How to Grow and Care for Who Dun It Dahlia

The ‘Who Dun It’ dahlia is an informal decorative variety known for its large blooms. These flowers feature a base of creamy white or pale yellow petals covered in unpredictable splashes of violet and lavender-purple. Each bloom is unique, with the coloration often intensifying as the flower matures. The plant reaches heights of 36 to 48 inches and produces flowers that can span six to eight inches in diameter, making it a great choice for garden borders and cut flower arrangements.

Planting and Growing Conditions

Plant ‘Who Dun It’ dahlia tubers in the spring after all danger of frost has passed and the soil has warmed. This dahlia requires a location that receives at least six to eight hours of direct sunlight daily. Morning sun is particularly beneficial as it helps dry dew from the leaves, reducing the chance of mildew.

‘Who Dun It’ thrives in fertile, well-drained soil with a pH between 6.5 and 7.0. If you have heavy clay soil, amend it with organic matter like compost to improve its structure and drainage. Loosening the soil to a depth of about 12 inches before planting helps the root system expand.

Dig a hole four to six inches deep and place the tuber horizontally with the “eye,” or growth point, facing upward. If you cannot locate the eye, laying the tuber on its side is a safe alternative. Space tubers 18 to 24 inches apart for adequate air circulation. Do not water the tuber after planting until the first green shoots appear, as excess moisture can cause it to rot.

Active Season Care and Maintenance

After shoots emerge, begin a regular watering schedule, providing a deep soaking once or twice a week depending on rainfall and heat. The goal is to keep the soil moist but not waterlogged to avoid root rot. Use a low-nitrogen fertilizer, such as a 5-10-10 ratio, every few weeks once the plant is established to encourage more flowers rather than excessive foliage.

Due to its height and the weight of its large flowers, the ‘Who Dun It’ dahlia requires support. Install a sturdy stake at planting time to avoid piercing the tuber system later. As the main stalks grow, loosely tie them to the stake with soft string or cloth strips to keep them upright and protected from wind or heavy rain.

To create a stronger, bushier plant with a higher flower yield, pinch off the central growing tip when the plant reaches 12 to 16 inches in height. This action signals the plant to send out more lateral branches from the main stem, resulting in a fuller form and more blooms.

Common dahlia pests include slugs, which are drawn to young foliage, and spider mites, which can appear in hot, dry conditions. Slugs can be managed with traps, while spider mites can be controlled with insecticidal soap. Good air circulation from proper spacing and removing the lowest leaves also helps deter pests and powdery mildew.

Lifting and Storing Tubers

In climates with freezing winters, lifting tubers for storage is a necessary task. The ideal time is after the first hard frost has blackened the foliage, which signals the plant to prepare for dormancy. Leave the tubers in the ground for one to two weeks after the frost before digging them up.

Begin by cutting the blackened stalk down to about six inches. Using a garden fork, carefully dig a wide circle around the plant, about a foot from the stem, to avoid damage. Lift the entire clump from the ground and wash off the excess soil with a hose to inspect the tubers.

After cleaning, cure the tubers for a few days in a dry, protected location like a garage. This drying period heals small cuts and toughens the skin for storage. This is also the time to divide the clumps. Use a sharp, clean knife to separate the tubers, ensuring each piece has a portion of the main crown and at least one “eye” for new growth.

For storage, place the cured and divided tubers in a box filled with a medium like peat moss, wood shavings, or vermiculite. This material prevents the tubers from shriveling while protecting them from rot. Store the box in a cool, dark place that remains above freezing, with ideal temperatures between 40-50°F.