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Abstract
Stems of many woody ornamental plant taxa were collected in midwinter and hardened to their maximum capability under laboratory conditions. Hardiness levels were determined and compared to zone recommendations as listed in Hortus III and Rehder’s Manual of Cultivated Plants. Many woody plants had a greater midwinter cold tolerance than their hardiness ratings would infer.
Floral induction of 10 Hydrangea macrophylla (Thunb.) Ser. cultivars (`All Summer Beauty', `Dooley', `Endless Summer', `Générale Vicomtesse de Vibraye', `Lilacina', `Mariesii Variegata', `Mme. Emile Mouillère', `Nikko Blue', `Penny Mac', and `Veitchii') was evaluated to determine the remontant flowering potential. Cultivars exhibiting superior flowering potential could facilitate year-round production of florist s hydrangea and expand the geographic adaptation of hydrangeas in the landscape. Plants were tested under either 8-hour inductive short-day (SD) or 24-hour noninductive extended-day (ED) photoperiods at 24 ± 2 °C. Floral induction of H. macrophylla occurred under both SD and ED but was more rapid under SD than under ED. Shoot length and total number of nodes were significantly different for cultivars, photoperiods, and harvest dates. Significant differences in the floral initiation and development were observed among cultivars. `Penny Mac', `Endless Summer', `Lilacina', `Mme. Emile Mouillère', and `Nikko Blue' displayed significantly greater floral meristem development under SD than all other cultivars. Over the nine-week period, only `Dooley', `Endless Summer', and `Penny Mac' floral development was affected significantly greater by SD photoperiods than ED photoperiods. All others cultivars showed similar floral development under SD and ED. Stage of meristem development was highly correlated with number of nodes, but not with shoot length.
Abstract
Timing and rate of acclimation and maximum low-temperature survival of eight woody taxa were determined over six sample dates from 25 Aug. 1987 to 25 Apr. 1988. Four cultivars of Acer rubrum L. (red maple) acclimated at different rates and attained different levels of midwinter cold hardiness. ‘Red Sunset’ (RS) and ‘October Glory’ (OG), northern selections, acclimated at faster rates and attained greater degrees of cold hardiness than ‘Journalism Psychology’ (JP) and ‘Upright Crown’ (UC) selected from southern seed sources. Maximum cold hardiness levels were −8C (JP), −23C (UC), −29C (RS), and −29C (OG). Amelanchier arborea (Michx. f.) Fern, (downy serviceberry) and Quercus coccinea Muenchh. (scarlet oak) developed midwinter hardiness of less than −29C and −20C, respectively. Illicium floridanum Ellis (Florida anise) and Illicium parviflorum Michx. (small anise) developed −26C and −20C midwinter hardiness, respectively. According to our data, woody taxa should be evaluated for timing and rates of acclimation and low-temperature tolerances, since performance will vary from one geographic area to another, depending on photoperiod, the timing of fall freezes, and midwinter temperatures.
Abstract
Acer rubrum L. ‘October Glory’ cuttings taken on 15 June 1984 were subjected to short-day (SDT) or short-day plus night interruption treatments (NIT) from 25 July until 22 Oct. 1984. Additional cuttings taken on 14 Aug. were subjected to the same photoperiod treatments from 10 Sept. until 22 Oct. The height of the 15 June NIT cuttings was 50 cm greater than that of the 15 June SDT cuttings at the start of the first growing season, but no significant difference in height or caliper existed after two growing seasons of container culture. The greater growth rate of the 15 June SDT cuttings compared to 15 June NIT cuttings is attributed to their greater percentage of root carbohydrate reserves at the start of the first growing season. The initial root carbohydrate reserves and the final height and caliper of the SDT and NIT 14 Aug. cuttings were not significantly different. The 14 Aug. cutting growth results approached those of the 15 June cuttings. This indicated the growth potential of cuttings taken later in the season.
Abstract
Leyland cypress [× Cupressocyparis leylandii (A. B. Jacks.) M. L. Green] stem cuttings were collected in early March and treated with concentrated solutions of indolebutyric acid (IBA) or IBA plus boron. Nontreated cuttings rooted in low percentages producing one or 2 roots. IBA-treated cuttings rooted 90% with best rooting occurring at 0.8 and 1.6% levels. The 1.6 and 3.2% treatments resulted in foliar necrosis, and the cuttings continued to decline after transplanting. Boron had no positive effects on rooting. For best rooting a range of 0.3 to 0.8% IBA-concentrated dip is recommended.
Abstract
Inflorescence explants of Liriope muscari Bailey ‘ Variegata’ and Ophiopogon jaburan Lodd. ‘Variegatus’ produced multiple shoots in vitro on a modified Murashige and Skoog medium via callus. In subsequent studies with L. muscari‘ Variegata’, there was no difference in floret and scape explant growth, while rhizome and modified root explants were either contaminated or failed to grow. Distal floret explants produced more shoots than proximal explants but there were no significant positional differences in scape explants. In liquid culture 2,4-dichlorophenoxyacetic acid (2,4-D) at 0.5 mg/liter promoted the greatest fresh weight and shoot and root length. Benzylamino purine (BA) at 0.1 mg/liter increased the number of shoots while decreasing the number of roots. Agitation of liquid cultures increased callus fresh weight.
Fifty-four taxa of Atlantic white cedar [Chamaecyparis thyoides (L.) B.S.P.] were assembled and maintained. A protocol for propagation of Atlantic white cedar was established. Plants were grown in containers and in a replicated field plot. Height and width data were recorded from container- and field-grown plants and all taxa were evaluated for growth habit, growth rate, and summer and winter color. Color descriptions of foliage are provided based on the Royal Horticultural Society colour chart. Exceptional taxa were identified based on needle color, texture, growth habit, and growth rate. Superior green forms include Dirr Seedlings 1 and 2, `Emily', `Rachel', and `Okefenokee'. The superior variegated form is `Webb Gold'. Superior blue forms include `Blue Sport', `Glauca Pendula', and `Twombly Blue', and superior slow-growing forms include `Andelyensis', `Meth Dwarf', `Red Star', and `Heatherbun'. These taxa are recommended to growers, landscapers, and gardeners for production and use.
Five taxa of Atlantic white cedar [Chamaecyparis thyoides (L.) B.S.P.], `Blue Sport', `Okefenokee', Raulston Form, `Emily', and `Rachel', and one cultivar of Leyland cypress [×Cupressocyparis leylandii (Jacks. and Dallim.) Dallim.], `Haggerston Grey', were screened for resistance to Botryosphaeria and Seiridium cankers. Treatments consisted of Seiridium unicorne (Cke. And Ell.) Sutton, Botryodiplodia Sacc. sp., Fusicoccum Corda. sp. and the non-inoculated control. After 8 weeks, plants were measured for change in caliper at the wound site, change in plant height, and length and width of surface and interior cankers. Seiridium and Botryosphaeria canker development on Atlantic white cedar taxa was not significantly different than that on Leyland cypress. Seiridium unicorne was more pathogenic than Botryodiplodia sp. and Fusicoccum sp. on Atlantic white cedar and Leyland cypress with infection percentages of 100%, 84%, and 80%, respectively. Well-defined, sunken, resinous cankers developed on Leyland cypress plants infected with Seiridium unicorne, whereas Atlantic white cedar showed no visible surface canker.
Abstract
Depulped seeds of Liriope muscari (Decne.) L. H. Bailey pretreated with GA3 and/or kinetin and placed at 21°C for warm stratification, showed increased germination over unpulped seeds. Germination rates ranged from 87 to 100%. Identical growth regulator treatments resulted in no germination when the depulped seeds were cold stratified (5°C). Unpulped seed, pre-soaked in water for 24 hours or not soaked and given warm stratification germinated 38 and 25%, respectively. This suggested that the inhibition in unpulped seed is influenced by a water soluble inhibitor in the fruit wall.