THE REGULATION OF GROWTH AND FLOWERING IN CALCEOLARIA X SPECIOSA LILJA

Low temperature (9° C) promoted flowering of Calceolaria x speciosa ‘Harting’s red’ in short photoperiods (9 h). At 12° C flowering was strongly delayed and at 15° C completely inhibited.
In long photoperiods, however, the number of days to bloom decreased with increasing temperature.
The earliest flowering was obtained at 24 h photoperiod and 15° C. However, at 15° C the difference in blooming date between plants at 24 or 16 h photoperiod was small.

There was a negative correlation between number of flowers and temperature, but a positive correlation between number of flowers and photoperiod up to 16 h.

The cultivar ‘Portia’ flowered earlier than ‘Harting’s red’. This was attributed to fewer days required to the stage of visible flower buds as well as from this stage to anthesis.

‘Harting’s red’ might be regarded as a facultative long photoperiod plant at moderate temperatures, requiring low temperature to flower in short photoperiods.
At higher temperatures long photoperiods are required.

Photoperiod extension using intermittent illumination was effective.
Four minutes of light and six minutes of dark had the same effect on flowering as continous light.

Plant height increased with increasing temperature.
Cycocel retarded flower stem elongation efficiently.
Repeated sprays with low concentraions avoided leaf burn.

With control of photoperiod and temperature, flowering and plant size can be regulated and Calceolarias, if desired, grown as a year round crop.

Symposium on Production of Potted Plants and Cut Flowers

J. Johansson

https://doi.org/10.17660/ActaHortic.1976.64.31