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A Guide to growing Dahlias

Dahlias can be tricky. 

We have tried to "crack the code" for you and created

this guide to help you grow your dahlias with ease.  

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Site and soil preparation

  • Chose a bright sunny spot that will get an average of 7 to 8 hours of sunlight.  

  • Dahlias require good drainage.  Loosely amend the soil 18” wide by 18” deep.  

  • If you are amending with store bought soil, avoid those that contain chemical fertilizers and/or fresh manure that can be caustic to your tubers.  

 

 

Protection

  • Gophers like dahlias: If you are planting directly in the ground, protect your tuber with a gopher cage or cage formed with 1/2” hardware cloth.

  • Dahlias do well in both pots and raised beds, but will require increased watering during the growing season.

 

 

When will my dahlias sprout?

  • Dahlias are all different. Some dahlias can take up to 6+ weeks to sprout! 

  • Plan to plant your dahlias when soil temperatures are above 60 degrees.

  • Avoid planting if there is either prolonged rain or high temperatures forecasted.

 

 

What do I do if my dahlia has sprouted? (Hardening off)

  • If your tuber has any sprouting or leaf development, it is likely not ready to be planted directly in its final growing location or exposed to full sun.  

  • If your tuber has 1-2” of sprouting, you can plant directly as described below (“Planting and Staking”) and gently backfill the entire sprout with soil.  

  • Dahlias with sprouting greater than 3-4" should be planted in a pot first and slowly hardened off. Position the tuber so the sprout is facing upward.  

  • Do not water your dahlia until a set of true leaves has formed.

  • After hardening off your dahlia, carefully transplant it to its final growing location on a cool day to avoid transplant shock.  

 

 

Planting and staking

  • For the home gardener, dahlias should be planted approximately 4" deep and 24” apart to allow for ample air circulation which helps decrease the risk of disease.

  • Place the tuber side-lying with any visible “eyes” or sprouting face up.  

  • Before back-filling with soil, spike a 3+ foot stake a few inches away from the tuber.

 

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Watering

  • DO NOT WATER YOUR SOIL OR DAHLIA until you have visible signs of a green leaves! This includes protecting your dahlia from rain. 

  • Once leaves have developed, water deeply 2x to 3x a week at soil level.   

  • Avoid overhead watering.

 

 

Pinching

  • When your dahlia has reached a height of about 12”, pinch the center stalk to promote side branching.

  • As your plant matures to about 3 feet in height, pinch off the bottom 2 to 3 sets of leaves to improve air circulation.

  • Use twine or string to tie your dahlia securely to the stake as it grows.

 

 

Feeding

  • Dahlias are heavy feeders.  Feed monthly with a “Bud & Bloom” fertilizer that can be gently worked and watered into the soil.

  • Supplement with foliar feeding when temperatures are around 70F, ideally early morning or dusk to avoid leaf burn.

 

 

Prevention & treatments for common diseases/pests: 

  • Many common diseases can be avoided by proper feeding and watering. 

  • Companion planting:  Nearby plantings of mint, basil, or fennel/dill can attract beneficial insects to control “enemy” insects

  • Leaf miner:  Remove infected leaves.  Spray with neem oil.

  • Powdery mildew:  Remove infected leaves. Spray with baking soda solution, neem oil, or Copper Fungicide.

  • Snails/slugs:  Sprinkle the perimeter of your planting area with diatomaceous earth or Sluggo Plus.

 

 

ENJOY!   Dahlias make excellent cut flowers!!  

  • Fill a bucket with tepid water about 4”+ deep. 

  • Harvest dahlias in the early morning when they are 75% developed/open.

  • Using clean and sharp snips, cut stems at an angle and place directly into water.

  • Allow dahlias to rest and hydrate in a cool dark place for several hours prior to use.

  • To maximize vase life, use floral food or a floral preservative.

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