Shoot Growth and Flower Bud Production of Peony Plants under Subtropical Conditions

Krista C Bogiatzis,Stephen J Trueman,Helen M Wallace

doi:10.3390/horticulturae7110476

Krista C Bogiatzis, Stephen J Trueman + Show 1 more

Open Access

https://doi.org/10.3390/horticulturae7110476

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Abstract

Peony plants require temperate winter temperatures to break underground bud dormancy and allow shoot emergence and flowering in spring. This study assessed whether artificial chilling at 4 °C for 2–6 weeks could induce shoot emergence and flowering under subtropical conditions. It also assessed whether pre-treatment at cool temperatures prior to chilling, or gibberellin application after chilling, promoted shoot emergence and flowering. Artificial chilling at 4 °C for 4 or 6 weeks promoted the greatest shoot emergence. Pre-treatment at cool temperatures did not affect shoot growth or flower bud production but it improved shoot emergence from plants also treated with gibberellin. Gibberellin more than doubled the number of shoots per plant without affecting shoot length. The optimal treatment combination for shoot emergence, growth and flower bud production was pre-treatment from 20 °C to 8 °C over an 8-day period in autumn, chilling at 4 °C for 6 weeks in early winter, and treatment with 250 mL of 100 mg/L GA3, before returning plants to subtropical winter conditions. This treatment combination provided medians of 3 (0–7) and 8 (0–31) flower buds per plant in the second and third years of production, respectively. Peony flowers can be produced in subtropical climates using artificial chilling and gibberellin, allowing out-of-season market supply.

Highlights

This study assessed whether artificial chilling could enable peony shoots to emerge, elongate and flower under subtropical conditions
The study determined the effect of a cool-temperature pre-treatment prior to chilling, and a gibberellin application after chilling, on shoot emergence, elongation and flowering
Pre-treatment may, alternatively, have increased the number of effective chill-hours experienced by peony plants in the current study, pretreatment only increased the percentage of plants with emerged shoots when it was coupled with subsequent GA3 application. These results suggest that shoot emergence is slightly susceptible to artificial-chilling injury in the subtropical autumn, but that subsequent growth of the emerged shoots in winter and spring is not affected by the sudden transfer from warm to cold conditions in the autumn

Summary

Introduction

Flower development in herbaceous peonies is initiated in temperate climates in late summer from renewal buds in their perennial underground crown [2]. Peonies require exposure to a prolonged period of natural cold temperature or artificial chilling to break bud dormancy, elongate and flower in the following spring [2,5,6]. Dormancy has been considered to only be broken in temperate regions that experience freezing temperatures for 2–3 months each winter [7]. Peony dormancy can be broken in parts of Israel, Italy and southern France that only occasionally experience freezing temperatures [8]. Dormancy of herbaceous peonies has been broken in parts of New Zealand, Chile and Argentina that experience mild winters [5,7]

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