Little information is available on the reproductive behavior of Hydrangea macrophylla (Thunb. Ex J.A. Murr.) Ser. The objectives of this study were to investigate time of stigma receptivity, viability of pollen from sterile flowers, and self-incompatibility in this popular ornamental shrub. Pollen germination and pollen tube growth in styles were examined using fluorescence microscopy. Stigma receptivity was examined in cross-pollinations made from 1 day before anthesis to 8 days after anthesis. Maximum stigma receptivity for the two cultivars examined occurred from anthesis to 4 days after anthesis. Viability of pollen from sterile flowers was evaluated through pollen staining and observations of pollen tube growth. No significant difference in percent stainable pollen between fertile and sterile flowers was observed in any of the six taxa examined. Pollen germination and pollen tube growth were studied in cross-pollinations made using pollen from fertile and sterile flowers of two cultivars. For both cultivars, pollen tubes from fertile and sterile flowers grew to the same length and had entered ovules by 72 hours after pollination. Self-incompatibility was evaluated by comparing pollen germination and pollen tube growth in cross- and self-pollinations. In the five taxa examined, self pollen tubes were significantly shorter than cross pollen tubes in flowers that were examined 72 hours after pollination. This finding indicates the presence of a gametophytic self-incompatibility system in H. macrophylla.
Sandra M. Reed
Calvin Chong, R.A. Cline, and D.L. Rinker
Four deciduous ornamental shrubs [`Coral Beauty' cotoneaster (Cotoneaster dammeri C.K. Schneid); Tartarian dogwood (Cornus alba L.); `Lynwood' forsythia (Forsythia × intermedia Zab.); `Variegata' weigela (Weigela florida Bunge A.D.C.)] were grown in trickle-fertigated containers. There were eight media consisting of 25% or 50% sphagnum peat or composted pine bark, 25% sand, and the remainder one of two sources of spent mushroom compost; four media with 509″ peat or bark mixed with 50% spent mushroom compost; and a control medium of 10070 pine bark. Initially, higher than desirable salt levels in all compost-amended media were leached quickly (within 2 weeks of planting) and not detrimental to the species tested. Unlike cotoneaster, which showed no difference in growth (shoot dry weight) due to medium, dogwood, forsythia, and weigela grew significantly better in all compost-amended media than in the control. Growth of these three species was 20% greater in peat-based than in bark-based, compost-amended media. Dogwood and forsythia grew slightly more (+8%) with spent mushroom compost based primarily on straw-bedded horse manure than with one based on a blend of straw-bedded horse manure, wheat straw, and hay. The addition of sand (25%) to a mixture of 50% peat or bark and 25 % spent compost produced a medium with minimal compaction.
D.A. Raymond, C. Chong, and R.P. Voroney
Four containerized deciduous ornamental shrubs, [silverleaf dogwood (Cornus alba L. `Argenteo-marginata'), red-osier dogwood (Comus sericea L.), ninebark (Physocarpus opulifolius L.), and deutzia (Deutzia gracilis L.)] were grown in 12 composts containing (by volume) spent mushroom substrate (50%), waxed corrugated cardboard (WCC; 0%, 25%, or 50%), and/or pulverized wood wastes (PWW; 50%, 25%, and 0%). Supplemental N as poultry manure and/or soybean wastes was added to some composts. Growth (shoot dry weight, average of two seasons) of all species was better or similar in most composts compared with two controls (100% pine bark and 80% pine bark: 15% peat: 5% sand). Deutzia grew best in 50% WCC composts and other species in 25% WCC composts. Porosity characteristics of the composts were acceptable for container growing (50% to 60% total; 25% to 30% aeration). Total soluble salts were initially high and potentially phytotoxic, particularly in the 50% WCC composts but were quickly leached and resulted in no injury to plants. There were no symptoms of nutrient deficiencies or toxicities in any of the species tested. Foliar nutrient (N, I P, K, Ca, Mg, Mn, Zn, and Fe) concentrations in all species were within normal ranges, except for low Mn and Fe concentrations in red-osier dogwood during the second season.
Sandra M. Reed
Breeding efforts in Clethra alnifolia L., an ornamental shrub native to the Eastern U.S., are hindered by a lack of information on the reproductive behavior of this species. The objective of this study was to evaluate self-compatibility, time of stigma receptivity, and the relationship between time of pollen shed and stigma receptivity in C. alnifolia. Stigma receptivity and changes in floral morphology were monitored over a 7-day period beginning at flower opening. Pollen germination and pollen tube growth in styles were examined following self- and cross-pollinations using fluorescence microscopy. Seed set and germination were compared following self- and cross-pollinations. Anthers began to dehisce in `Hummingbird' and `Ruby Spice' the day after flowers opened, but stigmas did not become fully receptive to pollen until 2 days later. An increase in the length of pistils was observed following flower opening. Maximum elongation of pistils occurred at approximately the same time stigmas became receptive and could be utilized as an indicator of receptivity. While self-pollen tubes appeared to grow slightly slower than cross-pollen tubes, there was no indication of a self-incompatibility system acting at the stigmatic or stylar level in C. alnifolia. Self-pollinations of `Hummingbird' and `Ruby Spice' produced fewer seeds than did cross-pollinations of these cultivars. Germination of all seed obtained from this study was too poor to allow a comparison of germination rates of the self- and cross-pollinated seed. However, because a few self-progeny were obtained, emasculation is recommended when making controlled pollinations. The presence of a late acting self-incompatibility system or early-acting inbreeding depression was proposed as being responsible for the lower seed set following self-pollination.
William Klingeman, Charles Hall, and Beth Babbit
Though genetically modified (GM) ornamental cut flowers are already available commercially, U.S. academics and Green Industry growers have not assessed consumer perception about GM ornamental plants for landscape use. Because we must make inferences from studies of GM foods, we risk misunderstanding and alienating stakeholders and clients. If we misjudge the end-user, we jeopardize the market for future GM ornamental plant introductions. To address this gap, we surveyed Tennessee Master Gardener Volunteers in 2004. Respondents (n = 607) revealed that concern and belief about GM ornamental plants parallel U.S. expectation about GM foods. Average Master Gardener volunteer responses predict that GM ornamental plants would provide only slight benefits to both the environment and human health once used in the landscape. Compared with non-GM plants, GM ornamental plants are expected to be about the same or less invasive in the landscape. While all types of GM ornamental plants were expected to provide slight benefits, plant types were perceived differently with male respondents expecting perennials to yield the most environmental benefits and females indicating grasses and turf. Men and women also differed in their relative acceptance of GM ornamental plants, if genes were added from different types of organisms to achieve a genetic transformation of an ornamental shrub. Our results suggest that academic outreach and Green Industry marketing to promote new GM plant products should emphasize attributes of benefit, rather than GM transformation processes. Regardless, about 73% of TN Master Gardener respondents reported interest in buying GM ornamental plants if sold commercially, but the majority advocated a requirement for GM plant product labeling at point-of-sale.
G. Stephen Crnko, Edward W. Bush, and Allen D. Owings
A study was initiated to determine the effects of fall fertilization, specifically N application rate and additions of supplemental K on the production of woody ornamental shrub species. The influence of two slow-release sources of K (4- and 8-month) in the form of K2SO4, three K application rates (0, 1, 2 lb/yd3), and four incorporated application rates of N (0, 1, 2, and 3 lb/yd3) from Osmocote Plus+ 15-9-11 were evaluated on the growth of `Fisher Pink' Indian azalea, glossy abelia, and `Tuscarora' crape myrtle. Growth of `Fisher Pink' azalea, as determined by shoot height and shoot width, increased as N rate increased from 1 to 3 lb/yd3 when compared to the control. The resulting growth index improved at the 2 and 3 lb/yd3 N rate when compared to the 0 and 1 lb/yd3 N rates. Height and width of glossy abelia at the 1 lb N rate with or without supplemental K applications increased when compared to some glossy abelia at the 3 lb N rate (primarily those with supplemental K). Glossy abelia at the 2 lb/yd3 N rate with 2 lb/yd3 N from 4-month 0-0-46 had significantly greater shoot dry weight when compared to the 3 lb/yd3 N rate with 2 lb/yd3 N from 8-month 0-0-46. The 1 to 3 lb/yd3 N application rate had more of a response on growth index, visual quality, and visual color on `Tuscarora' crape myrtle as compared to the 0 lb/yd3 N rate. In this study, the potential influence of supplemental K applications on plant growth was mostly evident for glossy abelia at the 2 lb/yd3 N rate and was not evident on azalea or crape myrtle.
Christopher S. Cramer and Mark P. Bridgen
Mussaenda, a tropical ornamental shrub developed in the Philippines is being examined as a potential greenhouse potted crop in the United States. Showy sepals of white, picotee, pink or red and fragrant, yellow flowers make Mussaenda an attractive patted plans however, the profuse upright growth habit of some Mussaenda cultivars is undesirable for pot plant culture. With this in mind experiments were conducted to determine the effects of three growth regulators at two concentrations each, as well as the application method and the number of applications on Mussaenda plant height.
Three growth regulators, daminozide (B-Nine), ancymidol (A-Rest), and paclobutrazol (Bonzi) were applied at two commercially recommended rates and two application methods (spray or drench). The treatment were daminozide at 2500 ppm and 5000 ppm (spray), ancymidol at 33 and 66 ppm (spray) and at 0.25 and 0.50 mg/pot (drench), and paclobutrazol at 25 and 50 ppm (spray) and at 0.125 and 0.25 mg/pot (drench). In subsequent experiments, the same growth regulators were applied with an increase in concentration and either two or three applications. The treatments were daminozide at 5000 ppm (spray), ancymidol at 66 and 132 ppm (spray) and at 0.50 and 1.0 mg/pot (drench), and paclobutrazol at 50 and 100 ppm (spray) and at 0.25 and 0.50 mg/pot (drench).
The most attractive potted plants were produced with two applications of daminozide at 5000 ppm or two applications of ancymidol at 0.5 mg/pot (drench). Higher concentrations or additional applications excessively reduced plant height. Three spray applications of 132 ppm ancymidol also produced an attractive potted plant. Paclobutrazol sprays or drenches at any concentration or application number were ineffective for reducing Mussaenda `Queen Sirikit' plant height.
S.J. Stringer, J.M. Spiers, and A.D. Draper
Two new southern highbush blueberry cultivars, `Dixieblue' and `Gupton', will provide growers with new blueberry cultivars having excellent fruit quality that ripen relatively early in the season, during the profitable early fresh-market window. Berries of `Dixieblue' are light blue, medium in size, and their flat shape makes them most attractive. `Gupton' is very productive and berry quality is also excellent. The performance of these cultivars represent an improvement over most currently available southern highbush blueberry cultivars due to 1) their durability and performance on both upland and sandy soils endemic to the Gulf Coast and 2) consistent production of high quality fruit that will meet the demand for early ripening fresh-market blueberries. The new rabbiteye blueberry cultivar, `DeSoto', represents an improvement over currently available rabbiteye blueberry cultivars for late-season production. `DeSoto' produces medium-to-large fruit having excellent color, flavor, and firmness Plants of `DeSoto' are productive, vigorous but semi-dwarf, upright and spreading. It's semi-dwarf growth habit, which is unique among currently grown rabbiteye blueberries, results in bushes that attain a maximum height of about 2 meters upon maturity, reducing the necessity of top-pruning that is required for all other cultivars. `DeSoto' blooms two to three weeks later than early-to-mid season cultivars such as `Climax' and `Tifblue', providing insurance against late-spring freezes. Similarly, its fruit mature 21 to 14 days or more, respectively after these same cultivars. `DeSoto' will provide niche market blueberry growers with a new cultivar having productivity, plant vigor, fruit quality, and very late ripening period that will extend their marketing season. The new evergreen ornamental blueberry, `Native Blue', is low growing, compact and finely branched with small glaucous leaves, traits that are quite typical of V. darowii. `Native Blue' has beautiful foliage that changes color in different seasons. Mature leaves are darker green while newer growth exhibits a light pinkish hue that changes to a bluish green. Other desirable characteristics of `Native Blue' are its dwarf growth habit, hardy and vigorous growth, and its capacity for a high level of fruit production that serves as an attractant to birds and other wildlife. `Native Blue' will provide southeastern U.S. nurserymen, landscapers, and homeowners with a novel and beautiful new ornamental shrub that will complement plantings of azaleas, camellias, crepe myrtles, etc.
Sandra M. Reed and Margaret R. Pooler
Clethra alnifolia L. (family Clethraceae Klotzsch.) is an ornamental shrub that is native to the eastern United States ( Wilbur and Hespenheide, 1967 ). While sometimes called summersweet or sweet pepperbush, it is more commonly known as clethra
Mark H. Brand, Jessica D. Lubell, and Jonathan M. Lehrer
corky ridged stems, orange aril fruits, and exceptionally brilliant and dependable red fall foliage color ( Dirr, 2001 ). Historically, E. alatus has been popular as an ornamental shrub for challenging landscape situations because of its tolerance to