Zinc Improves Gladiolus Cut Flowers

Researchers in Pakistan evaluated the postharvest effects of zinc applied preharvest in gladiolus. Previous research has shown that zinc concentrations in biological systems is higher than other micronutrients. Zinc nutrition may play a role in a plant’s ability to cope with oxidative stress, one of the primary factors leading to early senescence in ethylene-insensitive cut flowers.

Potted Gladiolus hortulanus cv. “White Prosperity” were raised under greenhouse conditions. Zinc sulphate was applied at rates of 0, 2, 4, 6, 8 and 10 mg/kg.  It was noted that the soil had a starting zinc content of 0.85 mg/kg. Spikes were harvested at 2-3 open florets and placed in distilled water for vase life evaluation.

Plant growth was improved with zinc treatment compared to the control. The highest values for leaf area, spike length and fresh weight were achieved at a rate of 6 mg Zn/kg. The highest flower count and largest flower size was also observed at 6 mg/kg, while a treatment rate of 8 mg/kg brought about the earliest flowering. The percentage of opened florets and vase life duration were greatest at 6 and 8 mg Zn/kg.

With symptoms of mild toxicity exhibited at 10 mg Zn/kg, the study suggests zinc applied to the growing media at a rate up to 6 mg/kg produce the best results with improved growth and quality. The extended vase life was attributed to enhanced biochemical attributes, membrane stability and increased antioxidative enzyme activity.

Saeed, T., I. Hassan, G. Jilani, and N.A. Abbasi. 2013. Zinc augments the growth and floral attributes of gladiolus and alleviates oxidative stress in cut flowers. Scientia Horticulturae. 164:124-129.


Effective Fungicides for Gladiolus Rust

Gladiolus rust, Uromyces transversalis, is a pathogen of quarantine significance in the Unites States. In 2006, this disease was introduced in California and Florida. Detection of the fungus on two Florida farms resulted in mandatory and costly quarantine and eradication. The disease, which can result in total crop loss, has become endemic in several production areas in Mexico. This study, a collaborative effort between Mexico and the United States, was a preliminary investigation to determine the best fungicide active ingredients for disease management. Sixteen active ingredients were applied as individual products, as combinations of two products, and as rotations of different individual products or combinations.

All trials were conducted in commercial gladiolus fields naturally infected with U. transversalis. Fungicides were applied at the third-leaf stage and applications were made four times at 2-week intervals. The control was untreated.

All the products tested provided some level of rust management. Those that provided “very good to excellent” management included triazole, strobilurin and SDHI (succinate dehydrogenase inhibitor) fungicides. The most effective disease management was achieved by using combinations of a triazole fungicide with a strobilurin fungicide and rotating to a different product or combination of products.

Valencia-Botin, A.J., S.N., Jeffers, C.L. Palmer, and J.W. Buck. 2013. Fungicides used alone, in combinations, and in rotations for managing gladiolus rust in Mexico. Plant Disease. 97:1491-1496.


Water and Nitrogen Needs of Gladiolus

While too much water for gladiolus may cause bulbs to rot and slower growth, insufficient water results in shorter stems, smaller flowers and tip burn. Researchers in Brazil evaluated irrigation management and optimal nitrogen fertilization of greenhouse-grown Gladiolus x grandiflorus L., ‘White Friendship’.

Irrigation treatments consisted of five levels of water replacement: 50%, 75%, 100%, 125% and 150%. For this experiment, the water tension equivalent to soil moisture at field capacity was defines as 6 kPa. Five nitrogen concentrations (from urea) were also evaluated: 0, 30, 60, 90 and 120 mg/dm3. The nitrogen doses were divided into three applications at 20, 31 and 40 days after planting.

The maximum number of leaves was observed at a water replacement level of nearly 150%, while maximum plant height and maximum floral stem length occurred at around 130%. While floral stem length was unacceptable (for the Brazilian market) at a water replacement level of 50% (49.87 cm), all treatments with a rate of at least 75% resulted in stem lengths within commercial standards (95-135 cm). The floral spike length linearly increased as water replacement level increased. The maximum number of flowers and highest flower diameter were observed at around 130%. The shortest time to flowering (62 days) was also observed at a water replacement level of 130%.

The only reported significant response to nitrogen fertilization was for floral stem dry mass. Dry mass was almost 20% less in stems with no applied nitrogen compared to those receiving 120 mg/dm3.

de Andrade Porto, R., M. Koetz, E.M. Bonfim-Silva, A.C. Polizel, T.J.A. da Silva. 2014. Effects of water replacement levels and nitrogen fertilization on growth and production of gladiolus in a greenhouse. Agricultural Water Management. 131:50-56.

Megan Bame

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