2019 ASHS Annual Conference

In Hawaii, the use of native plants as ornamentals has increased in the last 30 years due to state legislation promoting its use in state-funded landscaping projects. Despite the increase in the use of native plants in urban areas, the availability and variety of horticultural selections still continue to be limited. Pa’uohi’iaka (Jacquemontia sandwicensis) (Convolvulaceae) is an endemic coastal plant that has been used as a groundcover in landscaping. In the wild, morphological variations in Pa’uohi’iaka exist, making it a potential species for developing new selections. Due to its pre-formed roots, the plant is relatively easy to propagate. Three to four node stem cuttings is often recommended for its propagation. However, the use of single-node stem cuttings might be useful for propagating more plants with less planting material. This study aimed to characterize the rooting response of the six Pa’uohi’iaka accessions and to determine the feasibility of propagating from single-node stem cuttings. Four-node and one-node stem cuttings from each accession were prepared and planted in pots filled with a 1:1 perlite and vermiculite mix. Each treatment had ten stem cuttings per pot and was laid out as a split-split-split plot experiment replicated four times. The season of propagation served as the main plot, accessions served as the split-plot and the number of nodes served as the split-split plot. Stem cuttings were allowed to root under mist irrigation set to open for ten seconds every six minutes. Root length, root number, percent rooting, number of shoots and number of leaves retained were measured 21 days after planting. Results indicate that, in general, four-node stem cuttings have a significantly higher number of roots and percent rooting compared single-node cuttings. In both four-node and single-node cuttings, Ahihi-Kinau exhibited the highest number of roots and shoots among the six accessions. The use of single node stem cuttings was feasible only to Ahihi-Kinau and Shidler College accessions. Glabrous leaf accessions (Ahihi-Kinau, Shidler College and Lyon Arboretum) exhibited a significantly higher number of leaves retained leading to favorable rooting response. Pubescent leaf accessions (McGregor, Puhala Bay and South Point) had poor leaf retention and rooting. The experiments indicate that the presence and type of leaves, as well as stem cutting length, are crucial in successful rooting of Pa’uohi’iaka.