Caleb Spall, is an M.S. student at Michigan State University and is currently investigating how light quality, DLI, and photoperiod influence flowering and morphological responses of greenhouse-grown specialty cut flowers during the young plant and finishing stages. Consumer and market demand for locally sourced, sustainably produced fresh specialty cut flowers continues to increase in the U.S. Growers across northern latitudes cannot produce specialty cut flowers in field or high tunnel cropping systems year-round due to the extreme temperatures and low DLIs characteristic of winter months. As a result, they must utilize greenhouses to produce high-quality specialty cut flowers during the winter to satisfy demand. The results of this research could be adapted into cultural guidelines for Midwestern and northern growers who are already utilizing or plan to utilize greenhouses for year-round specialty cut flower production.

Anthony Soster, is an M.S. student at Michigan State University and is currently investigating how daily light integral (DLI), day and night temperature, photoperiod, and plant growth regulators impact production time, leaf unfolding rate, excessive stretch, and flower development of succulents. Consumer demand for potted succulents continues to increase in the U.S. due to their diverse colors, forms, and flowers. However, when grown in greenhouses located in Northern latitudes, the production cycle of some succulent genera can be greater than 16 weeks, especially during winter months. Unfortunately, little research based information is available regarding how temperature, light, and photoperiod interact to and potentially reduce production time and promote flowering. The goal of this research is to develop models and identify critical photoperiods for several genera and cultivars of commonly grown succulents to reduce production costs and increase profitability. Additionally, we are investigating if a pre-shipment high rate PGR substrate drench can effectively reduce excessive stretch under low light environments such as consumer homes and offices.  

Post-doctoral research associate Yujin Park at Michigan State University investigates how the radiation spectrum of sole-source LED lighting influences growth and development characteristics of floriculture transplants.

A new method of producing floriculture transplants is indoors using light-emitting diodes (LEDs). However, one of the challenges and opportunities of implementing this new production technique is to determine the radiation spectrum to obtain desired plant responses. The quality attributes of floriculture crops, including plant size, leaf color, growth habit, and flowering time, can all be modified by the radiation spectrum, and also plant responses can vary among plant species and cultivars.

Yujin’s research is investigating how different spectral and intensity combinations from blue (400-500 nm), green (500-600 nm), red (600-700), far-red (700-800 nm), and white LEDs interact to regulate photosynthesis, plant growth, and flowering responses on a broad range of floriculture crops. The results from previous experiments identified the potential benefits of including far-red radiation in the lighting spectrum, including increased seedling growth, regulation of plant size, and earlier flowering. We also learned that far-red radiation combined with a moderately high intensity of blue radiation can produce compact plants while accelerating flowering time in some species. To best utilize sole-source LED lighting technology in floriculture transplant production, this research will further generate new science-based information on the kinds of plant responses and benefits growers can achieve by managing the radiation spectrum.

Kellie Walters, a Ph.D. student at Michigan State University, is working on the production, flavor and color enhancement of leafy greens and culinary herbs in controlled environments. She is evaluating how light intensity and quality, short wavelength radiation, carbon dioxide, and temperature interact and influence leafy green and herb flavor, volatile oil content, anthocyanins, growth, and development. Additionally, she has several side projects that include 1) quantifying the impact of carrier water alkalinity and air temperature at application on the efficacy of various plant growth regulators (PGRs) including ethephon and 2) determining the photoperiodic flowering responses of several specialty crops. 

The plant growth regulator (PGR) ethephon [(2-chloroethyl) phosphonic acid] breaks down to release ethylene (C₂H₄) and can be sprayed on floriculture crops to reduce cell elongation, inhibit internode elongation, reduce apical dominance, increase lateral branching, and abort flower buds and flowers. However, the efficacy of ethephon applications is influenced by a variety of environmental and cultural factors. For example, As pH or ambient temperature increases, ethephon efficacy decreases. This is due to ethephon breaking down into ethylene more quickly before it is absorbed by the plant. Since carrier water alkalinity affects solution pH, Kellie is quantifying how ethephon efficacy is influenced by carrier water alkalinity and air temperature at application. With increased efficacy comes the potential for lower chemical inputs, increased uniformity, and higher quality plants. Kellie is also determining the photoperiodic flowering responses of several foliage annual plants, herbs, and hop vines. Growers are increasingly incorporating foliage annuals into mixed combination planters due to their brightly colored or patterned leaves. However, the flowers of these foliage annuals are often unattractive and stall the desired vegetative growth. Therefore, our goal is to provide photoperiodic lighting recommendations to prevent flowering in foliage crops and herbs and enhance cone production of hop vines grown in controlled environments.

Melissa Muñoz Agudelo, Ph.D. student at Clemson University.

Botrytis cinerea is the fungal pathogen responsible for Botrytis blight in several crops including commercial cut roses. This disease is usually acquired during the production stage, but disease symptoms are more often seen in the post-harvest, especially when infected flowers are exposed to high humidity conditions during transportation. Fungicide applications as single-site or multisite products have been one of the main strategies for Botrytis blight management. However, during our previous research we were able to prove that several B. cinerea isolates are resistant to different fungicide modes of action, which means a challenge for disease management especially considering that environmental conditions in the commercial greenhouses like leaf wetness, temperature and relative humidity are favorable for disease development most of the time.

Current research focusses on the evaluation pre- and post-harvest applications of calcium in roses and assessment of different BCAs as management strategies for Botrytis blight alternative to the traditional fungicides. The integration of this strategies as part of an integrated disease management might allow a better rotation of fungicides and hopefully reduce Botrytis blight incidence and severity.

Mary Vargo is an M.S. Student at Clemson University and is currently evaluating stock plant management techniques on the effects of post-harvest flower development of Impatiens xhybrida. One of the principle strategies for producing many cuttings from stock plants involves the weekly application of ethephon, however, high rates of ethephon can cause significant delays in flowering for cuttings grown in the post-harvest environment.

We are assisting stock plant growers by evaluating daily light integral levels, ethephon rates, and cutting harvest position on the stock plant to create guidelines for producing high quality, uniform cuttings that flower in 5-6 weeks in the post-harvest production. We are also creating a bud meter that tracks flower development from visible bud to open flower at various temperatures so growers can utilize this resource as a means to keep the crop on schedule for the timely success of uniform flowering crops.

Stephanie Cruz is a M.S. student at the University of Florida currently evaluating growth, development, and quality of compact tomato and pepper plants to support consumers interested in indoor and patio gardening. An increasing number of compact fruiting vegetables are becoming available for home gardening, which has been ranked as one of the fastest-growing trends in horticulture. However, evaluations are limited, especially under the reduced light intensity and different light spectra with sole-source lighting compared to sunlight. Her research is focused on identifying resilient cultivars that are compact and high yielding, are not susceptible to physiological disorders commonly observed indoors, and can thrive with minimal inputs in order to ensure consumer success.

Marlon Retana Cordero is an M.S. student at the University of Florida currently evaluating the effect of 1) photoperiodic control and production cycle on yield and quality of greenhouse-grown ginger and turmeric plants; 2) plant density and container size on profitability; and 3) kaolin spray application as a strategy to reduce radiation stress in open-field ginger and turmeric production. Results from his research will address an emerging area of interest among local growers and consumers and will also provide information to improve our understanding about sustainable production practices in the southeastern United States.

Matias Yegros is a Ph.D. student at the University of Florida currently evaluating the use of indoor farming technologies to improve ex-vitro acclimatization of high-value tissue culture plants. Although indoor propagation environments offer significant opportunities to improve rooting and growth of hard-to-propagate plants, it has an increased cost to growers that needs to be offset by enabling shorter production cycles, increased rooting success, and improved quality and predictability compared to conventional propagation methods. His research is focused on evaluating environmental interactions that can help maximize indoor propagation efficiency. The overall goal of his Ph.D. dissertation is to help growers make informed decisions and maximize the return on investment when using indoor propagation environments.

Melissa Muñoz Agudelo, M.S. en route to Ph.D student at Clemson University, is currently evaluating traditional and alternative management strategies for Botrytis control in cut rose production greenhouses. Botrytis cinerea is a significant problem affecting cut rose production in both pre-and post-harvest conditions which leads to losses for both growers and wholesalers. One of the principal strategies for disease management is fungicide applications including multisite and site-specific fungicides. However, the development of resistance is becoming more problematic especially in the case of the site-specific fungicides, making them less effective.

We are helping growers by evaluating fungicide resistance development, monitoring cultural practices and environmental factors that are associated with disease development to create a risk model that lead to better strategies for fungicide applications and we are evaluating alternative management strategies for disease management using post-harvest calcium dips.

Maria Fernanda Trientini, an M.S. student at the University of Florida, is researching the use of Controlled Release Fertilizers (CRF) in hydroponic systems.  Hydroponics are being promoted for urban homeowners, and is an expanding market to sell transplants and growing systems. However, nutrient and pH management are too complex for most consumers. Nowadays, new CRF materials are available in the US. In this project, Dr. Fisher and Fernanda aim to simplify nutrient management in hydroponics by formulating a standard dose of blended CRF per gallon per month. This would improve consumer success with ‘grow your own’ vegetables. 

M.S. student at Clemson University, Jiwoo Park, is working on growing petunias for improved consumer performance.

Consumer performance is critical to the success of greenhouse businesses. In recent years, greenhouse growers have reduced the amount of fertilizer applied to their spring bedding plant crops. This has resulted in concern about the performance of these plants once the consumer has purchased them. This experiment was designed to determine the effect of different fertilizer delivery methods and fertilizer concentrations on the growth of petunias (Petunia x hybrida) in the consumer environment. We focused on three fertilizer delivery strategies: Constant Liquid Fertilization Program, Controlled Release Fertilization Program and Post-Production Fertilizer Pulse Treatment. This study also examines the fertilizer cost efficacy associated with different fertilizer application techniques.

M.S. student at Clemson University, Katherine Bennett, is investigating calcium as an alternative to fungicides for Botrytis control.

Petunia Flower Meltdown, or rapid necrosis of petunia flowers, is a problem during transport of flowering plants from the greenhouse to retail locations. This phenomenon is a result of Botrytis infection in the greenhouse, and the disease expression occurs when the plants are placed into a humidity environment during transport. We are looking at alternative compounds for control as fungicides are becoming less effective due to resistance development. Initial studies demonstrated the potential value of calcium to inhibit Botrytis infection in petunia flowers. So, we are conducting experiments to determine the best strategies for applying calcium to reduce the postharvest losses that occur due to Botrytis infection.