to Dahlia Archives of Old House Gardens. Old House Gardens carries a wealth of heirloom varieties of all kinds of bulbs that you can’t find anywhere else.
Easy to grow if given adequate sunlight and rich well-drained soil and plenty of moisture, these shrubby plants grow from tuberous roots, or tubers. Depending on how severe your winters are, they may require digging and storing indoors until planting time next spring. For this reason, many buy new ones every year. Hundreds of flower forms and colors can confuse people about what varieties to plant but I see this as a great opportunity to try new ones every year and also to go back to my favorites. But remember, the larger the flower, like the dinner plate size (7 inches +), the less flowers it will produce. Juanita, a lovely ruby-red smaller flower (4-5 inches), will produce dozens of flowers compared to a dinner plates’ couple of flowers at a time. Gallery Art Deco, Cafe Au Lait, and Diva are my favorites from Longfield Gardens. There are so many favorites and new ones to pick from! Swan Island from Oregon carries hundreds of varieties and I like how they stamp the name on the tuber so you can even see it when you dig it up for saving. You always have the name even if your tags fade in the sun. Brandon Michael and Hulin’s Carnival were outstanding selections from Swan Island this year.SunlightSelect a spot that gets at least six hours of sunlight a day, preferably more. If you can grow a tomato in a spot, you can grow a dahlia. Tolerating partial shade, dahlias will still bloom but less blooms will be available for cutting. And to produce more blooms, dead head and bring the fresh cuts in to enjoy.
Heavy feeders, dahlia tubers should be planted in loose fertile soil. Add compost to the soil before planting. Don’t plant in soggy soil; they need good drainage to be successful. Soil temperature must be over 60 degrees Fahrenheit in the spring and I check this with my instant read cooking thermometer. Tubers can rot if planted in wet cold soil in the spring.
Plant tubers by digging a hole three to six inches deep and laying the tuber in it with the growing tip up. The growing tip or bud is obvious as a fresh emerging shoot coming out of the fleshy brown tuber. Cover with soil but don’t water until well after growth emerges. Plant the tubers about 18 to 24 inches apart because they produce bush-like plants.
Staking can be done with tomato cages or with stakes and twine. Most dahlias need to be staked or you will have a plant with branches that will flop on the ground and have misshapen flowers. Water if you don’t get at least an inch of rain per week and the plants benefit from feeding lightly with a granular or liquid fertilizer of a general use fertilizer, not high in nitrogen. High nitrogen will produce more foliage than flowers. Dahlias like cooler conditions so flourish especially well in the late summer when temperatures start to moderate.
Frost will hit your plants sometime in October or November and they will go from glorious specimen plants to blackened wilted skeletons overnight. Check your weather report and before a hard frost is forecast, cut off every flower and bring it in to enjoy for another week. Once the plants are frost killed, you can start digging around the root ball carefully to remove the shrunken star fish like tuber that is nestled a few inches under the soil. Wash off any soil with a hard stream from your hose and dry in the sun. If you leave you tubers in the ground, I have found that some even come back if the winter hasn’t been too cold. Some people don’t save them, preferring to buy new ones every year.
Cut the stems a few inches above the tubers and store them in a container full of peat moss and perlite. I only place two layers of the tubers in a container, as I find that the bottom layers tend to rot more often than the top. If the tubers are too wet, they might rot, so I check them after a couple of weeks of storage to see how they are doing. If they are moldy, I scrape off the mold and add some dry peat moss. You are going to lose some of the tubers, but I have a success rate of about 75% saved tubers.
Alternative Method of Planting/Saving
Another method is to plant your tubers in 1 gallon plastic pots early in the spring. When the weather warms up, plant the whole pot in the garden and cover with soil. Leave the tuber in the pot and roots will come out the bottom drainage holes. When frost hits, dig up the entire pot, cutting off roots that are outside of the pot and bring the pot inside and place in a cool dark place for the winter. When shoots come up in the spring, top dress with compost and plant outside for another season of bloom. I read about this method on Old House Gardens and want to try it next season.
Another method which a friend swears by is to dig up the tubers and shake the loose soil off and place in a large trash bag, leaving all the clinging soil attached to the tubers. Store the trash bag in an unheated garage that won’t go below freezing. Easy and effective!
Bees love the single type of dahlias because they can easily get to the nectar and pollen
Juanita dahlia available from Old House Gardens and Swan Island
‘York and Lancaster’ an heirloom dahlia from Old House Gardens
Cafe au Lait dahlia flowers are in shades of cream, pink, and tan
Pam Howden is a beautiful peach tinged with yellow, seen at Longwood Gardens
Pom Pom form of dahlia
Bringing armloads of blooms in the summer will decorate your living space for weeks