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Kennett Square, PA, United States

Perera D.,Mississippi State University | Trader B.W.,Longwood Gardens Inc.
HortScience | Year: 2010

Slow growth rate of plantlets, few micro-shoots per explant, and slow root growth rate are restrictions of in vitro propagation of poinsettia (Euphorbia pulcherrima Willd. ex Koltz). The purpose of this research was to develop an efficient in vitro proliferation technique for poinsettia 'Prestige™ Red'.Explants (apical buds and axillary buds) placed on Murashige and Skoog (MS) basal medium containing only 6-benzylaminopurine (BA) and combinations of BA and indole-3-acetic acid (IAA) mostly produced red callus, which is productive and some white and gray-green calluses at the base of plantlets after 1 month, whereas explants in amedium without plant growth regulators (PGRs) produced no callus. Addition of IAA into the rooting medium increased rooting efficiency; plantlets grown in half-strengthMS salts and vitamins with 28.5 μMIAA initiated rooting 11 days earlier than the plantlets grown with no PGRs. Optimization of PGR concentrations during poinsettia micropropagation helped resolve previous restrictions of in vitro poinsettia proliferation. Chemical names used: 6-benzylaminopurine (BA); indole-3-acetic acid (IAA).

Evans M.R.,University of Arkansas | Taylor M.,Longwood Gardens Inc. | Kuehny J.,Louisiana State University
HortTechnology | Year: 2010

The vertical dry strength of rice hull containers was the highest of all containers tested. Plastic containers and paper containers had similar vertical dry strengths. Containers composed of 80% cedar fiber and 20% peat (Fertil), composted dairy manure (Cowpot), and peat had lower dry vertical dry strengths than the aforementioned containers but had higher vertical dry strengths than those composed of bioplastic (OP47), coconut fiber, and rice straw. Rice hull containers and paper containers had the highest lateral dry strengths. Rice straw, Cowpot, and plastic containers had similar dry lateral strengths, which were significantly higher than those of OP47, Fertil, coconut fiber, and peat containers. Highest dry punch strengths occurred with traditional plastic and Cowpot containers, while the lowest dry punch strengths occurred with OP47, Fertil, coconut fiber, peat, and rice straw containers. Plastic, rice hull, and paper containers had the highest wet vertical and lateral strengths. Plastic containers had the highest wet punch strength, while Fertil, Cowpot, and peat containers had the lowest wet punch strengths. When saturated substrate was placed into containers and the substrate surface and drainage holes were sealed with wax, plastic, OP47, and rice hull containers had the lowest rates of water loss per unit of container surface area, while peat, Fertil, and rice straw containers had the highest rates of water loss per unit of container surface area. The amounts of water required to produce a geranium (Pelargonium × hortorum) crop were significantly higher and the average irrigation intervals were shorter for peat, Fertil, coconut fiber, Cowpot, and rice straw containers than for traditional plastic containers. The amounts of water required to produce a geranium crop and the average irrigation intervals were similar among plastic, rice hull, and OP47 containers. Algal and fungal coverage on the outside container walls averaged 47% and 26% for peat and Fertil containers, respectively, and was higher than for all other containers tested, which had 4% or less algal and fungal coverage. After 8 weeks in the field, Cowpot containers had decomposed 62% and 48% in the Pennsylvania and Louisiana locations, respectively. Peat, rice straw, and Fertil containers decomposed 32%, 28%, and 24%, respectively, in Pennsylvania, and 10%, 9%, and 2%, respectively, in Louisiana. Coconut fiber containers had the lowest level of decomposition at 4% and 1.5% in Pennsylvania and Louisiana, respectively.

Zale P.J.,Longwood Gardens Inc. | Robarts D.W.H.,Ornamental Plant Germplasm Center | Robarts D.W.H.,Ohio State University | Jourdan P.,Ornamental Plant Germplasm Center | Jourdan P.,Ohio State University
Scientia Horticulturae | Year: 2016

The eastern North American creeping phlox (Phlox subulata L.) is a widely cultivated flowering groundcover with a history of breeding and selection. Little is known about genome size variation and ploidy of P. subulata and related taxa. Mean holoploid (2C) and monoploid (1Cx) genome sizes and ploidy were analyzed with flow cytometry for a germplasm collection (n = 53) of 11 morphologically similar creeping phlox taxa from natural plant populations, cultivars and hybrids obtained from nursery sources, and the related Microsteris gracilis. Holoploid genome sizes of accessions from natural populations were more variable than cultivated taxa and ranged from 7.47 to 22.86 pg and corresponded to diploid (2n = 2x = 14) tetraploid (2n = 4x = 28), and hexaploid (2n = 6x = 42) levels, but most accessions were diploid and genome size ranged from 7.60 to 8.47 pg. Two tetraploid accessions were discovered, but hexaploids were limited to one population of P. subulata. Most accessions consisted of a single cytotype, but intrapopulation differences in holoploid genome size were found among P. subulata and P. nivalis. The monoploid genome size of M. gracilis differed significantly from all Phlox, supporting separation of the genera. All cultivar accessions were diploid with genome sizes similar to wild diploid P. subulata, however Phlox × procumbens had a mean genome size (8.73 pg) intermediate to parental taxa, P. stolonifera × P. subulata, supporting hybrid origin. Knowledge of cytotype variation in Phlox germplasm will be useful for plant breeders, systematists, and conservationists. © 2016 Elsevier B.V.

At least three major gardens or arboreta in the USA have experienced periods of significant decline and death of mature Taxus (yews) in the landscape. The symptoms displayed on declining plants are described as chlorosis of the needles, partial defoliation, and death of some of the branches. Eventually, the entire plant may die, but they are typically removed before reaching this stage. Information on managing mature Taxus in the landscape is limited. The objective of this article is to review the literature on Taxus cultural practices and use the information to develop best management practices for Taxus in the landscape. Soil moisture is the most critical factor for health of plants in the landscape. Saturated soils create anaerobic conditions for roots and create an environment ideal for root infection by Phytophthora cinnamomi, the major root pathogen affecting Taxus. During planting, proper site selection and well-drained soil are crucial for the long-term survival of plants. After planting, irrigation should be managed to avoid saturated soil. Management from a nutritional standpoint is poorly understood. Maintaining an appropriate pH of 6.0 to 7.0 and fertilizing plants based on soil and tissue testing is recommended. More research needs to be done to determine optimal fertilization rates and appropriate nutrient concentration in tissue and in soil. When plants become symptomatic, soil should be tested for P. cinnamomi. If the fungus is present, appropriate chemical controls should be used. ©2014 International Society of Arboriculture

Panchen Z.A.,University of Delaware | Primack R.B.,Boston University | Anisko T.,Longwood Gardens Inc. | Lyons R.E.,University of Delaware
American Journal of Botany | Year: 2012

Premise of the study: The global climate is changing rapidly and is expected to continue changing in coming decades. Studying changes in plant flowering times during a historical period of warming temperatures gives us a way to examine the impacts of climate change and allows us to predict further changes in coming decades. The Greater Philadelphia region has a long and rich history of botanical study and documentation, with abundant herbarium specimens, field observations, and botanical photographs from the mid-1800s onward. These extensive records also provide an opportunity to validate methodologies employed by other climate change researchers at a different biogeographical area and with a different group of species. Methods: Data for 2539 flowering records from 1840 to 2010 were assessed to examine changes in flowering response over time and in relation to monthly minimum temperatures of 28 Piedmont species native to the Greater Philadelphia region. Key results: Regression analysis of the date of flowering with year or with temperature showed that, on average, the Greater Philadelphia species studied are flowering 16 d earlier over the 170-yr period and 2.7 d earlier per 1°C rise in monthly minimum temperature. Conclusions: Of the species studied, woody plants with short flowering duration are the best indicators of a warming climate. For monthly minimum temperatures, temperatures 1 or 2 mo prior to flowering are most significantly correlated with flowering time. Studies combining herbarium specimens, photographs, and field observations are an effective method for detecting the effects of climate change on flowering times. © 2012 Botanical Society of America.

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