How to Grow Dahlias

CC Flickr photo courtesy of Arthur Chapman.

The dahlia has a fairly large range of sizes but even the smaller kinds are fairly large, standing at 30 centimeters. The largest dahlias can grow to be around two meters with flowers ranging in diameters from five centimeters to thirty centimeters. The flowers have many petals layered in a disk-like arrangement similar to a sunflower. The flowers come in nearly every color and pattern, giving them a reputation for being beautifully colored. Dahlias have woody stalks that do bend but provide some firmness.  These flowers will bloom around July.

Growing Requirements for Dahlias

Dahlias are typically grown from tubers, which allows them to survive long periods of dormancy. The tubers need to be planted fairly deeply, roughly 10 to 15 centimeters. The soil should be well watered to keep the roots moist but the soil should also drain thoroughly. Dahlias also need full sunlight for most hours of the day.

Taking Care of Dahlias

Dahlias prefer temperate climates and therefore never survive winter seasons or frosts. These flowers should be watered regularly to keep the flower healthy and strong. Taller varieties may need to be staked to avoid bending or falling when exposed to high winds or rain. Laying down mulches will help control weeding but by using black mulches the soil will be able to conserve the heat that the plant needs to grow. Dead or dying flower heads should be removed in order to allow the plant to continue flowering throughout the entire season.

History and Uses of Dahlias

Dahlias are native to the Central American region. The Aztecs used the flower for culinary purposes, in ceremonies, as decorations, and for musical instruments. They were known for using the woody stems of the dahlia as small flutes. The name comes from the Swedish botanist, Anders Dahl but the flower was originally introduced to Europe by Spanish explorers.

Dahlia Diseases and Pests

Powdery mildew, grey mould, and dahlia smut are the biggest diseases affecting dahlias. Powdery mildew affects many other plant species and is the result of a fungal infection. There will be a white mildew substance that appears on the leaves and stems of infected plants. Usually a fungicide will treat the problem and help keep the disease from spreading. The flowers can also be susceptible to viral infections.

Red spider mites feast on the dahlia routinely, especially in the middle of summer. These insects will leave small holes in the foliage as well as causing discoloration. The hotter and drier the climate is, the more susceptible the plant becomes. Keeping the flower well watered will help fight significant damage. If the damage becomes too substantial, basic insecticide treatments will help.

Additional Information on Dahlias

Additional information can be found on the following websites:

Details on basic growth facts can be found on the University of Minnesota website.

An extensive fact sheet on dahlias can be found on the Ohio State University website.

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