Abstract

Abstract
Growers within the UK rely upon relatively few poinsettia varieties, with Infinity 2.0 accounting for up to 65% of the current volume. The crop is grown for harvest from mid-November until Christmas as decoration for the domestic market and stringent specifications must be met.
Two trials are reported here:
1) Variety assessment
2) Water deficit work for plant growth control

The main objective of the variety trial was to build upon previous work, the plants were benchmarked against the current main commercial variety, Infinity 2.0. Previous AHDB research in 2015/16 assessed new poinsettia varieties coming onto the market through growth and shelf life trials, amid industry concerns of reliance upon existing varieties and stock plant maintenance. The results of these trials showed varieties such as Lenora, Ferarra, Christmas Sensation and Astro Red to be promising. The plants in the variety trial were tried on three different grower holdings across the UK.
A second aspect, the water deficit trial, was based upon industry concern regarding the reduction to two applications of important plant growth regulators (PGRs) such as chlormequat. PGRs have been critical to growers in enabling them to control crop size so attaining product specification. The removal of PGRs may hinder UK growers’ ability to meet market specification and so increase vulnerability to competition. The water deficit trial was carried out by a nursery in Lincolnshire. Therefore different approaches were investigated;
• The assessment of the potential use of remote soil moisture sensing, combined with soil moisture deficit to control stem extension (plant height) during the period of rapid stem elongation within a commercial operation, so reducing the reliance on PGRs. The formation of a transferable model of precision irrigation to maintain “optimum” moisture content, capable of being scaled-up to full production and transferable to other crops.
• To identify the substrate moisture content at which visible wilting first occurs under a range of Vapour Pressure Deficits (VPDs).