Studies on Transplant Production of Dianthus caryophyllus L. and Gypsophila paniculata L. Using Different Size Cell Trays : Effects of Cell (Root Zone) Volume and Transplanting Age on Subsequent Growth and Cut Flower Quality

Experiments were conducted to evaluate the effects of cell (root zone) volume during rooting and transplanting age in two cut flower species. Cuttings of carnation, Dianthus caryophyllus L. 'Nora' and Gypsophila paniculata L. 'Bristol Fairy', were grown in trays, comprised of 406 and 128 cells pre-filled with 6 and 20 ml potting medium/cell, respectively. 'Nora' cuttings were transplanted when 20 to 50 days old at 10-days intervals, whereas 'Bristol Fairy' cuttings were transplanted when 22 to 52 days old. 'Nora' was less affected of cell volume in respect of rootball formation, i.e., 30-day old transplants with 6 and 20 ml volume capacities, the rootballs occupied 13.5 and 6.3% of the cell, respectively ; whereas in 40-day old transplants, the rootballs occupied 93.8% of the cell. Contrarily, 'Bristol Fairy' was profoundly affected that 52-day old transplants with 6 ml and 12 ml volume capacities occupied 100 and 85% of the cell, respectively. Older plants with rootballs were easier to transplant than the younger ones. However, the older ones grew slower after transplanting than the younger ones. Younger transplants had more succulent roots per plant than the older ones. The number of days from pinching to cut flower harvest in 'Nora' increased with delayed transplanting. The older transplants had longer stems, heavier flowers, and more nodes per plant than younger ones. Flower quality varied less among plants raised from the different cell volumes. Older transplants of 'Bristol Fairy' not only had longer harvesting periods, but they also had weaker shoot growth following pinching which resulted in low flower production. Younger transplants had fewer nodes per stem. Cuttings grown from 6 ml cell volume capacities required fewer days from pinching to flower harvest than those grown in 20 ml ones. Our study indicates that transplanting 'Nora' cuttings is optimal if done before rootballs are formed for production in trays. Transplants with full rootballs are sufficiently suitable in commercial production for 'Nora', whereas transplanting of 'Bristol Fairy' cuttings should be done before rootball formation occurs on account of their slow growth rate.