Native Hawaiian Garden (7722)

ʻOhe makai or ʻOhe kukuluaeʻo (Polyscias sandwicensis; formerly Reynoldsia sandwicensis) – What time is it?

Both ‘ohe makai and wiliwili (Erythrina sandwicensis) are large endemic trees most common in the drier regions of Hawai‘i's dry forests and shrublands. (In contrast, ‘ahakea and olopua are more prevalent in the wetter areas of Hawai‘i's drylands.) As the hot dry summer approaches, both trees shed all their leaves to conserve water. Later, in the fall with cooler wetter weather, the two species produce a flush of new leaves. However, the cues ‘ohe makai uses to determine 'Winter is coming' appear to be quite different from the cues used by wiliwili. This difference in telling time was not apparent to me until I started propagating and growing the two species in a nursery and garden environment. What I discovered is that regardless of how often I watered my young ‘ohe makai they invariably dropped all their leaves during the summer and became dormant. In contrast, if I watered my young wiliwili, particularly those I had in the nursery, they retained (most of) their leaves and continued to grow throughout the summer. From this observation, I concluded that ‘ohe makai must be using some environmental cue other than soil moisture to help it 'decide' whether it should drop its leaves or put out a new flush of growth. I hope that my observations will spark the curiosity of a young researcher who will conduct the proper experiments needed to determine what environmental cue(s) ‘ohe makai is using to tell time.

Habitat & Appearance: A medium to large tree with thin bark, soft wood, and thick sometimes twisted branches, that is endemic to dry (occasionally mesic) forests and shrublands on Ni‘ihau, O‘ahu, Moloka‘i, Lāna‘i, Maui, and Hawai‘i. ‘Ohe makai is curiously absent from Kaua‘i, the Hawaiian island with the greatest number of native Polyscias species. ‘Ohe makai has glossy pale green pinnately compound leaves that it sheds during the summer months to conserve water. Small greenish-yellow to orange-purple flowers develop in clusters on short stalks. These mature into small soft purple fruits, each containing several flat seeds.

Most of the ‘ohe makai I have seen over the years look similar to the one in my photograph to the right. However, some ‘ohe makai grow into giants with a form resembling the introduced monkey-pod tree (Pithecellobium saman) — I have seen these in Kanaio, Maui — while others grow into quite short and very wide trees (look for this form in Kānepuʻu, Lānaʻi).

Wait until these nearly-ripe fruits are soft and purple before collecting them (Photograph courtesy of David Eickhoff CC BY-NC-SA 2.0). Seedling. Mature tree in North Kona, Hawai‘i. (Header photograph courtesy of G.D. Carr ©.)

‘Ohe makai in Hawaiian Culture: Hawaiians fashioned ‘ohe makai branches into stilts for fun, games, and dance. These were called kukuluae‘o, after the now-endangered native long-legged black-necked stilt (Himantopus mexicanus knudsenii). Hawaiian mothers would eat ‘ohe makai fruits and then feed their baby through breast milk to cure two childhood diseases, pāʻaoʻao and ʻea. The thick resin exuded from resin ducts was also used by Hawaiians for unspecified purposes.

Collecting Seeds: On O‘ahu, look for ripe soft purple to black fruits during the spring; I normally target April for my seed collecting visits. However, I have heard reports from other Islands of ripe fruits at other times of the year, typically winter months. While it is best to collect the fruits directly from the tree, I have also been able to find dried fruits (and seeds) containing viable seeds on the ground beneath a tree. Extract the flat seeds from the fleshy fruit by hand or by using a colander. Separate the viable from nonviable seeds by placing the clean seeds in a cup of water; the viable seeds will sink. This viability test is not 100% accurate, particularly with dry seeds collected from the ground. Allow dry seeds an hour or two in the cup of water to soak up water and sink before discarding the floaters. Even then, I have had a few floating seeds germinate after deciding to sow them rather than throw them away. (I guess it just depends on how many seeds you have as to whether it is worth the materials and space to sow any floating seeds.) I nearly always sow ‘ohe makai seeds soon after collecting them. On the few occasions I have stored the seeds in my refrigerator and later (i.e., six months to several years) sown them, there was a marked reduction in germination of 50% or more compared to freshly collected seeds.

Growing from Seed: If possible, sow freshly collected seeds using Method One for the best germination. However, if you have stored seeds, rehydrate them before sowing by soaking them overnight in a shallow cup of water. Your seeds should begin sprouting in about a month. ‘Ohe makai seedlings start out with a single simple (i.e., non-compound) true leaf. As they grow, they begin producing compound leaves with three, then five, and eventually seven-plus leaflets. Seedlings also quickly develop a large fleshy root, which in the wild likely helps them survive their first few dry summers. Transfer each seedling to its own pot after it puts out 1-2 true leaves.

Seedlings grow at a moderate pace in the nursery under 50% shade, and you should have a 6-12 inch tall seedling in about nine months. Do not overwater your seedlings because this is a surefire way to kill them. A good method to avoid overwatering is to dramatically increase the drainage of your potting media by using a mix with 50% or more black cinder or perlite. Aphids and mites that disfigure the new leaves are the two most common pests to infest ‘ohe makai seedlings and young plants. Refer to Enemies in the Garden for methods of combating these foes.

Growing from Cuttings: I have never tried to grow ‘ohe makai from cuttings, and do not know of anyone who was successful.

Growth in the Garden: Most of my in-the-ground experience with ‘ohe makai is at restoration sites rather than within gardens. There, I have always planted 12-18 inch tall seedlings in sites with full sunlight since this is where I regularly see mature wild trees. As mentioned previously, because ‘ohe makai go dormant during the summer, all my plantings were during the fall or winter. (If you must plant during the summer, I recommend watering just enough to keep the soil moist, and do not expect any growth until the cooler fall months.) In the fall, my seedlings began growing rapidly, and by the following summer, I usually had a sapling 2-3 feet tall. A year after that, a sapling could be as much as six feet tall. In my experience, ‘ohe makai take five or more years of growth before they begin to flower and fruit.

In the garden, be very careful not to overwater your ‘ohe makai, particularly during the summer when it is dormant; I have seen young and mature trees die from overwatering. For the few ‘ohe makai I have grown in a garden, I watered once or twice a month during the fall, winter, and spring (but only if there was no rain and the soil was dry), and once a month during the summer. ‘Ohe makai have tender thin bark and soft semi-flexible wood. Therefore, keep all your weeding tools (e.g., power weed-trimmer) far, far away from your tree to prevent girdling, and avoid placing any weight on its branches; bird-feeders are not welcome!

Diseases & Pests: None of my older (i.e., 2-3 years) ‘ohe makai have ever died from arthropod infestations; shedding their leaves every summer may help them eliminate these pests. Rather, I have lost (and have seen others lose) ‘ohe makai because of overwatering and girdling. In one instance, I saw a full-grown tree girdled by rats (or, maybe mice). In another case, a young tree was girdled by someone getting too close with a weed-trimmer. The trunk at the soil-air interface seems to be the Achilles heel for ‘ohe makai, vulnerable to attack by microbial rot and bark-chewing pests. Therefore, inspect this area frequently on your tree, and take all appropriate actions if you see any damage.

Ā ā Ē ē Ī ī Ō ō Ū ū