Research Matters - Flower initiation in strawberry

Nitrogen fertilisers apparently delay flowering of June-flowering strawberries if applied before flower initiation begins, yet they can promote flowering if applied after flower initiation has started.

Evidently, it is very desirable to know the state of flower initiation before applying such fertilisers.

In the experiments discussed here, plants of the cultivars 'Florence', 'Frida', 'Korona', and 'Polka' were planted in various locations in Norway in late June. They were grown on raised beds and samples of their crowns were examined under a microscope at weekly intervals.

The earliest signs of flower initiation appeared on 'Frida' on 2 September at the most southern location. 'Polka' initiated flowers about a week later, and 'Korona' a week later still. 'Florence' was very late. Flower initiation was slowest at the most northern location.

When runners were collected from these plants in July and grown in daylight at temperatures of 9 degsC, 12 degsC, 15 degsC and 18 degsC under a 12-hour photoperiod, flower initiation occurred first at 18 degsC. At 9 degsC, flower initiation was delayed by about 10 days with 'Frida', but was delayed less with other cultivars.

Ideally, the field experiment should be repeated in the UK with appropriate cultivars and locations. However, these results from Norway give an insight into the likely trends and timings that will be seen.

Dr Ken Cockshull, Associate Fellow, Warwick Crop Centre, University of Warwick

Seasonal Timing of Floral Initiation in Strawberry: Effects of Cultivar and Geographic Location by Opstad, Sonsteby, Myrheim and Heide (2011). Scientia Horticulturae 129 (1): 127-134. The contents of issues of Scientia Horticulturae and abstracts of papers are provided at

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