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Dahlia Instructions

During the last sixteen years, Mark Harvey has lived and breathed dahlias. He enjoys sharing growing tips and planting strategies with his neighbors and clients, and encourages you to call with any questions you might have about helping your dahlias thrive.

Dahlia Planting Instructions

All my techniques are done as natural as possible. You will do just fine using natural or organic products like manure, plant rotation or even slug smashing. You can use pesticides on dahlias, but I would personally rather see a bug on my flower vase than have chemicals radiating a hole in my dining room table.

Where to plant:

  • Full sun to half of sun / day
  • Well-drained soil – too wet they can rot
  • Plant so dahlias are not competing with other plants; give plants at least 2 feet of space
  • Plant May to June 1st unless you live in places that warm earlier in the year, then plant earlier (soil must be consistent 60 degrees)
  • If climate is average 90 to 100 degrees, plant so they get a half day of morning sun


  • Plant dahlias on their side
  • If growth has started, cut back so only one inch of growth is connected to tuber (this will help the growth get through the soil)
  • Add a handful of bone meal and mix it in the hole
  • Plant tuber 4 to 6 inches deep


  • Use a low nitrogen fertilizer
  • You can also use natural fertilizers like steer, horse, cow and chicken manure if composted
  • Place 3 inches of fertilizer around top of soil


  • Slugs are the worst pests for your dahlia; you can use slug bait
  • They make organic slug bait, but you can also squash them
  • Spider mites can turn your leaves yellow and then brown throughout the plant
  • Keep your plant healthy by watering it during the dry part of summer; when plants are streed by dehydration spider mites will attach
  • Treat spider mites with neem oil; warm oil and then spray undersides of leaves
  • Mildew will not kill your plants but tends to occur in the fall when dahlias are past their prime; water the dahlia to suffocate the mildew

Do Not:

  • Water before your dahlias sprout
  • Use grass fertilizer
  • Use compost, which can be high in nitrogen
  • Spray for weeds around dahlias
  • Leave in ground in winter if your soil freezes 6″ or deeper

Check out the videos below with mark explaining how to get the most out of your dahlias

Planting Dahlias from Mark Harvey on Vimeo

Dahlia Cuttings from Mark Harvey on Vimeo

Dead Heading from Old House Dahlias on Vimeo

Mowing the Pretty Flowers Down Before Root Harvest from Old House Dahlias on Vimeo

Checking your Dahlia Tubers for Rot by Old House Dahlias on Vimeo