The Lilac Bull Dahlia is a captivating variety that brings an impressive display to any garden. Its distinctive color and form make it a sought-after addition for vibrant floral arrangements and striking outdoor aesthetics.
Characteristics of Lilac Bull Dahlia
The Lilac Bull Dahlia presents a unique bloom structure, often decorative or waterlily-shaped, featuring short, inrolled petals. Its flowers typically measure between 2 to 4 inches in diameter, offering significant visual impact. These eye-catching flowers boast a deep lilac-purple hue, sometimes with merlot undersides, and can appear magenta depending on light conditions. The plant itself grows to a height of approximately 3 to 4 feet (90 to 110 cm), with fresh, deep green foliage. Lilac Bull Dahlias typically flower from mid-summer until the first autumn frost.
Planting and Site Selection
Successful cultivation of Lilac Bull Dahlia tubers begins with selecting the right location. These plants flourish in full sun, requiring at least six to eight hours of direct sunlight daily to produce abundant blooms. The soil should be well-draining and rich in organic matter, such as compost or well-rotted manure, to foster healthy root development. Heavy clay soils benefit from amendments like sand or grit to improve drainage, as excessive moisture can lead to tuber rot.
Planting should occur after the last spring frost has passed, typically when the soil temperature consistently reaches around 60°F (15°C). Tubers are generally planted 4 to 6 inches deep, with the “eye” or growth point facing upwards. Adequate spacing is also important, with tubers placed approximately 12 to 20 inches apart to allow for proper air circulation and growth. While some initial watering is acceptable in very dry conditions, it is generally advised to avoid excessive watering immediately after planting until shoots emerge, especially in cooler soils, to prevent tuber rot.
Ongoing Care for Thriving Blooms
Consistent moisture is important for Lilac Bull Dahlias, particularly during dry periods and as the plants establish themselves. Infrequent, deep watering that targets the root zone is preferred over shallow, frequent watering, helping to encourage a robust root system. Keeping the foliage as dry as possible can also help deter certain pests and diseases.
Dahlias benefit from regular fertilization to support their vigorous growth and prolific flowering. A low-nitrogen fertilizer, often referred to as a bloom food, with a higher percentage of phosphorus and potassium (e.g., 5-10-10 or 10-20-20), is recommended. Application can begin about 30 days after planting and continue every three to four weeks throughout the growing season for in-ground plants, or every two to three weeks for those in containers. Pinching out the central growing tips when the plants are about a foot tall encourages a bushier plant structure and more flowering stems.
As Lilac Bull Dahlias grow to their mature height, providing support through staking becomes necessary to prevent stems from bending or breaking under the weight of their blooms. Strong stakes, such as rebar or sturdy bamboo, should be placed near the tuber at planting time to avoid damaging developing roots. Regularly removing spent blooms, a practice known as deadheading, redirects the plant’s energy from seed production back into creating new flowers, ensuring a continuous display from mid-summer until frost.
Pest, Disease, and Troubleshooting
Lilac Bull Dahlias, like other dahlia varieties, can encounter certain garden challenges. Common insect pests include aphids, which cluster on new growth and suck plant sap, and spider mites, often found on leaf undersides, causing yellowing and mottling, especially in hot, dry conditions. Slugs and earwigs can also damage foliage, particularly young shoots. Regular inspection of plants helps in early detection, and managing these pests often involves organic solutions such as insecticidal soaps for aphids and spider mites, or physical removal and barriers for slugs.
Dahlias are also susceptible to fungal diseases such as powdery mildew, appearing as a white, powdery coating on leaves, and botrytis (gray mold), which can cause brown, rotting spots on flowers and leaves, particularly in humid conditions. Viral issues, like dahlia mosaic virus, may cause distorted or mottled foliage. Maintaining good air circulation around plants by proper spacing and avoiding overhead watering can help prevent fungal problems. Removing and disposing of affected plant parts promptly can limit the spread of diseases.
Harvesting and Winter Storage
Harvesting Lilac Bull Dahlia blooms for cut flowers is best done in the early morning or late evening when the flowers are fully open. Using sharp, clean shears, cut stems at an angle, leaving at least two sets of leaves on the plant to encourage further branching and blooming. Promptly placing cut stems into water helps to maximize their vase life.
For gardeners in colder climates where ground freezes, Lilac Bull Dahlia tubers need to be lifted and stored for winter. This process typically begins after the first hard frost has caused the foliage to blacken and die back. Carefully dig up the entire clump of tubers, taking care not to damage them with gardening tools. Excess soil should be gently removed, and stems can be cut back to about 4 to 6 inches from the tuber crown.
After digging, allow the tubers to dry for several days in a cool, well-ventilated area, away from direct sunlight. Once dry, store them in a cool, dark, and frost-free location, ideally between 40-50°F (4-10°C). Breathable containers like cardboard boxes or paper bags work well, with tubers nestled in a dry medium such as peat moss, vermiculite, or dry sand to maintain humidity and prevent desiccation or rot. In warmer climates, where the ground does not freeze deeply, tubers can often be left in the ground with a protective layer of mulch applied over them for insulation.