Japanese flowering cherries (Prunus serrulata) were due to be banned from sale in the Auckland Region from 1 September 2022, under the Auckland Council Regional Pest Management Plan.
There is some evidence that the double-flowered cultivars are sterile, where the stamens and pistils have been replaced by an extra row of petals. NZPPI contracted Plant & Food Research in 2021 to do a floral study looking at seven Japanese cherry cultivars popular in the Auckland market.
Two cultivars - Prunus 'Kanzan' and Prunus 'Shimidsu Sakura' - are sterile and have been granted an exemption from the ban. The ovary and styles in the flowers are replaced by leaflets and their pollen is largely unviable.
Prunus 'Tai Haku', Prunus 'Kiku Shidare Sakura', Prunus 'Shirotae', Prunus 'Amanogawa' and Prunus 'Ukon' have been granted interim exemption to 1 September 2023 while more work is done. The study found most of the male reproductive structures in 'Ukon' lacked anthers, and of those present, they had less than 1% pollen viability. Further work will be done in Spring 2022 to look at stigma receptivity.
See attached letter below from Auckland Council which outlines the exemptions.
The news comes a little too late for some nurseries, who have already stopped producing Prunus serrulata varieties for the Auckland market in anticipation of the ban.
NZPPI is hoping that other cultivars can be included in the 2022 Spring testing. Flowering cherries are a popular street tree in urban subdivisions and developments as well as home gardens. There are over 400 varieties around the world and it is likely there are qute a few more varieties present in New Zealand which are not currently being commercially produced. Hopefully some of these could turn out to be suitable for the Auckland climate, be sterile, and help plug the gaps for Aucklanders.