Funding for this column is provided by the ASCFG Research Committee

New Postharvest Information for Snapdragons

This research, conducted at the University of California, Davis, examined the optimal storage temperature for snapdragon vase life and the effect of ethylene inhibitors and storage temperature on gravitropism (stem bending when flowers are handled, stored or shipped horizontally).

The cultivars tested were ‘Rocket’ and ‘Potomac Pink’. Eight different temperatures, ranging from 0C to 20C, were studied. Wet and dry storage conditions were evaluated. After five days, stems were recut and vase life was recorded as the time to abscission or wilting of half of the open florets. Time-lapse photography was used to capture the gravitropic activity.

As storage temperature increased, vase life decreased. Vase life after a five-day storage period at 0C was nine days. A storage temperature of 7.5C yielded a six-day vase life and 12.5C storage resulted in a vase life of less than one day.

Though flowers held in wet storage had a longer vase life than those held at the same temperature in dry storage; flowers stored at a lower temperature (wet or dry) had a longer vase life than the wet stored flowers held at a higher temperature.

Dry storage at 0C resulted in no gravitropic bending; however, flowers stored at 2.5C and 5C, though initially bent, straightened after 24 hours. The gravitropic response was observed immediately after the flowers were placed horizontally at 20C. After 6 hours, the tip of the spike was bent at an angle of 80 degrees from horizontal.

Treatment with ethylene inhibitors prevented floret abscission, but had no effect on the negative gravitropic response. The best prevention of gravitropic bending is storage near 0C. At these temperatures, dry storage is just as effective as storage in a solution.

Celikel, F.G., J.C. Cevallos, M.S. Reid, 2010. Temperature, ethylene and the postharvest performance of cut snapdragons (Antirrhinum majus), Scientia Horticulturae. 125, pp. 429-433.

Treatment for Optimal Postharvest Performance of Viburnum

Researchers in Greece aimed to determine the optimal harvest stage of Viburnum inflorescences, evaluate the vase life when using anti-microbial compounds and anti-ethylene compounds, and assess flower opening when using a sucrose vase solution.

Viburnum flowers were harvested at three stages of opening: 10-30% open flowers, 30-50% open flowers and more than 50% open flowers. All but 4 leaves were removed from each inflorescence. Sucrose solutions of 1% and 2% were evaluated on all three stages of development, while the anti-microbial treatments (AgNO3, methanol and DICA) and anti-ethylene treatments (1-MCP) were only tested using Stage 1 flowers (10-30% open). Vase life was terminated when more than 50% of the flowers were dropped down or abscised.

Stage of development at harvest did not significantly affect vase life (7.5 to 7.9 days). However, stage of development did affect flower opening and flower abscission. Flowers harvested with more than 50% open have increased ornamental value, but at this stage, the open flowers quickly abscise leaving empty peduncles. This study suggests that Stage 1 would be optimal resulting in a gradual opening and better flower display for the period of the vase life.

Different sucrose concentrations in vase solutions neither extended vase life nor promoted flower opening. Of the anti-microbial treatments tested, AgNO3 was the only one to significantly extend vase life (8.5 days compared to a control of 6.6 days) and also reduce flower abscission. None of the anti-microbial treatments increased flower opening. A rate of 10 ml/l 1-MCP improved vase life (10 days compared to a control of 6 days) and resulted in a lower flower abscission rate.

Darras, A.I., A. Akoumianaki-Ioannidor, N.E. Pompodakis, 2010. Evaluation and improvement of post-harvest performance of cut Viburnum tinus inflorescence. Scientia Horticulturae. 124, pp. 376-380.

Practical Leaf Treatment to Improve Lily Flower Color

Lily flower quality can be negatively affected by environmental conditions such as low light and high temperatures. Maintaining optimal environmental conditions throughout the year (for forcing lilies) is expensive and energy inefficient. While some treatments have been previously suggested, they are either expensive or specific to soil type. This study, conducted in Italy, evaluated simple, inexpensive methods of improving flower quality of Asiatic lily in winter and summer.

Four cultivars were evaluated: ‘Fangio’, ‘Tresor’, ‘Brindisi’ and ‘Menorca’. Bulbs were planted in October and May. Three aqueous solutions were sprayed on the leaves until run-off. Applications were made 30 and 20 days before harvest in winter and 20 and 10 days before harvest in summer. The solutions were:
1) 2 g/l potassium sulphate (51% K2O)
2) 2 g/l sucrose
3) 1 g/l potassium sulphate + 1 g/l sucrose
Agral (0.3 ml/l) was added to each solution as a surface surfactant. Water was a fourth control treatment.

This study found improved lily flower color after a leaf treatment of potassium sulphate and/or sucrose 30 days before harvest in winter and 10 days before harvest in summer in all four cultivars tested (each cultivar responded slightly differently to the treatments but all produced positive results). Furthermore, the leaf treatment did not cause any flower or leaf damage, nor were any increased pathogen attacks observed.

In the control group, small flower buds formed at the distal end of the inflorescence failed to develop normally and failed to open in all the cultivars tested. However the K2O and sucrose leaf treatments significantly reduced flower abortion in all cultivars, especially during winter when reduced energy supply (from lower photosynthetic activity) is believed to contribute to the bud abortion.

Additionally, flower size and flower longevity were also observed to be significantly increased by the leaf treatments. The tepal length of the untreated flowers in summer was longer than the tepal length of flowers in winter; however leaf treatment resulted in winter tepal length comparable to summer tepal length.

While this treatment is effective, inexpensive and easy to apply, further research is needed to determine how treating the leaf controls flower pigment biosynthesis, flower development, ripening and senescence.

Burchi, G., D. Prisa, A. Ballarin, P. Menesatti, 2010. Improvement of flower color by means of leaf treatments in lily, Scientia Horticlturae. 125, pp. 456-460.

Megan Bame

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