Dahlia XXL Series


Dahlias have always been a dramatic addition to a garden or patio, but with the introduction of new RED FOX dahlia XXL, the curtain has opened on a whole new act. All seven XXL varieties are just as their name suggests — large-flowered dahlias with blooms boasting almost half a foot of diameter. What’s different, though, is that these tremendous flowers grow on a medium vigorous plant good for gallon production, which is controllable and keeps a suitable size for the garden through the summer. Dahlia XXL has been a strong performer in trials throughout North America over the summer of 2011. Texan and Georgian heat, Colorado’s high altitude, Ontario’s northern light —  XXL dahlias have performed beautifully in all conditions.

Here are guidelines on how to get the most from your the XXL dahlia series.


XXL dahlias root easily and quickly without the need for treatment with rooting hormones. For best results, root under long days of at least a 14-hour day length. To prevent stretch, spray applications of B-Nine or Dazide (daminozide) at 1,500 to 2,500 ppm may be used. This will also tone the liners. Heavy shade, low light and close spacing can cause stretch of liners. One might use strip trays, spacing the cuttings on the bench as well as limiting the rooting time to three to four weeks.

Potting and Growing

When time to transplant, start with a sterile and well-drained root medium with EC of 1.5. Root medium pH should be between 5.7 and 6.3. Water the liners in with a fertilizer solution.

Pinch the plants, leaving two nodes, 10 to 14 days after potting the liners. Liners can be pinched leaving two nodes at potting only if liners have not been hardened or stressed after rooting. Earlier pinching will reduce crop time.

Temperature and Light

For best results, dahlia XXL should be grown at 70° F day and 65° F night. As for light, grow under long days with a minimum day length of 14 hours. Night interruption lighting, from 10 p.m. to 2 a.m. can also be used. Dahlia XXL loves full sunlight. Low light will slow flowering and can cause stretch.


High fertility with a root medium (EC 2.0 to 2.5) using a complete fertilizer is perfect for dahlia XXL. Maintain a root medium pH of 5.7 to 6.3.


When plant growth reaches the sides of the pot, apply B-Nine or Dazide at 2,500 ppm. Additional applications may be made as needed every two weeks.

To reduce flower peduncle stretch and improve sales appeal, apply B-Nine of Dazide at 2,500 ppm right before the plants flower.


From the rooted liner stage, recommended scheduling is as follows: 

Of course, ranges in weeks are related to growing conditions. For Southern high light climates use the minimum weeks, and for Northern low light conditions use the maximum. Adjust for your specific greenhouse conditions and growing techniques.  

About The Author:

Paul Hammer is research and development manager and Brad Kunhardt is marketing team leader with Dümmen USA. For more information, email techservices@dummenusa.com.

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