November 2011 Culture

Helenium ‘Double Trouble’

Helenium is a very attractive, yet underutilized perennial. Helenium ‘Double Trouble’ is no exception, as it is the only commercially available double flowering cultivar, producing countless small, daisy-like double bright, yellow flowers on strong stems that bloom for a long time. It is one of the most attractive perennials for mid- to late-summer color in landscapes when few perennials are at their peak.

‘Double Trouble’ forms attractive, spreading clumps reaching 18 to 28 inches tall and sets the landscape ablaze in the mid summer with an abundance of flowers containing two to three rows of bright yellow petals surrounding  honey-yellow centers. It grows best in full to part sun in moist, but well-drained soils. Helenium are hardy throughout USDA Hardiness Zones 4 to 8. Helen’s flower (named in honor of Helen of Troy) is used to brighten borders, as accent plants, in mass plantings, patio containers and for cut flowers. Additionally, they are resistant to deer feeding and attract butterflies into the landscape. 

‘Double Trouble’ is a unique cultivar selected by the ongoing helenium breeding efforts of Pieter Damen at his nursery in Hillegom, The Netherlands. It is an eye-catching perennial that is sure to get everyone’s attention with its cheerful display of bright-yellow, double flowers. It is a superb, all around perennial that produces masses of blooms over an exceptionally long period. With these characteristics, compact habit, sturdy stems, and ease of production, helenium ‘Double Trouble’ is a great candidate for late summer programs.

Propagation

Helenium ‘Double Trouble’ is vegetatively propagated by tip cuttings by a limited number of licensed propagators and self-propagation is strictly prohibited. Licensed propagators root tip cuttings by sticking them directly into a pre-moistened, well-drained growing medium in liner trays with medium (105 to 72) cell sizes.  

Place the cuttings under low misting regimes for about the first six to 10 days of propagation. When possible, it is usually best to propagate under high humidity levels (90 percent relative humidity) with minimum misting. The misting and the humidity levels can gradually be reduced as the cuttings form callus and develop roots. At seven to 10 days after sticking, it is beneficial to apply water-soluble fertilizers using 75- to 100-ppm nitrogen at each irrigation. 

Remove the cuttings from the mist once they are rooted; the cuttings are usually rooted in less than three weeks with soil temperatures ranging from 68 to 74° F. Liners take approximately five to seven weeks from sticking to become fully rooted and ready for transplanting.  

Production

Helenium ‘Double Trouble’ is well suited for production in one gallon or larger sized containers. For best performance, plant one plug liner into each 1-gallon pot filled with a good quality, well-drained peat- or bark-based growing medium. When transplanting the liners, plant them even with the soil line of the plug it was previously produced in.  

Helen’s flower requires an average amount of water. When irrigation is necessary, water them thoroughly then allow the soil to dry slightly between irrigations. Once they are established and growing rapidly, they will require more frequent irrigations.

They are moderate feeders. Helenium perform best when either a constant liquid fertilization program is used feeding at rates of 75 to 150 ppm or using higher rates of 150 to 200 ppm as needed. Fertility can also be delivered using controlled-release fertilizers by topdressing the media surface using the medium rate listed on the product’s label, or incorporating them into the growing medium prior to planting at a rate equivalent to 1 to 1.25 pounds of nitrogen per cubic yard of growing medium. The pH of the media should be maintained between 5.6 and 6.4.  

Under certain growing conditions or when grown at high plant densities, it may be necessary to use plant growth regulators to reduce stem elongation and produce a high quality product. Plant stretch can often be reduced by providing adequate spacing between the plants. In the northern parts of the country, spray applications of daminozide (B-Nine or Dazide) at 2,500 ppm are effective (higher application rates may be necessary in southern locations). Applying one to two applications seven days apart should provide adequate height control.  

Insects and Diseases

Although helenium can be produced relatively insect free, aphids, leafhoppers and spider mites can often be observed feeding on them. All of these pests can be detected with routine crop monitoring; control strategies may not be necessary unless the scouting activities indicate actions should be taken.  

The most common diseases are fungal leaf spots, powdery mildew, root rots and rust. Of these diseases, powdery mildew is the most prevalent. The occurrence of powdery mildew can be reduced with managing the environment by providing the proper plant spacing, adequate air movement, and controlling the humidity, or if desired, following a preventative spray program using the appropriate chemicals.  Azoxystrobin, kresoxim-methyl, myclobutanil, pyraclostrobin + boscalid, trifloxystrobin and triflumizole are all effective products to rotate between in preventative programs.  

Forcing

Most growers grow helenium ‘Double Trouble’ for early to mid summer sales. It does not have a cold requirement for flowering and can be easily produced for sales the same year it was started. To promote branching and fullness, many growers pinch them a couple of weeks after transplanting.

Helenium has an obligate long day requirement for flowering. They will not flower when grown under short day lengths. In fact, they will stay compact and rosette when the days are extremely short. If early flowering is desired, it is recommended to provide at least 14-hour photoperiods or night interruption lighting when the natural day lengths are less than 14 hours. The amount of time to produce blooming plants after the proper photoperiod is provided is a function of temperature. ‘Double Trouble’ takes nine to 11 weeks to flower when it is grown at 66 to 72° F.

Availability

Helenium ‘Double Trouble’ is brought to the marketplace by Darwin Plants (www.darwinplants.com). Rooted liners are available from the Ball Horticultural Company (www.ballhort.com) and several of their perennial propagators.