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Ornamental Plants

The Department of Horticulture and Landscape Architecture is committed to supporting the people and industries of Oklahoma through targeted ornamental plant research and educational programs.

Ornamental Selected Research

Proven Winners

The Proven Winners™ brand was founded in 1992 with the goal of introducing the best, most unique, high performing plants, to produce them under the highest quality standards, and to market the plants innovatively. The plants are available from just about every garden center in North America. The OSU bedding plant trial for Proven Winners™ is located at the Botanic Garden at Oklahoma State University in Stillwater, OK. These gardens have areas for the general public to become acquainted with plants that grow well in Oklahoma. Time of the evaluation and a 1 indicates the plants were dead. Flip video was also taken on the day of the evaluations.

Proven Winners research


Diatomaceous Earth, a Silica product, Applies as a Top Dress

The use of oilless substrates in greenhouse and nursery productions limits the availability of Silicon (Si) to plants. Si is the second most abundant element on earth and is present in various forms such as silicon dioxide (silica) or silicates. Plants take up Si in a soluble form such as Si (OH)3O- which is deposited in the endoplasmic reticulum, cell walls, and intercellular spaces. Si is a beneficial element for plants and helps alleviate biotic and abiotic stress. The latest research shows that plants benefit in many important ways from supplemental soluble silicon. These benefits include greater tolerance of environmental stresses, such as cold, heat, drought, salinity, mineral toxicity or deficiency, improved growth rates and resistance to insects and fungi. Plants with silicon also show a decrease in leaf and flower senescence and the shelf life of cut flowers is extended. Research into potential benefits of adding silica is fairly new and the use of it is species dependent. In our two-part study, we established different silica rates and application methods to evaluate its effects on plant growth and health of Gerbera, Rudbeckia, Dahlia, and Zinnia while under stress conditions such as drought.

Supplemental Carbon Dioxide and Its Effect on Water and Fertilizer of Ornamental Plants

Carbon dioxide (CO2) availability plays a major role in rate of photosynthesis, which is the only process for plant growth and carbon accumulation in plants. Many studies have shown that within a few centuries the CO2 level will rise up to 1500 ppm with the current developmental and industrialization trend. However, sealed greenhouses having reduced gas exchange rate, the CO2 level always drops below the ambient level of 405 ppm and suppress the potential growth of plants.  CO2supplementation is the only way of increasing CO2 in the greenhouse. In this study, effect of supplemental CO2 along with three automated tensiometer controlled irrigation treatments of 5, 10 and 15 centi bars and four fertilizer treatments 0, 3, 6, 9  g, a 3-4 months slow release formula were studied in three geranium, gladiolus, and fountain grass. In order to understand the effect of treatments, photosynthesis, transpiration, stomatal conductance, height, width, days for flowering, number of flowers and shoot dry weight were measured. The objective of the study was to understand the effect of supplemental CO2 on water and fertilizer requirement of ornamental plants in greenhouse conditions as well to analyze how plants will perform in the future when CO2 level will rise above the ambient level. Although manuscript is currently in progress, observation has shown a difference in rate of photosynthesis, number of days for flowering, and shoot dry weight between treatments.  If results are observed as expected, the study may be useful in water and fertilizer management in greenhouses supplemented with CO2.

Potted Plant Production is a Billion Dollar Market in the Plant Industry

Growers are looking for ways to increase production quality while decreasing cost and environmental impact. The use of nondestructive, optical sensors has been investigated on twelve different greenhouse crops (including poinsettia, chrysanthemum, marigold, and geranium) to improve nitrogen use efficiency, increase plant quality, develop a sampling protocol, and reduce costs associated with other sampling methods.

Fact Sheet HLA-6719 has been developed to inform growers about optical sensors. Results from the studies have shown that for all but one crop, the atLEAF chlorophyll sensor performed as well as the SPAD chlorophyll meter, which is considered the standard but costs ten times as much as the atLEAF sensor. Location of sensor readings within a leaf and not just location within a plant canopy can affect readings.  In addition, a new mobile iPhone app (Plant Nitrogen Recommendations) was developed where someone can input atLEAF, SPAD, or leaf nitrogen lab analysis values into the app for over 150 different ornamental crops. The app then gives a recommendation if additional fertilizer is needed.  Current research is looking at how many samples are needed for accurate analysis, what affect other nutrients have on sensor readings, and how timing of fertilizer application can affect sensor readings.

Contact Information

Contact Information

We invite you to learn more about our department and the many opportunities available to you. If you have any questions, feel free to contact us.

David Hillock, State Master Gardener Coordinator
David Hillock
Assistant Extension Specialist
Consumer Horticulture
358 Agricultural Hall

Mike Schnelle, Shackelford Endowed Professor of Floriculture, Oklahoma State University

Mike Schnelle
Shackelford Endowed Professor of Floriculture
Commercial Horticulture
358 Agricultural Hall

Bruce Dunn
Associate Professor
Departmental Greenhouses, Coordinator
358 Agricultural Hall