Two experiments between 1995 and 1997 studied the effects on bud developmen
t through to flowering of lifting bare-root rose plants of cv. Warm Wishes
from October to December and potting them immediately or at intervals from
February to July after cold storage. In both experiments the times of four
key morphological stages, bud burst, first expanded leaf, flower bud and bu
d showing colour, were recorded on terminal shoots. There were no significa
nt effects of lifting date on the time from potting to any morphological st
age and in the first experiment the most appropriate storage temperature wa
s 0 degrees C. The major effect on time to all four morphological stages wa
s the time of potting, with later potting resulting in progressively shorte
r intervals to each stage. For crops potted in the year in which they flowe
red the most appropriate of the environmental scales considered for describ
ing the period from potting to buds showing colour was day-degrees >4 degre
es C. On average, crops required 772 day-degrees >4 degrees C from potting
to bud showing colour and 543 day-degrees >4 degrees C from the first expan
ded leaf to the same stage. Using meteorological data from 1989-1998, simul
ations of the time to buds showing colour were run for crops potted at the
beginning of each month from February to July. These enabled effects of yea
rly variations in temperature on predicted marketing dates to be estimated.
They show that, on average, buds were predicted to show colour between 17
June (February potting) and 28 August (July potting) and that over the ten
years the range of predicted flowering dates was 34, 23, 17, 18, 13 and 17
d from potting at monthly intervals from 1 February to 1 July respectively.
This model provides a framework for scheduling potting dates to extend the
season and maintain continuity of supply of plants at the optimum stage fo
r marketing.