New Variegated Native Plant Selections for Landscapes: Variegated Naupaka and Oahu Sedge
Posted on Sep. 10, 2024 / Native Species, Nursery / Subscribe 0
By: Orville C. Baldos
Naupaka kahakai (Scaevola taccada) and Oahu sedge (Carex wahuensis subsp. wahuensis) are two of the most commonly used native Hawaiian plants in landscaping. Naupaka kahakai is a popular species typically used as a hedge in both coastal and inland settings. Once established, this plant is tolerant to salt, heat, wind, and drought [1]. Oahu sedge, on the other hand, is often used as a groundcover in both full sun and shaded conditions. Like naupaka kahakai, it is also drought tolerant once established and it can withstand moist conditions, wind, and some salt spray [2].
In terms of aesthetics, both plants contribute to the landscape design by providing form through their growth patterns, and texture through their distinct leaf shapes. Recently, variegated forms of both plants have been discovered, adding more choices for color and contrast. These variegated selections are slowly becoming available and could encourage people to incorporate more native plants into their landscapes.
Variegated naupaka kahakai
Two variegated selections of naupaka kahakai have been discovered recently: one on the island of Kauai and the other on the island of Hawaii. The Kauai selection does not have a specific cultivar name, while the Hawaii island selection is known as ‘Fukupaka’. Both selections feature leaves with cream to light yellow edges and splotches of light green on the middle of the leaf, creating visual contrast that make the plant stand out in the landscape. Unlike the typical upright and vigorous growth of non-variegated naupaka kahakai, these variegated selections spread horizontally and grow more slowly. If left unpruned, plants tend to mound and grow up to 3.5 feet high in 1 to 2 years. This growth habit makes them ideal for use as a low hedge or ground cover.
Figure 1. The Kauai selection of variegated naupaka kahakai is maintained as a low hedge at the UH Manoa Campus. Photo by Orville Baldos.
Figure 2. ‘Fukupaka’, a Hawaii selection of variegated naupaka kahakai maintained as a low hedge at a resort in Kona. Photo by Orville Baldos.
Figure 3. Close-up photo comparing the stems of ‘Fukupaka’ and the Kauai selection of variegated naupaka kahakai. Photo by Orville Baldos.
Propagation of variegated naupaka kahakai is relatively easy using stem or apical tip cuttings. Apical tip cuttings, at least 0.4 inches long can be rooted under mist conditions. To prepare the cuttings, harvest stem or apical pieces with clean, sterilized pruning shears. Remove the lower half of the leaves to expose the stem. Our studies have shown that applying rooting hormone (indole-3-butyric acid) at 5,000 ppm significantly improves root area, root length, and root volume of cuttings. After rooting hormone treatment, plant the cuttings in pots filled with a 1:1 by volume mix of perlite and vermiculite. Place the pots under a mist bench to prevent the cuttings from drying out. Allow cuttings to root for 30 days before potting in regular media. Place newly potted plants under shade for 1 week before moving them to full sun conditions.
Figure 4. Rooting of the Kauai selection of variegated naupaka kahakai using apical tip cuttings treated with rooting hormone. Profuse rooting was observed about 1 month after placing the treated cuttings under mist. Photo by Orville Baldos.
Variegated Oahu sedge
Oahu sedge also has a variegated selection recently discovered in cultivation on the island of Oahu. This selection has no specific cultivar name. Leaves of this selection have cream to white stripes along leaf edges, with some streaks extending to the inner portions of the leaf. This selection looks like a larger version of variegated mondo grass (Ophiopogon jaburan cv. Vittatus), offering a native alternative for similar landscape applications. Variegated Oahu sedge grows as large as the non-variegated type. To highlight its form at maturity, a planting distance of 3 feet is recommended. To showcase its cascading foliage, it can also be planted in large containers or elevated planters.
Figure 5. Variegated Oahu sedge grown as a groundcover at a resort in Kahuku. Photo by Orville Baldos.
Figure 6. Variegated Oahu sedge grown in a 15-gallon pot. Photo by Orville Baldos.
Propagating variegated Oahu sedge is primarily done by division of clumps. However, it requires extra care as it is sensitive to drying out. Shaded conditions and high humidity are essential for successful propagation. Due to these, variegated Oahu sedge is not yet widely available. Currently, our lab is working on refining single plant division protocols and exploring micropropagation techniques to increase propagation efficiency. We’ll keep you posted on any new developments.
References:
-
Elliot, D.D., MacDonald, A. & P. Gross. 2009. Scaevola taccada. Native Plants Hawai‘i website. URL: http://nativeplants.hawaii.edu/plant/view/Scaevola_sericea/. Accessed August 15, 2024.
-
Elliot, D.D., MacDonald, A. & P. Gross. 2009. Carex wahuensis subsp. wahuensis. Native Plants Hawai‘i website. URL: http://nativeplants.hawaii.edu/plant/view/Carex_wahuensis_wahuensis/. Accessed August 15, 2024.
Orville Baldos, Associate Researcher in Sustainable Ornamental Production, Department of Tropical Plant and Soil Sciences, University of Hawaii at Manoa
0 Comments