Gardening 101: Growing Dahlias

Click on dahlia icon for information about the upcoming American Dahlia Society National Show (September 9/10).

Click on dahlia icon for information about the upcoming American Dahlia Society National Show (September 9/10).

Dahlias are the exuberance of a fall garden. Planted in mid-April then mostly forgotten, they show up and show off when the borders and the gardener need a boost. Mixed with other fall bloomers like sneezeweed, mountain mint, gaura, Joe Pye weed, rudbeckia, and anemones, dahlias take ordinary borders and make them extraordinary. And, they're pretty much pest and trouble free. (Jury is mixed on whether they serve as deer food. Please share your experience below). 

Rudbeckia subtomentosa 'Henry Eilers' is a perfect combination plant with dahlias for late summer bloom. It gets tall, 3'-5' x 1'-2'. If that's too tall, there is 'Little Henry' that maxes out at 3'-4' feet. Worth the trouble of staking or using flower supports. The taller dahlias will need support, too. I highly recommend the easy-to-use half circle flower supports we carry at the store.


Types of Dahlias

For a description of each type of dahlia, click on this quick read from American Dahlia Society. Listed below are the more recognizable forms of dahlias.  

  • Anemone
  • Ball or Pom Pom
  • Border
  • Catcus and Semi-catcus
  • Decorative
  • Dinnerplate
  • Mignon
  • Waterlily

Growing Dahlias: How-To

Dahlias are hardy in zones 8-10. BB Barns sells dahlia tubers in spring. Dahlias are not part of your fall bulb planting (which we'll discuss in another post). They are considered a tender perennial, or summer bulb. The tubers look like potato tubers except dahlias only have eyes at the stem end of the tuber.

Sneezeweed, Helenium 'Helbro' Mardi Gras with catcus dahlia in background. This sneezeweed or sometimes called Helen's flower begins blooming in early June and continues until mid-to-late October depending on the temperatures. It's a great summer-to-fall perennial and good combination with dahlias. This one 'Mardi Gras' gets 3'-4' x 2'-3' feet. There are shorter cultivars, like  'Short and Sassy' that top out at 18". 

  • Plant dahlias in mid-April to early May, when the soil and air temperatures are warmer (60°).
  • Plant new tubers 1-2" deep with 1" of soil covering the sprouting tip.
  • Plant in full sun with good drainage, and a pH of 6.5-7.
  • Plant taller varieties outside of windy areas and where providing support will be easy. Use flower rings, stakes or plant near fences where stems can lean or be tied. 
  • Fertilize with a low nitrogen fertilizer (5-10-10) a month after planting, then monthly after that. Do not overfeed. 
  • Dig up in the fall. Dahlias are native to Mexico and Central America and while they will survive a mild winter here, they won't survive a harsh one. Dig up gently with a pitch fork and shake all the soil loose. Store in newspaper, sawdust or peat moss in a dry place for the winter. Douse with a bit of water once a month to avoid shriveling. 

Maintaining Dahlias: Trouble Shooting

  • Don't over-water. Like bulbs, the tubers need good drainage. Over-watering and poor drainage can cause bacterial or fungal problems in the soil. If the plant wilts, dig it up and discard the entire plant.  
  • Borers and aphids are sometimes a problem. For aphids, Neem works well. For borers, cut off infected stems and destroy. 
  • Always keep dahlias weeded, they don't like competition

More Information: Links

If you'd like more information regarding dahlias, check out the links below.

Pretty Pics

Thank you to Poppins Possies in Mills River for these dahlia pictures. They allowed me to stomp around their cut flower farm, which is presently loaded with dahlias, taking pictures one afternoon. (My job is the worst. :) These are definitely a feast for sore eyes. Click on each picture for the slideshow. I'm gonna bet that next spring, you'll be in the store buying dahlia tubers after scrolling through these. Enjoy!


Written by Cinthia Milner, garden coach, blog writer, outside sales staff.

BB Barns serves all of Western North Carolina, upstate South Carolina and Tennessee.