Growing Dahlias

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Dahlias are perennial flowers that come in various shapes, sizes and colors. These flowers thrive in cool and moist climates which make them perfect for us Pacific Northwesters to grow! However, many struggle with growing these plants into blooming beds of rich color and then turn away from trying to grow them ever again.

Here are TIPS that’ll make you rethink twice about how difficult it is to grow dahlias.

 Preparation for  Planting

  • Soil temperature should be at 60 degrees.
  • Location of planting should receive full sun ( 6 to 8 hours of sunlight)
  • PH level of your soil should be 6.5- 7.0 and slightly acidic. Dahlias grow better in rich, well- drained soil.


  • When planting the dahlia tubes, make sure the hole in the soil is slightly larger than the root ball of the tube with some compost or peat moss into the soil.
  • Plant the tubes 9 to 12 inches apart. For small flowering types, space two feet apart and for tall, large flowering types, space three feet apart when planting.
  • Plant tubes that have a little bit of green growth instead of ones that appear to be wrinkled or rotten.
  • Do NOT cut or break individual tubes as you would with potatoes and plant them WHOLE.
  • Plant them with the growing points, or ‘eyes’ pointing up and about 6 to 8 inches deep.
  • Do NOT water right after planting since this encourages rot to happen. Instead, water when you notice sprouts have appeared above the soil.
  • Do NOT cover with mulch or bark which can challenge sprouting to happen.
  • Blooming will start to occur about eight weeks after planting.


  • Do NOT fertilize at planting.
  • Use a fertilizer that is low in nitrogen (5-10-10 or 10-20-20 are recommended).
  • Apply fertilizer when plants begin sprouting and then every three to four week from mid- summer to early Autumn.


  • Do NOT water the soil until the Dahlia plants appear.
  • Do NOT over water which can cause the tubes to rot.
  • Once plants are established, do a deep watering two to three times a week for at least 30 minutes ( a little longer during warmer climates).


  • To achieve nice stems for cutting: compact plants, pinch out the center shoot above the third set of leaves.
  • To get the most out of your cut flowers, place them in very hot water (160 degrees F) and leave it in there until it cools down.

After Season Care

  • Foliage blackens when the first frost happens.
  • In zone 8, dahlias can be cut back and left in the ground during winter but cover with a deep, dry mulch.
  • In other areas, the tubes should be taken out of the ground. Wait a few days after the foliage blackens to remove from the soil.


Still think Dahlia’s are difficult to grow? 

Come to our DAHLIAS SEMINAR on JUNE 7 at 11 A.M. to learn from a MASTER GARDNER on how to be successful with this flower!



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