Bonamia menziesii – Always or recently rare?

Bonamia menziesii is rare, very rare. The US Fish & Wildlife Service (USFWS) listed B. menziesii as an endangered species in 1994 with an estimated total population of approximately 200 plants in 28 populations on five islands: Kaua‘i, O‘ahu, Lāna‘i, Maui, and Hawai‘i. In 1999 when the recovery plan was written, the total population estimate was dramatically increased to be “in the thousands” from 31 to 44 populations on the same five islands with the overwhelming majority being on Kaua‘i. However, by 2003 (the next USFWS 5-year review), the total number of plants was estimated to be less than 166 in 37 populations statewide. And, in 2013 (the last USFWS 5-year review to date), the statewide estimate was again revised downward to a total of approximately 150 plants.

Unfortunately, I have only found one reference regarding how common or rare B. menziesii was prior to 1994. This is in Flora of the Hawaiian Islands by William Hillebrand (1888), page 318, where the species is referred to as “very rare” in West Maui by Remy. (If you have any other references, please contact me so I can update this webpage.) Making my task even more difficult is the fact that there is no known Hawaiian name for B. menziesii. So, was B. menziesii a common vine in ancient times, but its name was lost like so many other things Hawaiian? Or, was B. menziesii always rare, and, therefore, Hawaiians never gave it a specific name, but simply referred to it generically as lā‘au hihi (vine)?

While my initial question, “Bonamia menziesii – Always or recently rare?”, is an interesting one, the question itself suggests, perhaps, a more important second question, “Should the recovery plan for an endangered plant that was always rare be the same as the recovery plan for an endangered plant that was once common?”

Habitat & Appearance: A critically endangered twining liana endemic to dry and mesic (and rarely wet) forests on all the main Hawaiian Islands except Ni‘ihau and Kaho‘olawe. (Bonamia menziesii is supposedly now extirpated from Moloka‘i.) B. menziesii's leathery leaves and new stem-tips are frequently but not always covered in silvery or yellowish-brown hairs. Interestingly, seedlings grown under artificial light are glabrous, suggesting it is the spectrum or heat of true sunlight that induces development of these hairs. Its bell-shaped white flowers are often inconspicuously hidden behind leaves. Fruits ripen from green to tan and look very much like those of the non-native (introduced from India) Hawaiian Baby Woodrose, Argyreia nervosa.

(Top to Bottom) Ripe fruits (capsules) and seeds. Seedling with cotyledons and true leaf. Adult Bonamia menziesii with flower.

Bonamia menziesii in Hawaiian Culture: There is no known Hawaiian name for this plant. Therefore, we do not know if B. menziesii was important or ignored by Hawaiians in pre-contact times.

Collecting Seeds: I have never seen either flowers or fruits on the few wild Bonamia menziesii I have encountered. Therefore, I do not know the best season to collect seeds from wild plants. (I do know you will need a permit from the State of Hawai‘i to legally collect seeds or cuttings from any wild B. menziesii.) The cultivated B. menziesii I have seen flower and fruit repeatedly throughout the year with no discernible pattern. Fortunately, these plants all had the ability to self-pollinate and produce viable seed – a real plus when you are dealing with such a rare species. Collect the fruits when they are dry and tan-colored. Each fruit normally holds one, sometimes two, seeds. Each seed is covered by a thin black pulp. Seeds remain viable for at least a year when refrigerated.

Growing from Seed: According to recent research (Jayasuriya et al. 2009), Bonamia menziesii seeds lacks the impermeable seed coat typical of its genus and, therefore, it is not necessary to scar B. menziesii seeds to hasten germination. After cleaning and disinfecting (i.e., 15 minutes in 10% bleach), soak the seeds 1-2 days in a shallow container of tapwater. (You do not need to remove the black pulp covering each seed during cleaning for successful germination.) Using Method One, Two or Three, B. menziesii seeds take 1-3 weeks to sprout. If you use Method One, transfer each seedling to its own pot when the cotyledons are fully developed and before the first true leaf appears (about 1 week); if you wait too long, you will have to deal with a large root mass. Seedlings grow fairly quick, producing a new leaf every 1-2 weeks. Controlled-release or dilute liquid fertilizer will hasten their growth. After 3-6 months, you should have a 1-2 foot long vine ready for planting into your garden. However, if your planting site receives full or partial sunlight, you should slowly acclimate your B. menziesii to direct sunlight in the nursery prior to planting. Otherwise, you risk burning the vine’s unadapted leaves. Sucking insects will occasionally infest seedlings. Refer to Enemies in the Garden for methods of combating these pests.

Growing from Cuttings: Propagate Bonamia menziesii from cuttings using either Method One or Two. It is also possible to root cuttings in a shaded site with daily watering. If you use this third method, remove all the leaves from the cutting and place the stem vertically in a 1:1 mix of vermiculite and perlite. It will take 1-2 months for roots to appear and another 1-2 months before there are enough roots to safely transplant your new vine into a new pot or site in your garden. I have always used a rooting hormone (e.g., Dip’nGrow®) with B. menziesii cuttings, but other native plant enthusiasts have had success without it. In my own experience, B. menziesii grown from cuttings are not as resilient as those grown from seed, perhaps because they lack a taproot.

Growth in the Garden: Bonamia menziesii grows and looks best if it has something to climb. A chainlink fence is perfect, but even a lamppost can be transformed into a beautiful leafy column. It does best in full sun but will tolerate moderate shade, and requires little to no watering after it is established. (Initially after planting, water 1-2 times a week for 1-3 months.) In a year or less, your B. menziesii should begin flowering and fruiting. If necessary, you can tame or direct your plant with modest pruning. However, remember, this vine, unlike other native vines like hunakai or pā‘ū-o-Hi‘iaka, normally has a single main stem connected to all its roots. Do not cut or damage this main stem while pruning.

Diseases & Pests: I have not observed any consequential diseases or pests on Bonamia menziesii. However, I have seen: (1) ants occasionally establish a nest at the plant’s base, (2) stinkbugs, and (3) small infestations of mealybugs or scale insects. Refer to Enemies in the Garden for methods of dealing with these pests.

Ā ā Ē ē Ī ī Ō ō Ū ū