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United States Department of Agriculture

Agricultural Research Service

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Location: Floral and Nursery Plants Research

2011 Annual Report

1a. Objectives (from AD-416)
Accelerate development of superior Hydrangea germplasm using wide hybridization, molecular markers, and ploidy manipulations. Develop, evaluate, and release improved germplasm of selected nursery crops species, including Hydrangea, Cornus, Clethra, and Styrax. Investigate physiological constraints with transplanting nursery crops and root system changes for better adaptation into production systems. Develop improved nursery production systems with an integrated approach of bio-plastic containers, plant water and nutrient use, and cultural management.

1b. Approach (from AD-416)
Use wide hybridization to improve H. macrophylla. Use molecular markers for studying genetic relationships and creating genetic linkage maps in Hydrangea. Develop a polyploid series in H. macrophylla. Develop, evaluate, and release improved germplasm of Hydrangea, Cornus, Clethra, and Styrax. Evaluate germplasm for nursery production and landscape potential. Determine root growth, root quality and plant performance in non-traditional nursery containers. Determine transplantability and survivability of bare root trees during nursery production and in post harvest landscape settings. Determine the relationship of cyclic irrigation and low nutrient inputs with container-grown ornamental trees. Determine the influence of irrigation and nutrient inputs on bio-based materials for container nursery production.

3. Progress Report
A seedling derived from hybridization of Dichroa febrifuga and Hydrangea macrophylla was selected for propagation and potential commercial evaluation. This seedling has mophead type flower heads, sepals that range in color from pink to purple to dark green, and inflorescences that stay attractive on greenhouse-grown plants for several months. A medium-sized oakleaf hydrangea seedling with large, upright inflorescences was sent to cooperators for evaluation. A Styrax japonicus cultivar was released under the name ‘Spring Showers’. This cultivar, which breaks bud 2 to 3 weeks later in the spring than most Japanese snowbell cultivars, is well-suited for use in areas of the country that frequently have late spring freezes. Six pellets (P 29, P 32, P 37, P 40, P 45, and PNaS) made of biobased plastic resin materials containing various amount of feather fibers, glycerol and other ingredients were evaluated. Roots of pepper failed to grow through a layer of P 29, P 32, P 37, and P 40 pellets; however, roots grew well through P45 pellets. Changes in the surface of pellets were observed using a low temperature scanning electron microscope (LT-SEM). Images indicated that growth of fungal hyphae is the most extensive in P 32, followed by P 29 and P 45 pots. A selection of cold hardy camellias and red-leaved crapemyrtles were planted in new field trials to evaluate for nursery production and landscape potential. A study of nutrient loss via substrate leaching in large nursery containers as influenced by time of daily irrigation and emitter selection was completed. Studies on the time of application of neonicotinoid insecticides for prevention of flatheaded borer attack on Acer rubrum were continued. Prototype bio-based nursery containers were evaluated for structural integrity and subsequent plant growth of selected herbaceous and woody perennials. An evaluation of nutrient input and irrigation management for container grown trees was continued.

4. Accomplishments
1. Release of a Japanese snowbell cultivar. Japanese snowbell (Styrax japonicus) is an attractive small tree that is well-suited for use in small residential landscapes or under utility lines; however, it is underutilized in the U.S., primarily because of its susceptibility to damage from late spring freezes. An ARS scientist in McMinnville, TN developed a Japanese snowbell selection that develops leaves 2 to 3 weeks later than most other cultivars, thereby allowing it to escape spring freeze damage. ‘Spring Showers’ grew 12 feet tall and 8 feet wide in 10 years and has dark green, lustrous foliage, upright growth habit and heavy flower production. ‘Spring Showers’ is well suited for use as a specimen plant or in a mixed border. Because of its delayed bud break, it is particularly useful in areas that are frequently subject to late spring freezes. This cultivar should result in increased sales for nurseries and garden centers and wider use of this small ornamental tree.

2. Colored shade cloth does not significantly alter growth of container-grown trees. ARS researchers in McMinnville, TN tested the influence of spectral light management on plant growth through the use of colored shade cloth. Measurements of plant height, number of internodes, dry weight, and trunk diameter were measured on container-grown willow oak, nuttall oak, and summer red maple. Results varied based on plant species; however, it was determined that tree morphology was not altered significantly to recommend the use of colored shade cloth during production. This information is useful to growers making decisions about container tree production practices.

3. A single application of soil-applied insecticides provides multi-year control of flatheaded appletree borer. ARS and Tennessee State University researchers at McMinnville, TN demonstrated that a single application of some neonicotinoid treatments can provide multi-year flatheaded appletree borer prevention, resulting in increased trunk growth in maple trees, and provide borer protection superior to trunk sprays. Soil-applied systemic insecticides (acephate, imidacloprid, clothianidin, dinotefuran, and thiamethoxam) and trunk-applied contact insecticides (chlorpyrifos and bifenthrin) were evaluated for flatheaded borer control and effect on red maple cultivar growth over a 4-year period. A one-time drench of Allectus (imidacloprid + bifenthrin) or Discus (imidacloprid + cyfluthrin) provided 2 to 4 years of protection from flatheaded appletree borers in maple trees. Soil-applied experimental imidacloprid tablets prevented borer damage in the third and fourth post-treatment years, but were not as effective as imidacloprid drenches in the first two years. Soil applied acephate tablets, chlorpyrifos (Dursban 4E) trunk sprays, or untreated control plants had borer damage each year, which totaled up to 41.7% damage by the fourth year. This information can be used by nursery growers to more effectively manage pesticide application in maple production.

Review Publications
Reed, S.M. 2010. ‘Ruby Slippers’ and ‘Munchkin’ Oakleaf Hydrangeas. HortScience. 45(12):1908-1909.

Last Modified: 06/28/2017
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