FreezePruf: Spraying for Freeze Protection

FreezePruf is a commercial-ly available product recently marketed to improve both freeze avoidance and tolerance. The developer promotes up to a five-degree protection for flowers, leaves and fruit, though the level of protection varies with plant material. This study, carried out at Oklahoma State University, aimed to evaluate FreezePruf on tomato leaves, pepper and celosia seedlings, tomato fruit and bermudagrass crowns and stolons. (For the purposes of The Cut Flower Quarterly, this review will focus on the celosia experiments.)

Three-week-old ‘Kewpie Orange’ celosia seedlings were sprayed with deionized water (control) or DI water and FreezePruf 24 hours prior to low temperature exposure. The experiment took place in a convection chamber, which was cooled rapidly to 0°C, then cooled at 2°C per hour to -20°C.

No significant difference was observed in the mean freezing temperatures of celosia seedlings sprayed with water (-6.1°C) or FreezePruf (-6.2°C).

Anderson, J.A. 2012. Does FreezePruf Topical Spray Increase Plant Resistance to Freezing Stress? HortTechnology, 22(4):542-545

Hydrating Dried Tuberous Roots of Ranunculus

Ranunculus asiaticus may be grown from seed or from dried tuberous roots. Plants grown from roots flower faster and more profusely. Hydrating the dried roots prior to planting is common practice to improve uniformity and to facilitate fungicide application. This research evaluated how hydration temperature effects plant growth.

Three experimental designs were carried out. In Experiment 1, roots were submerged in tap water at 5, 17, 23, or 35°C for 24 hours, followed by a 5-minute soak in a copper sulfate biocide. In Experiment 2, roots were submerged in tap water at 5, 10, 17, 20, 25, 30, or 35°C for 24 hours, followed by a 5-minute soak in a copper sulfate biocide. In Experiment 3, roots were submerged in tap water at 5, 15, 25, or 35°C for 24 hours, followed by a 5-minute soak in a copper sulfate biocide. Evaluation criteria included percent survival, plant height, shoot dry weight, number of flower stems, and a visual quality ranking assigned on a 1-5 scale.

The hydration model indicated that water uptake was faster in warmer water. At room temperature, soaking for 24 hours before potting was considered sufficient to hydrate the tubers. In all three experiments, percent survival increased with hydration temperatures up to 20°C (15°C for Expt. 3) and decreased as hydration temperatures increased beyond that.

Considering the other evaluation criteria, this study suggests water temperature monitoring is an important factor when hydrating R. asiaticus and should be maintained between 15 and 25°C. Determining the temperature of your water source is important, since tap water may be cooler and other sources (such as water in a greenhouse) may be warmer.

Cerveny, C.B., W. B. Miller, T. Bjorkman and N.S. Mattson. 2012. Soaking Temperature of Dried Tuberous Roots Influences Hydration Kinetics and Growth of Ranunculus asiaticus (L.), HortScience, 47(2):212-216.

High Tunnel vs. Field Production of Some Cut Flowers

High tunnels are relatively low-cost structures often used for season extension, rain protection, and reduced disease. With a lower daily light integral (compared with field production), cut flowers typically develop significantly longer stems in high tunnels. Researchers at Purdue University evaluated 10 specialty cut flower cultivars in field and high tunnel production. They compared weekly yield and quantified other differences that could be attributed to the different production systems.
Cultivars evaluated were: Antirrhinum ‘Rocket Red’, Celosia ‘Chief Red’, Dianthus ‘Amazon Neon Cherry’, Matthiola ‘Katz Lavender Blue’, Zinnia ‘Benary Giant Scarlet’, Dahlia ‘Karma Thalia Dark Fuchsia’, Eustoma ‘Mariachi Blue’, Helianthus ‘Sunrich Yellow’, Antirrhinum ‘Potomac Orange’, and Helianthus ‘Premier Lemon’.

Significantly longer stems were observed on the plants grown in the high tunnel for these cultivars: Antirrhinum ‘Potomac Orange’ and ‘Rocket Red’, Eustoma, Matthiola and Zinnia. The number of stems harvested per square meter was significantly higher for  Antirrhinum ‘Potomac Orange’, Celosia, Dianthus and Zinnia. While the stem caliper of Matthiola and Zinnia was greater, stems of ‘Potomac Orange’ was smaller in the tunnel.  The small caliper stem combined with the longer stem length resulted in stem support problems. Reduced time to harvest was also observed for Celosia, Dahlia, Dianthus and Helianthus ‘Premier Lemon’.

While this study demonstrated several benefits of high tunnel production over field production, it also noted that the benefits are cultivar-specific, suggesting a greater need for further research on additional specialty cut flower cultivars.

Ortiz, M.A., K. Hyrezyk and R.G. Lopez. 2012. Comparison of High Tunnel and Field Production of Specialty Cut Flowers in the Midwest, HortScience, 47(9):1265-1269.

Petal Blackening and Flower Opening in Lotus

Previously, research has looked at the effect of exogenous ethylene on petal blackening in cut lotus flowers. This study aimed to evaluate other hormone classes: auxin, cytokinin and gibberellin with a goal of delaying early petal blackening and promoting bud opening.

The flower buds of Nelumbo nucifera spp. Nucifera, cv. Saddabutra, were harvested at the normal commercial stage and held at room temperature. Vase life was defined as the period until half of the visible petals showed black patches. The flower was defined as “open” if the petals at the tip leave an opening. Two treatment methods were used for the application of the hormonal chemicals. In Experiment 1, the chemicals were included in the vase water at the onset and not replenished. In Experiment 2, the chemicals were applied as a 3- to 12-hour pulse treatment.

The study found that the hormone treatments tested had no effect on bud opening. However, pulse treatments of GA3 and thidiazuron showed promising results with delayed petal blackening. Interestingly, the effect seemed to be dependent on the time of year indicating a seasonal cultural effect.

Imsabai, W. and W.G. van Doorn. 2013. Effects of auxin, gibberellin, and cytokinin on petal blackening and flower opening in cut lotus flowers (Nelumbo nucifera), and Technology Postharvest Biology, 75:54-57.

Megan Bame

Megan Bame is a freelance writer in Salisbury, North Carolina. Contact her at [email protected]