Effects of Fertilizer Rate and Media Formulation on Vertical Growth and Basal Shoot Production of Transplanted Tissue-cultured Plugs of Dracaena 'Ruth Luka'

Dracaena ‘Ruth Luka’ is a new introduction by the Hawai’i Export Nursery Association. It was discovered in Mauritius in 2004, as an unnamed, cultivated plant.  DNA analysis has confirmed that it is a Dracaena but is a different species from other Dracaena selections and varieties currently in the trade. No recommendations on appropriate potting media or fertilizer programs for this plant have been published. In this experiment, 2-month-old single-stemmed tissue-cultured plugs were transplanted into 15.2 cm standard pots filled with one of three potting media: volcanic cinders and coco-chips (2:1, v:v), coco-peat and parboiled rice hulls (2:1, v:v), or sphagnum peat and perlite (1:1, v:v). All media were supplemented with micronutrients and either lime or gypsum as appropriate. Additionally, these media were supplemented with either of two rates of a slow-release (5-6 month) 15-6-12 fertilizer formulation, for a total of six treatments. Plants were grown in a shaded greenhouse and irrigated automatically. After six months, plants grown in peat-perlite media supplemented with the lower of the two fertilizer rates (7.6 g/pot) had taller central stems than plants grown in any other fertilizer/medium combinations. Plants grown at the lower fertilizer rate were more likely to grow upright, whereas plants grown at the higher rate (17.3 g/pot) often leaned or fell over. Plants grown in all of the media and fertilizer combinations were inclined to produce from one to six basal shoots after the original transplant stem length exceeded 20cm in height. All of the tested media/fertilizer combinations could produce a marketable plant of ‘Ruth Luka.’ It appears that the lower fertilizer rate is adequate for production of this cultivated variety, regardless of potting medium.