Professor of Environmental Horticulture and Nursery Crops Extension Specialist
During his 38-year career, Dr. Knox conducted applied research and extension programming that focused on plant evaluation and plant health (plant-pest-disease-environment interactions). Goals of his plant evaluation program are to:
- identify, evaluate and distribute landscape plants to benefit the Green Industry and Florida gardeners
- minimize impacts from pests and diseases
- promote pollinator health
- reduce invasiveness by non-native plants
- conserve native species, and
- improve plant diversity for the Green Industry and Florida gardeners.
As part of this effort, Dr. Knox worked with the nonprofit volunteer group, Gardening Friends of the Big Bend, Inc., to develop Gardens of the Big Bend as a series of botanical and teaching gardens to showcase plants and landscaping best suited for north Florida and the greater Gulf Coast.
Dr. Knox addressed plant health by exploring plant-pest-disease-environment interactions in collaboration with plant pathologists, entomologists, horticulturists and stakeholders from Florida and throughout the southeastern U.S. Resulting research and Extension resources pertain to nursery sustainability, Integrated Pest Management (IPM), plant-pollinator interactions, and diseases/pests associated with camellia, crapemyrtle, hydrangea, magnolia and rose.
In addition, Dr. Knox supported county extension faculty, Green Industry personnel, Master Gardeners, Florida residents and other stakeholders on topics relating to nursery/greenhouse production, landscaping, plants, and gardening.
Gardens of the Big Bend for New Plants and Plant Evaluation
Using landscape plants adapted to Florida’s environment is key to reducing inputs of labor, fertilizer, pesticides and water, preventing pollution, preserving Florida ecosystems, and improving Floridians’ quality of life. New plant introductions often are not widely tested and most have not been independently evaluated in unbiased trials. Older introductions or long-used plants often have not been sufficiently evaluated for landscape performance in north Florida.
Dr. Knox has sought to identify, evaluate and promote plants that benefit Florida’s ecosystems and environment as well as the Green Industry and gardeners. As part of this effort, Dr. Knox worked with the nonprofit volunteer group, Gardening Friends of the Big Bend, Inc., to develop Gardens of the Big Bend as a series of botanical and teaching gardens to evaluate and showcase plants and landscaping best suited for north Florida and the greater Gulf Coast. The Gardens also act to conserve rare species.
General objectives of Dr. Knox’s plant evaluation program were to:
1. Identify, collect and screen taxa of interest to the Green Industry and gardening public with an emphasis on new, underused, improved or (for non-natives) non-invasive selections.
2. Formally evaluate taxa of interest to the Green Industry and gardening public, usually in cooperation with other faculty and/or at other sites to assess statewide or regional impact. Ongoing assessments include several Nandina and Ligustrum selections as well as a number of plants considered pollinator friendly.
3. Characterize the potential invasiveness (growth rate, flowering period, seed production, germination requirements) of nonnative ornamental species with the goal of identifying and promoting non-invasive selections of otherwise invasive ornamentals. Ongoing evaluations are occurring with Nandina and Ligustrum species. Collaborators are UF/IFAS faculty Sandy Wilson, Zhanao Deng and Rosanna Freyre.
4. Informally evaluate and provide outreach/teaching using Gardens of the Big Bend and other plantings (associated with objectives 1, 2 and 3) as mechanisms and sources of data for Extension programs given to the Green Industry and gardening public.
5. Evaluate and promote plants that improve pollinator health.
6. Promote and distribute taxa of new, underused, improved or noninvasive landscape plants. For example, within Florida, Dr. Knox distributed magnolias (and other plants) to the University of North Florida (Jacksonville), University of Florida (Main Campus – Gainesville and Gulf Coast REC), Harry P. Leu Gardens (Orlando), Bok Tower Gardens (Lake Worth), Fairchild Tropical Garden (Miami), Montgomery Botanical Center (Miami), Vizcaya Museum and Gardens (Miami) and Naples Botanical Garden (Naples).
Magnolia is a genus of special focus within “new plant” evaluations. Dr. Knox networked with international magnolia experts to collect and share many Magnolia species and cultivars. Throughout his 38-year career, Dr. Knox developed a large collection of Magnolia from all over the world, which can be found in the Magnolia Garden at the NFREC-Gardens of the Big Bend. This garden houses 156 unique specimens of Magnolia including 40 Magnolia species, 24 hybrids and 112 cultivars. The gardens feature the endangered Florida native Ashe magnolia (M. macrophylla var. ashei), a species only found in a few counties in the Florida panhandle. In addition, the garden is home to the five other Magnolia species native to Florida: the rare pyramid magnolia (M. fraseri var. pyramidata), cucumbertree magnolia (M. acuminata), umbrella magnolia (M. tripetala), as well as sweetbay magnolia (M. virginiana) and the familiar southern magnolia (M. grandiflora). Dr. Knox and volunteers used the Magnolia Garden to collect flowering data that was then used to develop recommendations of species and cultivars for use in north Florida nurseries and gardens.
USDA and APGA developed the Plant Collections Network (PCN) Magnolia Group for multisite conservation of Magnolia species (Magnolia Multisite PCN). The Magnolia Garden at NFREC was one of the first sites to be named part of the PCN Magnolia Group (in 2012) and is the second most southern location in North America. Furthermore, Dr. Knox coordinates with national and international Magnolia experts to propagate rare Magnolia spp. for ex situ conservation in university collections and botanical gardens. Since 2013, Dr. Knox and Gardens of the Big Bend facilitated the distribution of 22 Magnolia species and 10 new hybrids to more than 51 locations across North America.
Dr. Knox is a past president of Magnolia Society International, the international organization promoting the conservation and cultivation of Magnolia.
Rose Disease and Pest Problems
Dr. Knox collaborated with UF/IFAS and other university scientists on the discovery, development and introduction of pest/disease management tactics for use in rose IPM systems. Roses are one of the most popular ornamental flowering shrubs in the United States and had 2019 total sales valued at $168 million. Florida is the largest producer of roses in the U.S with a value of >$33 million.
Rose rosette disease caused by Rose rosette virus, an Emaravirus, has become the most devastating disease on roses in the recent years, causing huge economic losses to rose nurseries, landscape industries and home gardeners. Rose rosette virus is transmitted by an eriophyid mite species Phyllocoptes fructiphilus. The disease affects many rose species and cultivars and has been spreading through much of the wild and cultivated rose population of the Midwestern, Southern, and Eastern U.S. and threatens Florida. In addition to rose rosette disease, Dr. Knox collaborated with others on crown gall of rose and rose mosaic virus.
The Crapemyrtle Collection at the University of Florida/IFAS North Florida Research and Education Center – Quincy consists of more than 350 plants encompassing 127 taxa of Lagerstroemia and representing nine species (L. caudata, L. excelsa, L. fauriei, L. floribunda, L. indica, L. langkawiensis, L. limii, L. speciosa and L. subcostata) and hybrids. Initial plantings occurred in 2002 and taxa were added regularly since then. Crapemyrtles are in rows grouped by mature size: dwarf (<5 ft. in 5 years) plants are spaced 15 ft. apart, semidwarf (5-10 ft. in 10 years) cultivars are spaced at 20 ft., medium (10-20 ft. in 10 years) and tree (>20 ft. in 10 years) selections are spaced at 25 ft. All rows are 25 ft. apart and each row consists of crapemyrtles planted down the center of a 4 ft. strip treated regularly with glyphosate to eliminate competing vegetation. Aisles between rows are maintained as mowed turfgrass (a mix of bahiagrass and centipedegrass). Most plants are growing as multistem shrubs or trees having three to five main stems. The planting is maintained with minimal or no irrigation, fertilization, pest management or pruning. Most of the 127 taxa of crapemyrtle are represented by one plant.
Embedded in the collection is a replicated planting of 34 cultivars representing the range of mature sizes designated as semidwarf, medium and tree. Plants are laid out in a randomized complete block design with six blocks; each block consists of two rows containing a single plant of each selection. Plant spacing is 25 ft. apart within rows and 25 ft. between rows. Currently, plants, rows and aisles are maintained the same as elsewhere in the collection. Data and observations from the collection were used to develop recommendations and Florida Extension resources.
Recent research with crapemyrtle included collaboration in a multistate research project studying the biology and management of the new pest, Crapemyrtle bark scale, Acanthococcus (=Eriococcus) lagerstroemiae. This project examined the population cycles of crapemyrtle bark scale and studied best management practices including biological control options. Dr. Knox’s past research with crapemyrtle involved cooperation with UF’s Dr. Ed Gilman on impacts of pruning methods on flowering and sprouting of mature field-grown plants.
- Ph.D. Horticulture, Purdue University 1984
- M.S. Horticulture, Purdue University 1981
- B.S. Horticulture, The Pennsylvania State University 1978
2020 Sidney B. Meadows Award of Merit;International Plant Propagators' Society – Southern Region of North America. This award recognizes outstanding individuals for their contributions to the nursery industry and to plant propagation in the Southern Region of North America. It is the highest honor a member can receive.
2018 ASHS Outstanding Education Publication Award; American Society for Horticultural Science, Award recognizing the most outstanding paper published in 2017. LeBude, A.V., A. Fulcher, J.-J. Dubois, S. K. Braman, M. Chappell, J.-H. Chong, J. Derr, N. Gauthier, F. Hale, W. Klingeman, G. Knox, J. Neal, and A. Windham. 2017. Experiential nursery integrated pest management workshop series to enhance grower practice adoption. HortTechnology 27:772-781. Amer. Soc. Hort. Sci. Ann. Conf. 31 Jul.- 3 Aug. 2018, Washington, D.C.
2016 ASHS Outstanding Extension Educator Award ; American Society for Horticultural Science, Award recognizing an educator who has made an outstanding and valuable contribution to horticultural extension education for a period of 10 or more years.
2015 ASHS Extension Division Outstanding Education Materials Award: Book; American Society for Horticultural Science, Award for the hardcover and e-book “IPM for Shrubs in Southeastern U.S. Nursery Production” to editors S.A. White and W.E. Klingeman and authors S.K. Braman, M.R. Chappell, J.-H. Chong, J.F. Derr, W.C. Dunwell, A. Fulcher, F.A. Hale, W.E. Klingeman, G.W. Knox, A.V. LeBude, M.L. Paret, J.C. Neal, N. Ward Gauthier, S.A. White, J. Williams-Woodward, and A.S. Windham.
2015 Blue Ribbon Communication Award; Southern Region of the American Society for Horticultural Science Award for the hardcover and e-book “IPM for Shrubs in Southeastern U.S. Nursery Production” to editors S.A. White and W.E. Klingeman and authors S.K. Braman, M.R. Chappell, J.-H. Chong, J.F. Derr, W.C. Dunwell, A. Fulcher, F.A. Hale, W.E. Klingeman, G.W. Knox, A.V. LeBude, M.L. Paret, J.C. Neal, N. Ward Gauthier, S.A. White, J. Williams-Woodward, and A.S. Windham.
2014 Bright Idea Award; Friends of Southern IPM, The Bright Idea award goes to the Southern Nursery IPM Working Group (SNIPM) for their development of mobile information technology in the green industry. In particular, the group has developed two applications: a mobile app called IPMPro and an e-book, IPM for Select Deciduous Trees in Southeastern US Nursery Production. The Friends of Southern IPM Awards program recognizes extraordinary achievement in research, Extension and implementation of Integrated Pest Management (IPM) in the southern region of the United States. The Bright Idea Award is for a research-oriented or new idea.
2013 Fellow Award; International Plant Propagators' Society – Southern Region of North America, The Fellow Award is an honor the Region awards to its members for exceptional service and contributions to the Society and to the advancement of the field of propagation and production.
2012 Designation of Gardens of the Big Bend as a Conifer Reference Garden; American Conifer Society
2011 Designation of Gardens of the Big Bend/NFREC Magnolia Collection as part of the Multisite National Magnolia Collection of the North American Plant Collections Consortium, North American Plant Collections Consortium (collaboration of American Public Gardens Association and USDA)
2011 First Place, Poster Session - Extension Education Program Award, National Association of County Agricultural Agents Rudisill, K.R., Jackson, L.S., Stevenson, C.T., Dunning, S.O., Williams, L.L., Brasher, C.L., Knox, G.W., Hylton, T., Wells, S., Bolques, A., Miller, C., Diller, A.P., Verlinde, C.M., Saari, B.R., Dukes, M.D., and Clark, M. W. 2011. University of Florida/IFAS Extension Rain Harvesting Demonstration Trailer. National Association of County Agricultural Agents Annual Meeting. Overland Park, KS. Aug. 7-11, 2011.
2010 Porter Henegar Award, Southern Nursery Association, The Porter Henegar Award originated in 1969 as a way to honor those individuals who had made outstanding contributions to ornamental horticultural research and, more specifically, to the Southern Nursery Association, a trade association of Green Industry companies in 16 southern states. The recipient is selected annually by fellow research workers for his/her concern and work toward improving the nursery industry.
2005 Outstanding Educator of the year, Florida Nursery, Growers and Landscape Association (Presented to one individual each year).
2001 Commercial Horticulture Extension Programming Award, American Society for Horticultural Science. Co-recipient with Dr. Melvin Garber for the Georgia-Florida Green Industry Update annual series of Extension Programs.
The Team and Collaborators
NFREC Environmental Horticulture Team:
Kelly Thomas, Ag/Food Scientist II, 2018-2023.
Andrew Woodruff, OPS, 2021-2022.
Heather Kalaman, graduate student, 2018-2021.
Gardening Friends of the Big Bend, Inc. (volunteer support group) 2007-2023.
UF/IFAS Research and Extension Collaborators(since 2018):
Xavier Martini 2019-2023
Sandra B. Wilson 2002-2023
Zhanao Deng 2002-2023
Rosanna Freyre 2008-2018
Rachel Malinger 2018-2023
2021 Magnolia Society International Virtual Symposium. Zoom. Feb. 13, 2021. Member of the organizing committee and panelist.
2018 International Plant Propagators’ Society – Organizing Meeting of the China Region. Zhejiang, China. Apr. 29 – May 3, 2018. Participant in the organizing meeting of a China Region of IPPS.
2018 1st Annual World Garden Flower Show and Forum, Zhejiang, China. Apr. 29, 2018. Invited guest speaker.
2017 Magnolia Society International Annual Meeting, Malmo and Uppsala, Sweden. May 5-13, 2017. As President, I led the annual meeting, which included a scientific session in Malmo, visits to universities in Alnarp and Uppsala, and tours of gardens in Alnarp, Sofiero, Enkoping, Uppsala and Stockholm.
2017 1st Annual China NanZhao Yulan (Magnolia) Festival and Symposium, NanZhou County, Henan, China. Mar. 22, 2017. As President of Magnolia Society International (MSI), I was invited on an all-expenses-paid trip to China to open the 1st China Nanzhao Yulan (Magnolia) Cultural Festival in Nanzhao County, Henan Province. I represented MSI at the Festival’s opening ceremony and banquet. In addition, I was the keynote speaker at the First Annual Yulan (Magnolia) Symposium that day.
2016 Third International Symposium on the Family Magnoliaceae. Varadero, Cuba. Nov. 29-Dec. 10, 2016. Co-organizer, member of Scientific Committee and participant. I represent Magnolia Society International as co-organizer of this event with the Cuban Botanical Society and Planta, an organization promoting conservation of rare plants.
2015 International Symposium on Neotropical Magnoliaceae, Puyo, Ecuador. July 8-14, 2015. This symposium was organized to exchange research results, enhance the conservation and sustainable utilization of magnoliaceous plants, and promote cooperative research worldwide.
2015 Magnolia Society International Annual Meeting and tour, Wroclaw, Poland. Apr. 12-21, 2015. As President, I led the annual meeting, which included a scientific session in Wroclaw and visits to gardens in Wroclaw, Warsaw and Krakow.
2013 Guangxi Subtropical Crops Research Institute, Nanning, Guangxi, China, May 18 – 24, 2013. Consult on general nursery production procedures as well as practices specifically related to Camellia species; give presentations; tour local and regional nurseries, gardens and botanic gardens: Subtropical Crops Research Institute, Tao Flowers, Tao Camellia Nursery, Golden Camellia Park, Guilin Botanic Garden, Nanning Forestry Institute.
2011 National Botanical Garden of Cuba, Havana, Cuba, June 19 – July 2, 2011. Propagation protocols, phenology and establishing ex situ plantings of the rare Cuban endemic, Magnolia virginiana (Formal research collaboration initiated in 2010 and expected to be ongoing for several years).
2009 The 2nd International Symposium on the Family Magnoliaceae (ISFM), Guangzhou, China, May 5 – 8, 2009. Participation and poster presentations at this international symposium for scientists studying Magnolia sp. and relatives.
2009 Nanjing Botanical Garden, Nanjing, China, 10 – 11 May 2009. Discuss Magnolia sp. and nursery production research projects with Dr. Yin Yunlong of Nanjing Forestry University/Nanjing Botanical Garden, Nanjing, China.