As part of our ongoing service learning and habitat restoration component of the introductory biology courses at UHWO, my class recently started propagating cuttings of native Hawaiian plants. The students will care for their plants throughout the semester and then plant the cuttings at Piliokahe Beach as part of our dune ecosystem restoration project.
Bruce Koebele, our resident service learning coordinator and expert on Hawaiian plant propagation, visited the class to get the students started on caring for their own little keiki plant.
Step One: Prepare the Media
Our first step was to prepare a suitable potting media. We used a 1:1:1 mix of peat moss, perlite, and black cinder. This mix combines the water retention capabilities of the peat moss with the physical integrity (ie lack of decomposition) and aeration/drainage capabilities of the perlite. The black cinder provides the local ‘flavor’ of volcanic rock. Though it is not totally clear why, endemic Hawaiian plants seem to propagate better with the inclusion of cinder in the potting media.
Step Two: Prepare the Plant
Bruce brought three plants for us this semester: ‘ākulikuli (Sesuvium portulacastrum), pohuehue (Ipomea pes-caprae subsp. brasiliensis), and pohinahina (Vivax rotundifolia). All three of these plants are native to Hawai’i and are common in coastal habitats, making them ideal for planting at the Piliokahe Beach dune ecosystem.
Preventing disease in new cuttings is important. Even relatively resilient plants are more susceptible to disease when you’ve cut them open for a while. Consequently, our potting media was pasteurized and sterilized, and the cuttings themselves were washed before being planted. Once everything was all clean, the students trimmed leaves from the stem to provide underground support and cut the stem at a node. The fresh-cut stem was then dipped in a rooting hormone to encourage the cuttings to develop roots.
Step Three: Planting and Data Collection
Plants were then planted in the media-filled pots, and placed in a large plastic tub with a little water in the bottom. The tub protects the plant from desiccation until it is able to develop enough of a root system to support its water needs.
Since we are scientists, we will also be tracking the growth of the plants from now until we plant them at Piliokahe Beach. This semester, I’m propagating a pohuehue, shown at right, which is currently approximately 14 centimeters tall, and proudly sports 7 leaves. At this point, we can be certain there is no root growth. In the future, the presence of new stem growth and new leaves will indicate sufficient root growth to support new above-ground growth; however, we obviously will not uproot the plant to measure root growth.
Step Four: Future Care
The plants will live in the UHWO Biology Lab for a few weeks until they are stable enough to move home with the students. Each student will then care for their plant at home, until we bring them back to campus in October for the Piliokahe planting. Each week, the students and I will re-photograph our plants and document any changes in height or leaf number and any other notes on the health of our plants. I have full confidence that we will experience 100% survivorship and that all our little ‘ākulikuli, pohuehue, and pohinahina will soon get to start their new lives on a dune at Piliokahe Beach.