My grandfather’s neighbor grew dahlias – giant things, with huge, coarse leaves. Their stems were trussed to stout bamboo poles, held captive to protect the hope of a flower. He’d pinch out most of the flower buds, trampling them into the ground, squeezing the plant’s energy into one tremendous effort of bloom. Then the day would come when the flower finally broke open. It would hang heavy, its stem weak from bondage to the pole. He’d cut the flower from the plant and carry it off for prizes in a local show (like you would a cow or a giant turnip). I don’t grow those dahlias.
My dahlias are the blobs of color that smile in the background of paintings by Van Gogh and Monet. Their flowers are of all different sizes and shapes. Some are tiny, carried in loads of pompom bloom. A few are large, even the size of a Frisbee. Their heavy heads hang down to make a one-flower bouquet, glowing when the summer light gets low. I can cut as many as I want for bouquets, knowing that there will always be more in the garden.
To grow dahlias as I do, it’s important to take several things into consideration. Dahlias are tropical plants, originating in Mexico and the Central American Peninsula. While often treated as annuals in the northern U.S., dahlias are perennial geophytes that regrow from underground tubers. If you decide to grow more unusual varieties unavailable from local nurseries, it will be necessary to order tubers in early spring. Pot the tubers in rich potting mix, water them in well and grow them on for a few weeks in a cold frame or greenhouse until the nights warm and all danger of frost has passed. Otherwise, wait until it’s warm and find the stockiest plants you can at your local nursery.
Dahlias require rich soil, high in organic matter, to thrive. They need regular moisture, but are highly sensitive to overwatering early in their growth season. Later on, once summer heats up, they may require daily watering. At least six hours of direct sun per day are essential for them to thrive. Afternoon shade can help prevent the flowers of brighter varieties from fading.
Once your dahlias have settled into their various situations, they will grow primarily in leaf and plant mass for much of the summer. Smaller varieties can flower heavily throughout the summer, since they put less energy into growing. Larger varieties put their effort into growing strong stalks and massive plants throughout the summer, occasionally dropping hints of their coming autumn glory, but not doing much until the nights cool.
While some of the smaller dahlias run little risk of falling over, even when full of flowers, it is essential to incorporate supplemental support systems for the larger-flowered varieties. Different growers utilize various methods for supporting their dahlias. I have experimented with different systems of stout posts and twine for the larger varieties. However, repurposed tomato cages also yield excellent results. Stout cages are often the best option, supporting the structure of the plants without constraining their growth.
Dahlias take up space. It is essential to consider their size at maturity. Consider your selections’ eventual sizes before giving them dainty neighbors.
Collectors and dahlia aficionados have elaborate systems for categorizing dahlias. The American Dahlia Society’s classification website lists more than 40 different classifications. For most gardeners, however, the biggest differences occur in plant size and flower shape. To start, consider these five top performing varieties: ‘Bishop of Llandaff’, ‘Fireworks Mixed’, Mystic Spirit, ‘Edinburgh’ and ‘Kelvin Floodlight’.
‘Fireworks Mixed’, ‘Bishop of Llandaff’, Mystic Spirit
‘Fireworks Mixed’ is a seed strain with flowers striated in a range of citrus colors – lemon, orange, scarlet and magenta. Its flower form is single, like ‘Bishop of Llandaff’, but the plant has bright green foliage. ‘Fireworks Mixed’ was originally promoted for its ability to bloom heavily in its first year when grown from seed. It is an excellent bushy plant with abundant flowering throughout the season.
‘Bishop of Llandaff’ appeals even before its first scarlet flowers burst open. Its foliage is nearly black and finely dissected, making an excellent background for the bright flowers. Far removed from the massive blooms of the dinner-plate varieties, ‘Bishop of Llandaff’ is continually arrayed with a myriad of glowing scarlet flowers. Seedlings with similar dark foliage but variously colored flowers are often sold as ‘Bishop’s Children’.
Mystic Spirit (‘Best Bett’) is another clonal selection with dark foliage. The leaves are less finely dissected than those of ‘Bishop of Llandaff’, with strong purple tones. Its flowers are also single, with eight apricot petals. Again, they are carried in abundance on a bushy and easy to grow plant.
‘Edinburgh’ is a larger variety, growing to 4 feet high and wide, with flowers between 4-6 inches across. Unlike the three previous varieties, ‘Edinburgh’ has fully double flowers, in what is classified as the “Decorative” style. Each of its mulberry petals appears to have been dipped in white paint, giving it a striking appearance. ‘Edinburgh’ is one of the most abundantly flowering dahlias, particularly when the nights cool off in the fall.
‘Kelvin Floodlight’ will give the impression that you have gardening superpowers. It is a giant, with pale gold flowers that can reach 10-12 inches across. ‘Kelvin Floodlight’ is a little later to bloom than the smaller-flowered varieties, but will always have a few flowers once it begins. Because each of these enormous flowers requires so much energy from the plant, it rarely produces more than two or three flowers at a one time.
These five dahlias are only a few out of the vast array of dahlia cultivars available to gardeners. They might not help you win a flower show, but they will make you smile every day with their brilliant colors and fantastic blooms. If prizes are what you value, concentrate on turnips.
A version of this article appeared in a March/April 2014 print version of State-by-State Gardening
Photography courtesy of Caleb Melchior and Jim Kochevar.