CREATING A POTTED, FLOWERING HEDYCHIUM WITH GROWTH RETARDANTS

Abstract

A 1 to 2 meter tall rhizomatous herb, the Hedychium gingers find use in the landscape for their fragrance, but are too tall for potted plant use. Experiments using growth retardants were designed to determine effective concentrations to control plant size for potted plant production. Rhizome divisions of Hedychium coronarium (J.G. Koenig) var. maximum (Roscoe) were drenched with 0, 50 or 100 mg·L -1 paclobutrazol (PBZ) while in the propagation flats and 4 weeks after potting into 20 cm pots with 0, 50 or 100 mg PBZ per pot. Inflorescence-bearing stalks of controls were tallest, averaging 135.5 cm, while plants that received the double treatments were 36.7 and 43.7 cm tall for the 50 and 100 mg PBZ concentrations. Plants that were drenched after potting up were shorter than plants that received PBZ during the propagation phase, showing that the second drench had a greater effect than did the drench in the propagation flat. In a second experiment, hybrid Hedychium rhizomes bearing one leafy stalk were drenched with PBZ or uniconazole (UNI) at the rates of 12.5, 25, or 50 mg per 20 cm container. Flowering stalks of controls averaged 82.5 cm. Increasing PBZ and UNI concentrations retarded stalk lengths with UNI having a greater effect than PBZ, but PBZ-treated plants were better proportioned at 27 to 32 cm than were UNI-treated plants at 11 to15 cm. Fewer flowering stalks developed in the 25 and 50 mg PBZ treatments than with 12.5 PBZ, while plants treated with UNI were about equally productive and equivalent to PBZ at 12.5 mg per pot. Leaf counts on the stalks ranged from 8.5 in the 50 mg PBZ treatment to 11.5 for the control, with most in the 10 – 11 range, suggesting that the retardants had little effect on floral initiation of potted plants. The fragrant, pastel hybrid Hedychium selections make attractive potted plants. Since Hedychium can be timed with long daylengths, year-around production is possible.