Caladiums can be excessively large relative to the container in which they are grown, and plant growth regulators (PGRs) are required for height control. No industry standard has been set for optimal height of caladiums, but plants 25 to 28 cm tall (excluding the pot) would be considered commercially acceptable (Barrett et al., 1995). Paclobutrazol (Bonzi; Syngenta, Greensboro, N.C.) substrate drench recommendations vary from 8 mg·L−1 (Dole and Wilkins, 2005), 0.5 to 1 mg/pot a.i. (Barrett et al., 1995), or 3 to 4 mg/pot a.i. (Wilfret, 1993). All drenches are applied when new growth emerges through the top of the substrate. Wilfret (1993) reported substrate drenches of uniconazole (Sumagic; Valent USA, Marysville, Ohio) at 1 to 2 mg/pot a.i. also were effective. Dole and Wilkins (2005) recommend foliar sprays of daminozide (B-Nine; Chemtura Corp., Middlebury, Conn.) at 2500 mg·L−1, applied up to three times, at 5- to 7-d intervals beginning after the leaves have emerged and fully expanded.
Preplant bulb PGR soaks have been shown to be an effective method of controlling height in a number of other bulb crops, including hyacinths, lilies, narcissus, and tulips (Krug et al., 2005a, 2005b, 2005c, 2006). Preplant tuber soaks of paclobutrazol or uniconazole at a concentration of 5 mg·L−1 on de-eyed tubers were shown to retard overall foliage height (Wilfret, 1993). Flurprimidol (Topflor; SePRO Corp., Carmel, Ind.) has been available in Europe for more than 20 years as a 1.5% formulation and is being introduced into the U.S. market as a 0.38% formulation, but commercial dose recommendations for caladiums are not available. Therefore, this study was conducted to determine the efficacy of flurprimidol preplant tuber soaks and substrate drenches on caladiums.
Krug, B.A., Whipker, B.E. & McCall, I. 2005a Flurprimidol is effective at controlling height of ‘Star Gazer’ oriental lily HortTechnology 15 373 376
Krug, B.A., Whipker, B.E., McCall, I. & Dole, J.M. 2005b Comparison of flurprimidol to ethephon, paclobutrazol, and uniconazole for hyacinth height control HortTechnology 15 1 3
Krug, B.A., Whipker, B.E., McCall, I. & Dole, J.M. 2005c Comparison of flurprimdiol to ancymidol, paclobutrazol, uniconazole for tulip height control HortTechnology 15 370 373
Whipker, B.E. & Hammer, P.A. 1997 Efficacy of ancymidol, paclobutrazol, and uniconazole on growth of tuberous-rooted dahlias HortTechnology 7 269 272