Each semester, my intro biology and intro botany students at UH West O’ahu participate in service learning events at sites throughout the Ewa Plain and the leeward coast of O’ahu. New this semester, my botany students also get to learn about growing and caring for native Hawaiian plants by propagating their own cutting, which will be planted later this semester at Piliokahe Beach.
Today, Bruce Koebele (who coordinates all of our service learning events, and who manages his own website dedicated to native Hawaiian plant propagation and care) visited my botany class to walk us through the steps for propagating cuttings of three endemic Hawaiian plants.
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. We filled a standard small plastic plant pot with the potting media and then thoroughly soaked it in water to prepare for planting.
Bruce brought three plants for us: pohuehue (Ipomea pes-caprae subsp. brasiliensis) ‘akulikuli (Sesuvium portulacastrum), and pau o’hi’iaka (Jacquemontia ovalifolia subsp sandwicensis). All three of these plants are endemic to Hawai’i (meaning they are found only in the Hawaiian Islands) 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. Plants were then planted in the media-filled pots, and topped with a plastic water bottle. The water bottle 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. My plant, the little ‘akulikuli shown at right, is currently approximately 13 centimeters tall, and proudly sports 62 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. 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 ‘akulikuli, pohuehue, and pa’u o hi’iaka will soon get to start their new lives on a dune at Piliokahe Beach.