January 2009 Culture

Aubretia hybrida Axcent series By Paul Pilon

Growers looking for easy-to-grow, early-spring-flowering perennials should be interested in the Axcent series of aubretia from Syngenta Flowers. Compared to other cultivars on the market, the Axcent series blooms one to two weeks earlier and provides an extended shelf life as it blooms for up to eight weeks. With its flower power and early bloom, it can easily be marketed alongside annuals in the early spring.

The series consists of six colors: Antique Rose, Blue with Eye, Deep Purple, Lilac, Magenta and Violet with Eye. These cultivars produce an impressive display of large 3Ú4- to 1-inch blooms which completely covers the entire plant. The compact mounds of color reach 4-6 inches tall and 12-14 inches wide at maturity. This cool-season perennial is suitable for production in USDA Hardiness Zones 4 to 9 and AHS Heat Zones 8 to 1. It performs best when grown in sunny locations in the North and under partial shade when produced in the South.

Aubretia is commonly used in containers, patio pots, and in small mass or border plantings. With its container and garden performance, ease of production and flower power, the Axcent series is an impressive and reliable performer which will complement any commercial perennial program.

Propagation

The Axcent cultivars are vegetatively propagated from tip cuttings by licensed propagators. A U.S. Plant Patent has been applied for (USPPAF); propagation without permission of the applicant is illegal. Before sticking the unrooted cuttings (URCs), moisten the rooting medium in the plug flat. Rooting compounds are optional as aubretia will root well without using them.

Place the cuttings under a low misting regime for the first seven to 10 days of propagation. When possible, it is usually best to propagate under high humidity levels (90 percent relative humidity) with minimal misting. At seven to 10 days after sticking, it is beneficial to apply water-soluble fertilizers using 75- to 100-ppm nitrogen at the beginning of each irrigation. The misting can gradually be reduced as the cuttings form callus and root primordia. 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 64-68¼ F. Liners take approximately five to seven weeks from sticking to become fully rooted and ready for transplanting.

Production

The Axcent series is most commonly produced in small container sizes (5-inch or smaller) with a single plug planted in the center of the pot. When transplanting, the growing medium of the pot should be even with the top of the plug. Aubretia performs best when grown in a slightly dry to moist, well-drained medium with a slightly acidic pH: 5.5-6.5. When irrigation is necessary, water them thoroughly, then allow the soil to dry slightly between irrigations.

They are moderate feeders. Providing high or luxury fertility levels will cause them to appear lush and may delay flowering. Nutrients are commonly delivered using water-soluble sources, providing 75-100 ppm using a constant liquid fertilizer program or 150 ppm as needed. Several growers incorporate low rates of controlled-release fertilizers into the growing mix before planting to effectively provide nutrients to containerized aubretia.

With the compact growth habit of the Axcent series, it is usually not necessary to control plant height. However, under certain circumstances, such as when they are grown at high plant densities or with "luxury" nutrient levels, it may be necessary to implement height-management strategies. If production space is available, provide adequate space between plants to reduce stem elongation. Under some conditions, it may be necessary to use chemical plant growth regulators to control the growth of Myosotis. If PGRs are necessary, it is recommended that growers apply daminozide (B-Nine or Dazide) at 2,500 ppm or the tank mix of daminozide at 2,000 ppm + chlormequat chloride (Citadel or Cycocel) at 1,000 ppm. One or two applications of plant growth regulators applied seven days apart should provide adequate height control.

Insects and Diseases

Although aubretia can be produced relatively free of diseases and insects, growers frequently observe aphids and Pythium during production.

Several growers implement proactive aphid control strategies using drench or spray applications of systemic chemicals containing the active ingredients acetamiprid, dinotefuran, imidacloprid, py-metrozine or thiamethoxam. The occurrence of Pythium is most prevalent under cool and wet growing conditions, and also frequently arises where the salt levels are too high (greater than 2.5 mmhos/cm using the saturated media testing method). Insects and diseases can be detected with routine crop monitoring; control strategies may not be necessary unless the scouting activities indicate actions should be taken.

Forcing

The Axcent series is easy to force into bloom and is most commonly produced for early spring sales. They have an obligate cold requirement for flowering. Aubretia can be vernalized in the final container or as large plugs (72-cell or larger) for a minimum of six to eight weeks at 35-44¡ F. Following the cold treatment, they will flower under any photoperiod (day neutral plants) and can be forced into bloom under natural day lengths. The length of the photoperiod does not have any effect on the time to flower or the number of blooms produced.

There are two common approaches to producing flowering containers of aubretia. The first method entails planting unvernalized plugs into the final container during early to mid-fall. Allow them to bulk up slightly, vernalize them, and force them to bloom in the early spring using low production temperatures of 60-65¼ F for six to eight weeks. The second strategy involves transplanting vernalized plugs into the final containers during the late winter and forcing them at 60-65¼ F for six to eight weeks. For a fuller appearance, I recommend bulking them in the fall before they are to be sold the following spring.

Availability

Unrooted cuttings of aubretia Axcent cultivars are available to growers through Syngenta Flowers (www.syngenta flowersinc.com). Plugs can be acquired from Pacific Plug and Liner (www.ppandl.com) and many reputable perennial plug producers or plant brokers.