, all of which resulted in higher SPAD readings than the no N treatment. Fig. 2. Effect of N rate on leaf SPAD reading ( A ) and leaf area ( B ) of Hydrangea macrophylla ‘Merritt’s Supreme’ on 27 Oct. Hydrangea plants were fertilized with 0, 5, 10, 15
Tongyin Li, Guihong Bi, Richard L. Harkess, Geoffrey C. Denny, and Carolyn Scagel
Guihong Bi, Carolyn F. Scagel, and Richard Harkess
without causing nutrient deficiency or reducing plant quality. Materials and Methods Plant culture, nitrogen treatments, and sampling. Rooted Hydrangea macrophylla ‘Merritt's Supreme’ cuttings were potted into Elite/Ultra Azalea pots (17
Guihong Bi and Carolyn F. Scagel
defoliation removes green leaves from plants before any significant N mobilization occurs. In Hydrangea macrophylla ‘Merritt's Supreme’, ≈50% of total plant N was in leaves in early fall ( Bi et al., 2008 ). Early defoliation could potentially decrease N
Theo J. Blom and Richard B. Smith
Summer-grown Hydrangea macrophylla subsp. macrophylla var. macrophylla (Thunb.) were exposed for 1 week to CzH4 at 0,0.5,2.0,5.0,50, or 500 μl·liter-1 in dark storage at 16C for defoliation before cold storage. The number of leaves remaining per shoot for all cultivars decreased with C2H4 concentration, and >5 μl C2H4/liter was effective in defoliating `Kasteln', `Mathilda Gutges', and `Todi' but not `Merritt's Supreme'.
Youping Sun, Guihong Bi, Genhua Niu, and Christina Perez
’ hardy hydrangea ( Cochran et al., 2013 ). Both hydrangea cultivars set flower buds on current season wood. However, ‘Merritt’s Supreme’ bigleaf hydrangea produces blooms on old wood. Therefore, the timing of foliar application and dosage of dikegulac
R.I. Wilkinson and B. Hanger
Miniature flowering potted Hydrangea macrophylla Thunb. cv. Merritt's Supreme plants (multistem, 15 to 20 cm tall) were grown in a modified hydroponic system. High-quality plants were produced by pulsing plants with paclobutrazol (0.2 mg·liter-1) for 4 weeks. Flower initiation was advanced in the terminal buds of treated plants by 12 days, and this earlier flower development was maintained through to flower maturity, without loss of inflorescence diameter. Chemical name used: β -[(4-chlorophenyl) methyl] -α-(1,1-dimethylethyl)-1 H -1,2,4-triazole-1-ethanol (paclobutrazol, ICI-PP333).
Douglas A. Bailey and Bernadette Clark
Summer spray applications of 5000 ppm daminozide (1× or 2×), 62 ppm paclobutrazol (1× or 2×), or 5 ppm uniconazole (1× or 2×) were applied to seven cultivars (Böttstein, Enziandom, Kasteln, Mathilde Gütges, Merritt's Supreme, Red Star, and Schenkenburg) of florists' hydrangea [Hydrangea macrophylla subsp. macrophylla var. macrophylla (Thunb.) Ser.] to evaluate cultivar response to plant growth retardants (PGRs). Both daminozide treatments and the 2× uniconazole treatment effectively reduced plant height for all cultivars during the summer growth period; cultivars varied in response to the paclobutrazol treatments and the 1× uniconazole treatment. Daminozide and uniconazole treatments resulted in less elongation than all other treatments during forcing for most cultivars tested. Paclobutrazol treatments had no residual effect on shoot elongation during forcing of the cultivars tested. The 2× treatments of all PGRs decreased inflorescence diameter of some of the cultivars tested compared with nonsprayed controls. Results from this study indicate that 1) summer application of PGRs can have a residual effect on plant height and inflorescence diameter of hydrangeas during the spring greenhouse forcing phase; and 2) hydrangea cultivars differ significantly in response to the PGRs tested. Therefore, the need for height control during the spring forcing period of hydrangeas will vary with cultivar, and it will depend on how plants were treated the previous summer growing season. We recommend that producers of dormant hydrangeas provide records of their summer height control program to forcers so that height control programs during spring forcing can be adjusted appropriately.
Keri D. Jones, Sandra M. Reed, and Timothy A. Rinehart
Lacecap’. Stainable pollen for the triploid H. macrophylla ssp. macrophylla cultivars averaged 63% and ranged from 25% in ‘Masja’ to 85% in ‘Marechal Foch’. Less than 50% stainable pollen was also observed in the triploids ‘Merritt's Supreme’ and ‘Todi
Youping Sun, Genhua Niu, Haijie Dou, Christina Perez, and Lisa Alexander
× macrophylla ‘Sabrina’ and ‘Selina’ were relatively salt-tolerant; H. macrophylla ‘Merritt’s Supreme’ and ‘Mathilda’ were moderately tolerant, Hydrangea quercifolia ‘Snowflake’ and H. macrophylla ‘Emotion’ were moderately salt sensitive; and H
Diana R. Cochran, Amy Fulcher, and Guihong Bi
of daminozide increased inflorescence size of ‘Schenkenburg’ florist hydrangea, but had no effect on six other florist hydrangea cultivars (Böttstein, Enziandom, Kasteln, Mathilde Cütges, Merritt’s Supreme, and Red Star). Norcini et al. (1994