By: Bonnie L. Grant, Certified Urban Agriculturist
If you have ever been to a state fair, you have probably seen a pavilion filled with exotic and amazing dahlia blossoms. These hugely varietal flowers are a collector’s dream, with little starburst blooms to plate sized flowers in every hue imaginable. Dahlias are relatively sturdy plants if grown in the right lighting, heat, and soil. Care of dahlia flowers may vary dependent upon your zone, but here are a few dahlia growing tips to help you get maximum blooms and healthy, bushy plants.
Dahlias are classified according to flower shape and petal arrangement. The plants are borne from tubers, which require well-drained soil and plenty of sunlight. Caring for dahlia plants starts at installation with cultivation of the soil and healthy tubers. Learning how to grow a dahlia plant will likely lead to a hobby, as the spectacular blooms are quite addictive and the presence of one or two will lead to plenty more in subsequent seasons.
Select healthy tubers of a variety that does well in your zone. The outside of the tuber should be firm with no mold or rotten spots. Prepare the garden bed. These plants prefer well-drained, acidic loam but will grow relatively well in any soil as long as it isn’t soggy.
Dig down 8 to 12 inches (20.5 to 30.5 cm.) and add compost to increase the porosity and nutrient density since dahlias are big feeders. A good dahlia growing tip is to take this time to incorporate 2 pounds per 100 square feet (1 kg. per 9.5 sq. m.) of a 5-10-15 fertilizer.
Small plants can be spaced 12 inches (30.5 cm.) apart, but the big dahlias need to be planted 3 feet (1 m.) apart to accommodate the large bushes. Lay the tuber sprout-side up 3 inches (7.5 cm.) deep in a trench and cover it over with the prepared soil.
Dahlias need to be kept weed free. Use organic mulch around the plants to prevent weeds and conserve moisture.
Pinch back the terminal buds when the plant is 15 inches (38 cm.) tall to enforce good branching and structure and increase budding.
Provide plenty of water to your plants. Water plants deeply once or twice per week. Big dahlias need a support structure to keep the heavy blooms from bending to the ground.
Fertilize monthly with water soluble fertilizer or twice during the growing season use ½ cup (240 mL.) 5-10-10 scattered around the root zone of the plants.
Good dahlia care also includes pest management.
Dahlias are hardy to zone 8 and will survive if cut back and mulched heavily. Pull away the mulch in spring to allow new shoots to come up. In cooler zones, the tubers need to be stored indoors until spring.
Dig at least a foot (30.5 cm.) away from the plant and lift the tuberous clump. Brush off excess dirt and lay them in a dry, but shady, location for a few days. Remove the remainder of the dirt and check the tubers for damage or disease.
Pack healthy tubers upside down in a basket nestled in damp peat moss, vermiculite or perlite. Check tubers every month, and if they begin to shrivel, mist them with water. Remove any that get diseased. You can also dust the tubers with antifungal powder before storing. In the spring, replant the tubers and follow the above program of good care for dahlia flowers.
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Read more about Dahlia Flowers
For most seasoned gardeners, the prospect of adding a new crop to the garden is exciting. As a cut-flower grower, I frequently add new plants to the flower cutting field. Browsing online, it is easy to be swept away by the beautiful imagery of bloggers and professional growers. When I saw the large rows of dahlia flowers in full bloom at a local farm, I knew I would need to grow them myself, but little did I know that it would be such a challenge.
Dahlia plants are amazing, another example of horticultural magic. The dinner plate types can grow a full metre high in just a few months while producing blooms almost 30 cm across.
Underground, the same thing is happening. Should you decide to dig up your dahlia tubers at the end of the season, you'll be impressed with what's been happing under the soil surface. Expect to find clumps of potato-like tubers, which often can be divided into several pieces (and plants) for next year's garden.
Could your garden use a little magic? Add a few dahlias.
For extra early summer flowers try potting up your dahlia tubers as soon as you receive them. Then in early summer when they are in full growth plant them into any holes that you may have in the garden. This method achieves two things:
While dahlias are low maintenance and easy to grow, they perform best with regular watering and staking. If your area does not receive at least an inch of rainfall weekly, water deeply once a week. Mulching can also help retain moisture. If planted in rich, organic soil and fertilized at planting, dahlias should not require additional fertilizer. Pinching and disbudding dahlias results in later, larger flowers. Staking or caging should be done when the plants are small. When staking, take care not to puncture or nick the roots.
Use a 9cm pot to start with or go straight into a 2 litre pot, which I often do to save time. Grow them on somewhere warm, although if there are no frosts you can start moving them outside during the day to toughen them up to the elements.
When all frosts have stopped, usually sometime in June for most of the country, the dahlias can go into their final positions in pots or borders. Keep them well fed with an organic tomato fertiliser fortnightly. I use seaweed based or homemade comfrey feed. As with all dahlias, they will form tubers that can be left in the ground over winter in most areas or dug up and stored.
The pests that bug dahlias the most are pretty typical to other similar seasonal blooms. The biggest issue is definitely slugs, especially while the dahlias are young and small. Earwigs, caterpillars, and thrips can also pose a problem. Additionally, some gardeners say deer love their dahlias and others claim they avoid them. It may depend on what else is available to munch on in your garden, but keep your plants protected just in case.
Dahlias can also be prone to powdery mildew and other fungal diseases. Keep the foliage as dry as possible by allowing for good air circulation. If you notice an infection, treat it with neem oil or another natural solution.