EFFECT OF LOW-TEMPERATURE TREATMENTS ON FLOWERING IN 3 CULTIVARS OF HEBE COMM EX JUSS

The genus Hebe is mainly native to New Zealand, and a number of specie s and cultivars are used as ornamental garden and balcony plants in ma ny countries. The ornamental value is increased by controlled flowerin g. In this experiment chilling (15.5/9.5 degrees C or 9/3 degrees C da y/night) treatments of different durations (0, 3, 6, 9 or 12 weeks) we re tested on three cultivars of Hebe, 'Inspiration', 'Variegata' and ' Waikiki'. After chilling the plants were forced under 25/19 degrees C conditions for 12 weeks. Flowering was promoted by the chilling treatm ents, and complete flowering in the apical shoots occurred after 9-12 weeks chilling in 15.5/9.5 degrees C for 'Inspiration' and 'Waikiki'. Increased flowering of 'Variegata' (75% of the plants) was observed af ter 12 weeks 15.5/9.5 degrees C treatment followed by forcing. The mor e induced plants had become under the chilling treatments, the shorter time was necessary under the forcing conditions for flower developmen t. With all cultivars, cool conditions were more effective for flower induction than cold conditions. Flowering was more rapid where the low temperature conditions lasted longest. Larger 'Inspiration' plants we re induced more readily than the smaller plants. The importance of siz e of the plants at the start of chilling was tested for 'Inspiration', where plants with 22 nodes flowered after shorter time under forcing conditions than plants with 12 nodes.