Perennial Solutions: Dahlia Go Go Series By Paul Pilon

The Go Go series is available in seven colors. Orange is pictured.

Here I go again, this month I'm featuring another perennial that is not fully hardy across much of the country. Why do I occasionally feature such plants? Well sometimes there are impressive plants that can be grown as perennials for some growers and all too often many of the great perennials for the South are overlooked. Bear with me as you read on and note that the dahlia market in other parts of the country is also alive and well.

The Go Go series of dahlia produces really large flowers with the blooms measuring 4-5 inches across. The series currently contains seven cultivars with a range of flower colorations. The cultivars are 'Go Go Blues', 'Go Go Orange', 'Go Go Peach', 'Go Go Purple', 'Go Go Speckled Pink', 'Go Go Two Tone' and 'Go Go White'.

Although, the Go Go series are great perennials in the landscape for some locations, many gardens utilize this dahlia series as an annual. The cold sensitive tubers can be lifted in the fall and replanted in the spring for those interested in doing so. Dahlias are commonly grown and marketed as patio containers.

Dahlias can be grown as perennials throughout USDA Hardiness Zones 8 to 10. They prefer locations with partial to full sun and grow 14-20 inches tall when they are in full bloom. The Go Go series blooms in the summer and continues flowering well into the fall; providing loads of color when most perennials have already finished blooming. The demand for dahlias is strong in both locations where they can be grown as perennials and in other parts of the country where they are utilized as annuals.

Propagation

The Go Go cultivars of dahlia are vegetatively propagated. Commercial growers use tubers as their starting materials. Therefore, it is not practical for growers to propagate this type of dahlia on their own.

Production

The Go Go series is well suited for production in large container sizes; eight to 12-inch pots are ideal. Many commercially available peat or bark based growing mixes work well, provided there is good water retention, yet adequate drainage. Plant one tuber per container with the top of the tuber being planted so the crown is at or no more than one-inch below the media surface. The crown is the portion of the tuber where the old stem meets the tuber. Improperly planting the tubers will lead to crop variability and potentially some losses. Avoid planting them too deeply or plant vigor will be reduced and crown and root rots are more likely to develop. Due to their cold hardiness, avoid planting them in the fall, dahlia should only be planted in the spring. Some growers apply broad spectrum fungicide drenches after potting; however, I find with good moisture management that fungicide applications are often not necessary.

The Go Go series requires above average amounts of irrigation. They prefer to be kept evening moist, but not consistently wet during production. Too much moisture can lead to the development of crown and root rots. As the crops mature, they will need to be watered more frequently. When irrigation is necessary, water them
thoroughly, then allow the soil to dry slightly between irrigations.

Dahlia are heavy feeders and require more fertilization than many perennials. Growers using water soluble fertilizers either feed with a constant liquid fertilization using rates of 150-ppm nitrogen with every irrigation or apply 300-ppm nitrogen as needed. Begin the fertilizer application once the new growth has begun. Controlled-release fertilizers can also be incorporated into the growing mix prior to planting using the medium recommended rate or the equivalent of providing approximately 1.2 pounds of elemental nitrogen per yard of growing mix. When topdressing controlled release fertilizers, use the medium rate and wait for the foliage to be present before applying the fertilizer. Maintain the pH between 6.5 and 7.0 throughout the production cycle.

Growers can elect to pinch dahlia or to leave them alone. Extensive trials at Ohio State University were conducted and the results showed that most Go Go cultivars only had a slight increase in the number of flowers produced after pinching. Additionally, pinched plants were actually slightly taller when in bloom compared with non-pinched ones. Additionally, plants that were pinched took two to four weeks longer to flower than plants that were not pinched plants. Therefore, pinching is not necessary or extremely beneficial. I recommend growers only pinch the plants that appear thin or misshaped, leaving two to three sets of leaves.

The Go Go cultivars produce a good sized plant. The stems are sturdy and growth regulators may not be necessary. However, the plants can be toned using spray applications with the tank mix of 2,500- to 3,750-ppm daminozide (B-Nine or Dazide) plus 1,000- to 1,250-ppm chlormequat chloride (Cycocel or Citadel). If more height control is desired drench applications of A-Rest are effective; apply 2-4 ppm in peat-based growing media and 4-8 ppm in bark mixes. PGR drenches should be applied early in production; apply when the shoots are emerging from the soil. Plant size can often be maintained by providing adequate space between the plants. Do not grow dahlia pot-to-pot; be sure to give them adequate room between the containers.

Insects and Diseases

Aphids, Japanese beetles, leafhoppers, slugs, two spotted spider mites, Western flower thrips and whiteflies can often be observed on or around dahlia crops. Of these pests, Western flower thrips are the most problematic since they can distort the leaves and vector viruses.

There are several diseases that affect the successful production of dahlia. The most problematic diseases (Erwinia, Pythium and Verticillium) attack the roots and/or tubers. Other pathogens which can be observed on occasion are Botrytis, leaf spots (Alternaria and Ascochyta) and powdery mildew.

Routine scouting is useful and recommended to detect insect pests and plant diseases early, allowing the appropriate control strategies to be implemented before significant crop injury or mortality occurs.

Temperature and Scheduling

The ideal temperatures for growing the dahlia Go Go series are 60¡ F at night and 75¡ F during the day.

Avoid growing them with temperatures below 50¡ F during the day or 40¡ F at night; temperatures this low are too cold for dahlias. The time to flower varies slightly from one Go Go cultivar to the next; however, most cultivars can be grown and in flower in eight to 10 weeks. Depending on the cultivar, it takes an additional 16-31 days to produce flowering containers when the plants have been pinched.

Availability

The dahlia Go Go series is being marketed by Growing Colors. Tubers are available from Garden World Inc. (www.gardenworldinc.com), Growing Colors (www.growingcolors.com) and 2Plant International (www.2plant.com). In Canada, they can be purchased from Paridon Horticultural Ltd. (www.paridon.com).

Perennial Solutions: Dahlia Go Go Series

Paul Pilon

Paul Pilon is a horticultural consultant, owner of Perennial Solutions Consulting (www.perennialsolutions.com), and author of Perennial Solutions: A Grower's Guide to Perennial Production. He can be reached at 616.366.8588 or paul@perennialsolutions.com.