Phenological studies of Protea cynaroides (L.) ‘Arctic Ice’ following a synchronising winter pruning regime
Over the past decade, South Africa has seen an increase in the plantings of Protea cynaroides as an export cut flower. Producers rely on superior cultivars, such as P. cynaroides (L.) ‘Arctic Ice’, to secure the desired returns. The production volumes of ‘Arctic Ice’ have more than tripled over the past three years. Current cropping distribution for ‘Arctic Ice’ is restricted to two peak periods in the southern hemisphere; April-May and October-November, with low productivity outside these main harvesting seasons. Our research aimed to evaluate synchronizing pruning techniques within a biennial bearing system of ‘Arctic Ice’ to create a consistent year-round supply of flowers. We observed the vegetative and reproductive phenological events following pruning of ‘Artic Ice’ in the Western Cape region of South Africa and compared results from 2017-2019. Unpruned control plants were managed according to current commercial practices within an annual bearing system. We reported the data generated from bi-weekly tracking of shoot flushing patterns, increases in shoot diameter and number of flushes, as well as documented the flowering times obtained from harvest data. Our results showed that defined periods of active growth, similar to the control, persisted in shoots from pruned plants. Inflorescences were produced 21-27 months after winter pruning, but only on shoots that achieved a minimum number of flushes and attained a sufficient stem diameter. Synchronised plants resulted in increased production volumes per season, yet most flowering remained clustered within the two commercial harvest peaks similar to that observed for control plants. The flowering outcomes, as well as the estimated time (days) from prune to harvest (DPH), was established using vegetative shoot characteristics as predictor variables. We determined that thorough characterisation of shoot regrowth from prune to harvest, locality specific inferences, and shoot phenology can aid in the understanding and management of commercial ‘Arctic Ice’ production systems to extend product availability. Naomi Hattingh completed her MSc research project at Stellenbosch University, South Africa, under the supervision of Dr. Lynn Hoffman, Dr. Eugenie-Lien Louw and Mrs. Caroline O’Brien. This project investigated regrowth and flowering behaviour in Ayoba® ‘Arctic Ice’ and the manipulation of flowering time through various horticultural techniques.
Naomi Hattingh won the ISHS Young Minds Award for the best oral presentation at the XIV International Protea Research Symposium in the Canary Islands (Spain) in March 2022.
Miss Naomi Hattingh, Future Fynbos (Pty) Ltd, Somerset West, South Africa, e-mail: firstname.lastname@example.org
The article is available in Chronica Horticulturae