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Grants are awarded to research projects that yield practical benefits for growing or enjoying rhododendrons or yield new insights into the biology, geographical distribution or history of species or hybrid rhododendrons.

2014 Awards

Assessing and Increasing the Genetic Diversity in Cultivation of Three Red-Listed North American Rhododendrons: R. eastmanii, flammeum & vaseyi.
Thomas E. Clark
Polly Hill Arboretum, West Tisbury, MA

The Red List of Rhododendrons (2011) published by Botanic Gardens Conservation International (BGCI) indicates that approximately 25% of all Rhododendron taxa in the world are under threat of extinction in the wild. The objectives of this two-year project is assess these three species under cultivation in botanical gardens, organize two collaborative collecting trips to various parts of the species ranges to collect broad genetic variation and to establish ex-situ conservation collections. An additional goal is to make seed available to a wider audience through the ARS seed exchange and prepare distributions for cooperating botanical gardens and arboreta.

Counting Chromosomes of Species of Rhododendron Subgenus Rhododendron Section Schistanthe (Vireya) Having Flow Cytometry Scores
Well Above the Range Normally Expected for Diploid Species in Rhododendron Subgenus Rhododendron.

Dr. Ryan Contreras
Ornamental Plant Breeding
Department of Horticulture
Oregon State University, Corvallis, OR

Sally and John Perkins
Salem, NH

Dr. Joao Loureiro
Plant Ecology and Evolution Group
Center for Functional Biology
Department of Life Sciences, University of Coimbra, Coimbra, Portugal

This research is a further continuation of a previously funded project by the Research Foundation of the ARS. In the past decade, much has been learned about the ploidy (chromosome number) of species in the genus Rhododendron by combing flow cytometry (estimating genome size by measuring relative DNA amounts in individual cells) and chromosome counting. Tetraploids or double the normal chromosome number was observed several native azalea species. Previous studies of Schistanthe (Vireya) species showed they had high flow cytometry scores suggesting polyploidy. The goal of this research is to determine if the increase in cytometry scores is due to an increase in number of chromosomes and/or the size of chromosomes. The significance would be valuable to hybridizers in production of Vireya hybrids and to the understanding of relationships between related species.

Identification of Reference Genes for Expression Analysis of Cold Acclimation Genes in Rhododendrons Using Real-Time PCR.
Dr. Malgorzata Czernicka
Unit of Genetics, Plant Breeding and Seed Science
Institute of Plant Biology and Biotechnology, University of Agriculture in Krakow, Krakow, Poland

Freezing temperature is one of the main and deciding environmental factors limiting growth and development of rhododendrons. For extremely low temperature acclimation ability in rhododendrons, dehydrins and the early light-induced proteins are responsible and these proteins are known genetic markers for cold hardiness. This study will analyze the expression of cold-related genes using real-time PCR. PCR stands for polymerase chain reaction which is a technique for rapidly replicating small amounts of DNA for further analysis. The main objective of this study is to select the most reliable reference genes for PCR analysis under cold stress conditions. The expected results may help in the selection of the most cold hardy individuals for breeding strategies in order to produce decorative and frost resistant rhododendrons.

Linking plants to soils: Are novel soils contributing to native Rhododendron persistence and spread under environmental change?
Alix Pfennigwerth & Jennifer Schweitzer
University of Tennessee, Knoxville, TN

This research proposes to study how genetic variation in Rhododendron species influences physiological performance under a changing climate, including increasingly fluctuating temperatures, moisture regimes, soil nutrient cycling, and interactions with pathogens, herbivores, and beneficial microbes. Results of this study would directly benefit horticulturists by providing information on selecting Rhododendron varieties best adapted to particular environmental conditions, as well as potential areas of natural hybridization under range specific scenarios. Rhododendron maximum (Rosebay Rhododendron) is an important ecological component of southern Appalachian forests and will be the focus of this study. The objective is to see if different populations in Virginia, Tennessee and North Carolina vary phenotypically and/or genetically across environmental gradients. One goal would be to inform and improve rhododendron cultivation practices by examining genetic variation and plant-soil linkages across these gradients.

Developing an in-vitro selection method for Rhododendron alkalinity tolerance using the cultivars 'Inkarho' and 'Haaga'.
Dr. Stan Hokanson
University of Minnesota, St. Paul, MN

Soil pH has a large effect on the types of plants that can be grown in a given soil. The alkalinity (pH >7) or acidity (pH <7) of a soil is a major factor in the solubility for vital nutrients that plants use to maintain functions essential to proper growth and development. Through plant breeding, 'Inkarho' rhododendrons have been found to exhibit a tolerance to alkaline conditions. This cultivar provides a unique opportunity to gain an understanding of the physiological mechanisms supporting elevated pH tolerance. In using a rhododendron cultivar that is known to be more tolerant of alkalinity and comparing it with a known intolerant variety, mechanisms for intrageneric (within the genus Rhododendron) variation can hopefully be documented and a precedent established for the future selection of tolerant cultivars. This in-vitro (in a laboratory vessel or other controlled environment) research model will test plants in tissue culture using pH micro-electrodes with subsequent mass spectrometer analysis of media and root tissues. Existence of similar intrageneric variation can then be sought out in other landscape plants and horticultural crops to expand growing ranges and improve plant performance across a large geographic area.

2013 Awards

Developing an in-vitro selection method for Rhododendron alkalinity tolerance using the cultivars 'Inkarho' and 'Haaga'.
Dr. Stan Hokanson
University of Minnesota, St. Paul, MN

Soil pH has a large effect on the types of plants that can be grown in a given soil. The alkalinity (pH >7) or acidity (pH <7) of a soil is a major factor in the solubility for vital nutrients that plants use to maintain functions essential to proper growth and development. Through plant breeding, 'Inkarho' rhododendrons have been found to exhibit a tolerance to alkaline conditions. This cultivar provides a unique opportunity to gain an understanding of the physiological mechanisms supporting elevated pH tolerance. In using a rhododendron cultivar that is known to be more tolerant of alkalinity and comparing it with a known intolerant variety, mechanisms for intrageneric (within the genus Rhododendron) variation can hopefully be documented and a precedent established for the future selection of tolerant cultivars. This in-vitro (in a laboratory vessel or other controlled environment) research model will test plants in tissue culture using pH micro-electrodes with subsequent mass spectrometer analysis of media and root tissues. Existence of similar intrageneric variation can then be sought out in other landscape plants and horticultural crops to expand growing ranges and improve plant performance across a large geographic area.

Plant functional traits associated with diversification of Rhododendron section Schistanthe into the tropics.
Dr. Erik T. Nilsen
Department of Biological Sciences
Virginia Tech University, Blacksburg, VA

The main goal of this study is to evaluate what structural and physiological traits changes in accordance with the diversification of Schistanthe (Vireyas). Many different leaf anatomical traits (thickness, mesophyll area and thickness, idioblast expression, stomatal density and pore length) and wood anatomical traits such as different vessel morphologies will be studied. The resulting anatomical and physiological spreadsheets will then be mapped onto the phylogenic tree for Shistanthe. A proposed outcome is that this analysis will verify how functional traits have changed during diversification. Greater knowledge of plant ecology and the importance of functional traits can shape the maintenance program for plants in the horticultural trade. There is a strong need for conservation of Rhododendron species particularly in Southeast Asia due mostly to habitat damage. The more information that is known about ecology and physiology of these species, the easier it will be to improve conservation strategies and understand plant response to climate change.

Rhododendron diversity and leaf functional traits across elevation gradients in tropical, subtropical, and temperate regions of SE Asia.
Melissa Whitman
University of Nebraska-Lincoln
School of Biological Sciences, Lincoln, NB

This multi-year project addresses Rhododendrons diversity, and leaf functional traits, across elevation gradients for tropical, subtropical, and temperate regions of SE Asia. Rhododendron with epidermal scales, from Schistanthe (Vireya), Rhododendron, and Pogonathum, will be the focus of this study. Distribution range per species will be estimated using georeferenced herbarium records and information from botanical collections. Functional traits (specific leaf area, % nitrogen, % lignin, scale density) for 150 rhododendron species will be quantified using leaf samples collected from botanical gardens. Preference will be made towards plants grown from wild collected cuttings, and species from resolved polygenetic trees to account for evolutionary history. Data on geographical range, and functional traits, will then be integrated to test whether or not species at lower elevations, or within tropical regions, have more defenses against herbivory than species at higher elevations, or within temperate regions. Practical application of this project includes mapping of Rhododendron diversity for international conservation efforts, as well as estimates of climatic range size, and possible resistance herbivory. Results can then be used to inform selection of species for horticultural use.

2012 Awards

Determining the Ploidy of Rhododendron Hybrids and Species Using Flow Cytometry
Sally and John Perkins
Salem, NH

Joćo Loureiro
Department of Life Sciences
University of Coimbra, Coimbra, Portugal

Project objective is to use flow cytometry to identify the ploidy of: 1)  named ploidy elepidote hybrids suspected of being polyploids, 2)  lepidote species concentrating on subsections Cinnabarinum, Heliolepida, Ledum, Lapponica, Maddenia, Tephropepla, and Triflora, 3)  Vireya species concentrating on alpine species and species closely related to laetum and macgregoriae, and 4)  wild populations of subsection Ledum concentrating on mixed populations including x columbianum, glandulosum and groenlandicum.

2011 Awards

Microsporogenisis in Rhododendrons: The development of pollen and tapetal cells in relation to periods of low temperature.
Miroslavov Evgeny Komarov
Botanical Institute of Russian Academy of Sciences, Petersburg, Russia

Evaluation of southern-adapted R. hyperythrum hybrids for resistance to Phytophthora cinnamomi
based on roots and shoot symptoms in the field.

Stephen Krebs
David Leach Research Station of Holden Arboretum, Kirtland, OH

Developing rhododendron hybrids that are heat tolerant as well as disease and insect resistant
primarily using R. hyperythrum as a parent.

Stan Southland
Chapel Hill, NC

2010 Awards

Cellular Mechanism of Thermonasty in Rhododendron: Are Membrane Water Channel Proteins (aquaporins) Involved?
Dr. Rajeev Arora
Department of Horticulture, Iowa State University, Ames, IA

One of the goals of this investigation is to gain fundamental insight into the mechanism of cold tolerance in rhododendrons. Thermonasty is the term applied to the leaf drooping and curling phenomenon observed in many, but not all, evergreen rhododendrons. This research will study the cellular mechanisms of thermonasty as water moves across leaf cell membranes which then control leaf movement. It has been proposed that water movement across membranes is likely regulated by water channel proteins called aquaporins. This study will attempt to isolate the genes associated with seasonal cold hardening. A specific objective will be to investigate whether there are changes in gene expression, in a predicted pattern, with temperature- induced leaf curling and uncurling. The two species to be studied, R. catawbiense and R. ponticum, have different behavior with regard to leaf curling in winter.

Nonanoic Acid and Trichoderma Isolates for Management of Botrytis and Ovulinia Petal Blight in Azalea
Dr. Thomas Gianfagna
Plant Biology and Pathology Department, Rutgers University,New Brunswick, NJ

This research project investigates the use of isolated compounds from specific bacteria (Trichoderma species) that may have antifungal properties against Botrytis and Ovulinia petal blight in azaleas. Biocontrol would be an alternative to synthetic pesticides. Evergreen azalea cultivars of 'Hino crimson' and 'Gumpo Pink' will be used in the experimental model under controlled greenhouse conditions. If research proves a beneficial effect, the anticipated benefits of a biofungicide, which is more environmentally friendly than conventional fungicides, would be welcomed by azalea growers where petal blight is a major problem.

Functional Significance of Leaf Idioblasts in Vireya Leaves to Water Relations and Photosynthesis.
Dr. Erik Nilsen
Biology Department, Virginia Tech, Blacksburg, VA

The overall goal of this research in Vireya rhododendrons is to learn the functional significance of leaf attributes to improve understanding of Vireya ecology and thereby promote the conservation of Vireya diversity. Specifically, the research will focus on the functional significance of idioblasts to leaf water relations and photosynthesis. Idioblasts are very large cells found to be present in the leaves of all Vireya species but not other rhododendrons. Research with other plant groups suggests that idioblasts may be important for water balance, photosynthesis, temperature balance, chemical storage, oxalate crystal synthesis, and defense against herbivores. This research will focus on water balance and photosynthesis.

2009 Awards

Molecular Studies of Rhododendron subgenus Vireya: Implications for International Programs
in Conservation Collection Management and Plant Development.
Dr. Susan E. Gardiner/Davis
The New Zealand Institute for Plant and Food Research
Palmerston North, New Zealand

The researchers will use both molecular and conventional taxonomic methods to investigate the diversity of Rhododendron subgenus Vireya (vireyas) in New Zealand and the USA then examine the diversity in relation to conservation, cultivation and plant development. This project will take two years to complete. The first phase is a survey to build a database and literature review to support taxonomic and molecular research. The second phase will be to use molecular markers, specifically DNA, to examine the broader range of vireyas in the Rhododendron Species Botanical Garden as well as in New Zealand with the goal of determining the value of conserving vireyas that may be endangered of being lost in the wild.

Conservation and Reintroduction of Rare, Endemic and Endangered
Rhododendron Species in the Indian Eastern Himalayas.

Dr. Shaily Menon
Biology Department, Grand Valley State University, Allendale, MI

Summary of Proposal The proposed work will focus on the Eastern Himalayan Region of Arunachal Pradesh state of India. Rhododendrons are the most dominant of the high-altitude flowering plants ranging in elevations from 1500 m to 4500 m. Approximately 72 Rhododendron species and 19 varieties are known to India. The study involves extensive field surveys of temperate and alpine forests. The goal is to prepare distribution maps of selected endemic and rare or threatened rhododendron species and identify limiting ecological factors limiting their distributions. This is a two year study with the second year to involve predictive models of species distributions and probable sites will be surveyed in the field to validate the accuracy of the models. The research hopes to make significant contributions to building conservation action plans for the management of habitat and biodiversity conservation.

Creating New Hybrid Rhododendrons for Improved Fragrance in
Yellows, Oranges and Purples, Handsome Foliage and Heat Tolerance.

Kristi O'Donnell
Director Meerkerk Rhododendron Gardens Greenbank, WA

Meerkerk Rhododendron Gardens, founded in 1961, has been involved with hybridizing rhododendrons since the 1970's. The projects objective is to create fragrant hybrid rhododendrons with uniquely pigmented flowers and handsome foliage with a tolerance of drier summer soils. On Whidbey Island, because it is in a rain-shadow, summers are drier than surrounding regions. Some crosses will use R. macrophyllum in the hopes that hybrids will be more tolerant of drier conditions. The public is also often unaware that many rhododendrons are fragrant. If the goal is obtained of developing hybrids with fragrance in colors such as yellow, orange or deep purple, good looking form and foliage as well as tolerance of drier soils, then this would help the broader promotion of rhododendrons.

2008 Awards

Nonanoic Acid and Trichoderma Isolates for Management
of Botrytus Petal Blight and Phytophthora Dieback
Thomas J. Gianfagna
Department of Plant Biology and Pathology, Rutgers University, New Brunswick, NJ

It has been discovered that some microorganisms have antibiotic control of fungal pathogens. The research involves isolation of specific compounds from specific kinds of bacteria and testing their effect on two kinds of fungal disease under controlled greenhouse conditions. The anticipated benefits to rhododendron growers are a potential biofungicide that will be cheaper than currently registered conventional fungicides and which is environmentally friendly.

Identification and Classification of Rhododendron Powdery Mildew in the Pacific Northwest
Dean A. Glawe
College of Forest Resources, University of Washington, Seattle, WA

Powdery mildew is a serious disease of susceptible rhododendron cultivars and species causing leaf spotting, defoliation, and reduced growth. This is more of a problem in different regions of the country, but particularly in the Pacific Northwest. The taxonomy of powdery mildew is very complex involving many different species. This project will characterize the morphology of powdery mildew fungi on Rhododendron species using light and scanning electron microscopy and will assess relationships among these fungi using nucleic acid sequences. The objective is to use this classification information to determine the correct names of the North American powdery mildews on Rhododendron species. This research will enable plant pathologists and rhododendron breeders to target more effectively their efforts in controlling powdery mildew.

Genome Sizes in Rhododendron ssp.
Leen Leus
Institute of Agricultural and Fisheries Research, Melle, Belgium

The numbers of chromosomes, also known as ploidy levels, are of interest for plant breeders as polyploidy (extra sets of chromosomes) can influence characteristics of growth vigor or in the case of ornamentals, the ornamental value. The analysis of the DNA content can give more information than just the ploidy level. Although a lot of information is available about the number of chromosomes among certain genotypes of rhododendrons, little information is available about the genome size. Genome size is important from a phylogenetic point of view and also important for plant breeding.

Are There Toxins in Rhododendron Nectar?
Geraldine A. Wright
Newcastle University, Newcastle upon Tyre, United Kingdom

The plant tissues of rhododendrons are know to contain toxins that affect nerve and muscle cells when ingested by animals. There are also accounts of "mad honey" consumed by humans reported back to ancient history. The question arises as to why rhododendrons have toxin in the nectar they offer to pollinators. The research will try to determine how widespread toxins are throughout a large number of different Rhododendron species. This proposal describes nectar as the "currency" between pollinators and plants and it is the nectar that attracts many insects. The objective of this research is to determine whether the presence of rhododendron-specific toxins (grayanotoxins) in nectar correlates with pollinator type predicted on the basis of rhododendron floral traits.

2007 Awards

Improving Fertilizer and Water Use Efficiency of Container-Grown Rhododendron
Carolyn F. Scagel
USDA-ARS-Horticulture Crops Laboratory, Corvallis, OR

The objective of this multi-year study is to characterize the seasonal dynamics of nitrogen uptake and internal cycling in evergreen and deciduous rhododendron cultivars. The effects of liquid and controlled release fertilizer on plant growth and nitrogen uptake will be compared and the influence of nitrogen on water use and photosynthetic performance will be assessed.

It is hypothesized that excess nitrogen during nursery production decreases the efficiency of water use and the quality of container grown rhododendrons. This has important environmental as well as economic implications. Avoiding excess fertilizer run-off and increasing fertilizer efficiency is a hopeful expected outcome this research.

Rhododendron Decline of the Southern Appalachian Mountains: Holistic Study of Biotic and Abiotic Factors Compared Between Healthy and Declining Stands
William D. Starrett
Mississippi State University, Mississippi State, MS

Dieback or decline of Rhododendron maximum has been reported in an increasing number of areas in the southern Appalachians and the Great Smokey Mountains National Park. Because of the uncertainty of causal factors, a holistic approach will be taken in an effort to identify abiotic or biotic factors that might cause wild Rhododendron maximums to decline at more than 10 sites. Specifically, the holistic approach proposed will compare site factors responsible for increased plant stress, occurrence and importance of fungal pathogens, and changes or loss of mycorrhizal associates compared between healthy and declining stands of rhododendrons. In addition to helping manage rhododendron decline, the data collected may also help aid in the increased understanding of forest decline and the factors involved.

Breeding Polyploid Rhododendrons and Azaleas
Thomas Ranney
Department of Horticultural Science, North Carolina State University, Fletcher, NC

Polyploids are organisms that have more than two complete sets of chromosomes. Polyploidy will be induced chemically in rhododendrons resulting in triploid and tetraploid sets of chromosomes. The objective is to determine ploidy level and genome size of a diverse range of species, hybrids and cultivars of rhododendrons using a combination of flow cytometry and light microscopy.

2006 Awards

Mechanisms for Winter Photoprotection in Rhododendron subsection pontica: a physio-genetic analysis
Dr. Stephen Krebs
The Holden Arboretum, Kirtland, OH

Temperature-leaf leaf movement, termed thermonasty, possibly functions in evergreen Rhododendron species by reducing oxidative stress in leaves caused by winter sunlight.  Thermonasty varies among Rhododendron species and appears to be positively correlated with cold hardiness.  This proposal explores that relationship and asks whether thermonasty is a necessary condition for winter hardiness.

The hybridization of R. catawbiense (exhibits thermonasty) and R. ponticum (does not exhibit thermonsaty but has phototolerance to winter sun) in the Waterer hybrids created the "ironclad rhododendrons" resulting in greatsuccess in growing under a wide range of conditions.  This research proposes to test the hypothesis that more than just thermonasty, possibly a biochemical response, is responsible for cold hardiness and that there may be an additive effect by relying on different mechanisms for photoprotection from winter sun.

Understanding the Mechanism of Cold Hardening in Rhododendrons:
Functional Analysis of a Cold Acclimation-Responsive Dehydrin Gene/Protein

Rajeev Arora
Iowa State University, Ames, IA

The overall objective of this project is to study the roll of a specific Rhododendron catawbiense gene, RcDhn5, in protecting plants from freeze injury.  This gene encodes a "cold stress-responsive" protein called dehydrin.  The goal is to obtain enough purified 25 kDa dehydrin protein, the product of the RcDhn5 gene, to conduct biochemical assays for its stress-protective properties.  Bioassay tests will be performed by adding the protein to a known cold sensitive enzyme, such as LDH and/or MDH, to see if this protein has a freeze-protection and/or dehydration-stress protection properties.

The significance of the research would be in the identification of genes responsible for conferring freezing tolerance and possibly in the future use genetic engineering to develop new selections of plants with ornamentally superior traits.

Mapping the Dstribution of Rhododendron arboreum ssp. nilagiricum (Zenker) Taag,
Using Ecological Niche Modeling and Develop Conservation Plan

Amarnath Giriraj
Department of Ecology
French Institute of Pondicherry, Pondicherry, India

Rhododendron is an important genus occurring in the high altitudes of the Himalayan region, having ecological significance and economic importance in addition to its graceful flowers.  India records 72 Rhododendron species, 20 subspecies and 19 varieties.

Precise information on a species including distribution and ecology is important in developing management and conservation strategies.  The project objectives are to prepare distribution maps of the Western Ghats region for Rhododendron arboreum ssp. nilagiricum, identify ecological limiting factors for distribution, analyze management practices in locations not under conservation, assess the threat status for this species, and identify possible areas for reintroduction or range extension.

The significance of the research will be to prepare a conservation action plan for the management of the habitat and Rhododendron arboreum ssp. nilagiricum species for sustainable biodiversity conservation.

2005 Awards

Rhododendron Database Project – Hybrid Phase
Dr. Forrest E. Bump, Jeffery M. Chase and Carol A. McCarthy
Forest Grove, OR

The goal of this project is to develop a not-for-profit electronic Internet and computer-searchable Rhododendron Database containing multiple characteristics of rhododendron species and hybrids.  The database resource will be accessible to rhododendron experts, hybridizers, nursery professionals, American Rhododendron Society members and the general public.  The database will be utilized to identify, contrast, and compare the characteristics of various rhododendrons.  Each plant record will have 40-50 different identification features and plant characteristics.  The database will provide a comprehensive analytical tool for those studying and developing rhododendrons.

Ploidy Manipulation and DNA Quantification for the Genetic Improvement of Rhododendron
Eric Zeldin
Principal Investigator
University of Wisconsin-Madison
Department of Horticulture, Madison, WI

Significant past improvements have been made to the cultural and ornamental characteristics of rhododendrons, however, continuing technological advancements provide researchers with an increasing ability to utilize the incredible diversity within the genus to achieve further progress.  This research project will utilize flow cytometry (a method for quantifying DNA content in individual cells), ploidy manipulation (changing chromosome number from diploid to tetraploid and even to triploid and interspecific hybrids (hybridizing between different rhododendron species).  The overall strategy is to develop Rhododendron varieties that are improved in bloom quality, fragrance and climatic adaptability.  A rare Japanese native, R. uwaense, will be used as a breeding parent because it possess highly fragrant flowers and substantial heat tolerance.  Flow cytometry will also help identify the phylogenetic relationship of R. uwaense with other subgenera.  Hybrid seedlings from R. uwaense and crosses of tetrapoid R. catawbiense with diploid ponticum spp. will hopefully result in triploid progeny.  Triploid plants in previously studied genera including Vaccinum, Betula and Viburnum have resulted in new desirable traits.  Hybrid seedlings from this research project will also be tested for zone 3 winter hardiness.

2004 Awards

Identifying Taliense Rhododendrons Using Leaf Waxes
Professor David W. H. Rankin
University of Edinburgh
Edinburgh, UK

The subsection Taliensia includes several species such as R. aganniphum, R. alutaceum, R. phaeochrysum and R. roxieanum, which are highly prized for their flowers and foliage.  Taxonomy is difficult due to natural hybrid swarms and one of the primary goals of this research is to use the chemistry of leaf waxes as markers for species characterization and identification.  A study of leaf waxes is much less expensive than DNA analysis.  The significance of the work will be to see if species in the Taliensia subsection can be characterized and then confirm if species can be differentiated from hybrids.  This will help growers and botanists with implications for both conservation and horticulture.

Utilizing Allopolyploid Azaleodendrons for Breeding Superior
Cold Hardy, Fragrant, Evergreen Rhododendrons

Dr. Thomas G. Ranney
North Carolina State University
Fletcher, North Carolina

Hybrid sterility is often a problem encountered when chromosomes do not match up between two parents during plant hybridizing.  Induction of polyploidy (syn. allepolyploidy), which is artificially increasing the number of chromosomes, can often restore fertility.  The putative azaleadendron called 'Fragrant Affinity' will be the cultivar analyzed in this study.  Effort will be made to identify the parentage, possibly R. catawbiense x R. viscosum or R. ponticum x R. viscosum, of 'Fragrant Affinity'.  One goal of the research is to develop documented fertile allepolypoids of 'Fragrant Affinity' with implications for further successful hybridizing.

2003 Awards

Development of a USDA Zone 4A Rhododendron Cold Hardiness Trial/Display Garden
Dr. Stan Hokanson
Department of Horticultural Science
University of Minnesota, St. Paul, MN

The primary goals will be to develop a wider range of flower colors and more reliably bud-hardy rhododendrons for Zone 3/4 landscapes.  The proposed trial/display garden will be on the grounds of the Minnesota Landscape Arboretum in Chanhassen, Minnesota and will be open to the public.  For many visitors, viewing the proposed display garden would be a rare encounter with evergreen rhododendrons.  A local architect has donated the landscape design and funds will be used to properly prepare planting areas.

The Effect of Phosphorus in Different Formulations on the Flower Bud Formation of Rhododendrons
 Frank Brouse
Brouse Nursery, Norristowm, PA

The purpose of the research is to show the effect of phosphorus, in different formulations, on the flower and vegetative bud set of elepidote rhododendrons ('Roseum Pink', 'Catawbiense Alba', and 'Wyandanch Pink').  Plant age and light conditions have an effect on flower bud set, but there has long been a debate about the importance of adding phosphorus as well as other nutrients to stimulate more flowering.  Controlled nursery conditions over a three-year period will test the effects of di-ammonium phosphate, super-phosphate and starter fertilizer (9:46:15) on the ratio of flower buds and vegetative buds.  If positive results are found, then a recommendation on how to increase flowering will significantly benefit all growers of rhododendrons.

Collection of Winter Hardy Rhododendrons at the Central Siberian Botanical Garden in Novosibirsk, Russia
Elena Chernykh and Dr. Tatyana Novikova
Central Siberian Botanical Garden, Novosibirsk, Russia

The goal is to find winter hardy genotypes of rhododendron species that will grow well under the conditions of Novosibirsk.  Russian botanists recognize 12-15 species native to Western and Eastern Siberia and the Russian Far East Region.  Species of greatest interest are R. ledebourii, R. dahuricum, R. mucronulatum and R. sichotense.  These species exhibit tremendous variations in size and flower color.  Micropropagation techniques will be applied to selected clones and seed will be sent to the ARS.

2002 Awards

Ecology of Vireya Species in their Natural Habitat
Dr. Erik T. Nilsen
Biology Department, Virginia Tech

A new giant cell type with unusual cellular morphology has been identified as being unique to vireya rhododendrons.  The goal of this study was to validate this observation in natural populations of vireyas in New Guinea, take tissue samples for later DNA and microscopic laboratory analysis, and do field experimentation measuring photosynthesis in response to various light and carbon dioxide conditions.  Outcomes will provide a greater understanding of the ecology of vireyas and the function of the newly discovered cell type.

Physiological Study of Deacclimation in Rhododendron
Dr. Rajeev Arora and Dr. Stephen L. Krebs
Department of Horticulture, Iowa State University

The specific objectives of the study are to characterize the timing and speed of deacclimation, which is the opposite of fall acclimation for winter, through a time-course study of five Rhododendron species that vary in their freezing tolerance (R. maximum, R. ponticum, R. carolinianum, R. dichroanthum and R. arboretum).  The study will also identify and quantify proteins (dehydrins) whose relative abundance appears to be affected by a winter thaw treatment.  Possible results include an understanding of how plants acclimate to winter temperature and maintain deacclimation.  This will be useful for evaluation of plants in the landscape and breeding programs.

An Evaluation of Powdery Mildew Disease on Deciduous Azaleas Cultivars
Dr. Stan Hokanson and Dr. Stephen L. Krebs
Department of Horticultural Science, University of Minnesota

The researchers will evaluate over a two-year period, 50 deciduous azalea cultivars and species in two separate locations (Minnesota and Ohio) for resistance to powdery mildew.  A second phase includes a survey of additional numbers of cultivars and species in eastern North American public gardens, significantly broadening the study.  While plant pathology is not the primary focus, attention will be given to identifying the fungal species involved.  An expected outcome is not only a "good doer list" of species and cultivars, but ratings will assist breeders for further plant introductions.

2001 Awards

Cold Acclimation and Freezing Tolerance in Rhododendron maximum
Dr. Gary C. Harris
 Biology Dept., Wellesley College

Techniques of protein extraction and analysis by two-dimensional gel electrophoresis will be refined and key leaf and thylakoid membrane proteins will be identified during a yearly developmental cycle.  A through understanding of the molecular aspects of cold acclimation and freeze tolerance could be of great significance in efforts to improve varieties and extend the growth range of rhododendron species into colder climatic zones.

Nursery Production and Landscape Performance of Azaleas
Dr. Gary J. Keever
Dept. of Horticulture, Auburn University

The overall objective of this project is to identify and promote superior azalea selections.  A wide range of cultivars will be evaluated during nursery production (propagation and container production through flowering) for two years and for at least five years in the landscape.

Collection of Rhododendron sect. Vireya in Sulawesi, Indonesia for Studies
Into Their Evolutionary Relationships and Biogeography
Dr. Lyndley A. Craven
Principal Research Scientist
Australian National Herbarium, CSIRO Plant Industry

The objective of the project is to obtain herbarium and live material, for both DNA and morphological studies, of a group of species that is not well known.  Material for propagation will be collected when possible.  Cutting material will be sent to the Rhododendron Species Foundation after establishment in Australia.  Wild-collected seed will be sent to the Vireya seed exchange.

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