How to Grow and Care for Dahlias

Dahlias used as long lasting cut flowers
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What flower gardener doesn’t want to boast a blossom bigger than his head? Dinner plate dahlias are the anomalies everyone wants to talk about, but this genus has so much more to offer. Part of the large daisy family Asteraceae, the dahlia genus grows as an annual in all climates except the warmest areas of the country in zones 10 and 11. Dahlias reach their peak in late summer, when not much else is going on in the flower garden.

A Dahlia for Every Garden

The American Dahlia Society describes 20 classifications of dahlias, but you don’t need to familiarize yourself with all of them unless you plan to start showing flowers. Some of the more common varieties you’ll see at your garden store include cactus, ball, and water lily. Many flower gardeners want the fully double flowers of cactus and dinner plate types, or the charming pompon spheres. You can also choose from single varieties that resemble the shape of a daisy and don’t need staking.

Give Dahlias a Healthy Start

There’s no magic soil formula for growing good dahlias. They thrive in similar conditions to a healthy vegetable garden plot. In fact, a row of dahlias makes a nice disguise for a flowering vegetable garden in the front yard.

For best results, provide your dahlias with soil that drains well, plenty of leaf mold or compost, and a pH of 6.5, which is slightly acidic.

What a happy coincidence that all three of these requirements are compatible with and overlap one another. By enriching the soil with organic material, you also acidify the soil and enhance drainage. 

Plant dahlias in full sun when all danger of frost is past. Dig a 12-inch hole, and add about ¼ cup of bone meal to the planting hole.

If your dahlia variety needs staking, you can insert the stake at planting time to avoid injuring the tuber.

Dahlia Care

You can keep your dahlias blooming from June until frost, with regular care. Dahlias are heavy feeders, much like roses. Fertilize every two weeks with a high phosphorus, 10-30-20 fertilizer. Control pests and diseases like slugs and mildew, which are drawn to the moist conditions dahlias require to grow. Stake new growth as needed.

Don’t expect to plant one dinner plate dahlia variety and cultivate a plant smothered in 10 inch blossoms. Most jumbo flowers are the result of pinching off all but one flower, resulting in a show-quality blossom. This practice, known as disbudding, allows the plant to direct all of its energy into the creation of one giant flower.

At the end of the growing season, you can dig and store your dahlia tubers, or let them perish if you wish to buy new tubers the following season.

Garden Design With Dahlias

With flower varieties that grow from 12 inches to four feet tall, the dahlia is a versatile flower for the landscape. Although the giant types with ten inch flowers are exciting, choose a tall variety with more moderate four to six-inch flowers for the cutting garden.

Dahlias stand out in a mixed sunny flower border, but you can create a traffic-stopping garden filled only with dahlias. Dahlias also look nice in summer garden containers, but the plants may not grow as large in containers.


With tens of thousands of varieties to choose from, how can we mere mortals choose the perfect specimen for our gardens? The American Dahlia Society eases our burden by publishing a list of the “Fabulous Fifty,” a selection of varieties that have won at least 50 blue awards that year.

Here’s a sampler to get you started:

  • April Dawn: Large lavender and white flowers
  • Bodacious: A dinner plate type with sunset colors
  • Jessie G: Purple ball variety
  • Mary Jo: Coral, semi-cactus type
  • Shea’s Rainbow: Variegated pink and yellow cactus