Bidens mauiensis
Asteraceae or Sunflower family [Five-minute families]
Synonymns: Bidens awaluana, Bidens mauiensis var. ciliata, Bidens mauiensis var. cuneatoides, Bidens mauiensis var. forbesiana, Bidens mauiensis var. lanaiensis, Bidens mauiensis var. media, Campylotheca mauiensis, Coreopsis mauiensis
Koʻokoʻolau
Kokolau, Kōʻokoʻolau, Koʻolau
Maui beggarticks
Natural Range & Environment
Bidens mauiensis is endemic to Lāna‘i, Maui, and Kaho‘olawe from 50 to 600 m (164 to 1,969 ft) [Wagner et al. 1990]. It is found on rocky coastal bluffs, lithified sand dunes [Wagner et al. 1990], and farther inland on dry rocky slopes.
Bidens mauiensis has the typical daisy-like flowers common to all native Hawaiian Bidens. However, reportedly, the flowers near the end of the flowering season are noticeably smaller than those at the beginning. Some wild B. mauiensis have very succulent leaves (photograph courtesy of Forest & Kim Starr CC BY 3.0 US), while cultivated plants like this one doing quite well in David's (Eickhoff) inland garden usually have thinner leaves.
Bidens mauiensis is a small prostrate species found in very rocky places (photograph courtesy of Forest & Kim Starr CC BY 3.0 US), sometimes close to the ocean (photograph courtesy of Forest & Kim Starr CC BY 2.0) and sometimes farther inland (photograph courtesy of Forest & Kim Starr CC BY 3.0 US). B. mauiensis is being used on Kaho‘olawe to revegetate areas where digging a planting hole is prohibited because of buried unexploded ordnance (photograph courtesy of Forest & Kim Starr CC BY 3.0 US).
Description
Bidens mauiensis is a small perennial herb less than 1 foot (30 cm) tall. While it's been my (Koebele) experience that cultivated plants (in pots) live two to three years, I was unable to find any data regarding the lifespan of wild plants.
The leaves of Bidens mauiensis are quite variable in both size and shape. Wagner et al. [1990] state that this variation is "genetically controlled;" however, they do not provide any evidence, reference, or research in support of this claim. In regard to shape, B. mauiensis leaves can be anywhere from simple to bipinnately compound [Wagner et al. 1990], with tripartite leaves being most common in my experience. The leaves' margins are usually toothed. Wild plants growing near the ocean often have thicker, more succulent leaves than those growing farther inland or in cultivation.
Bidens mauiensis produces solitary daisy-like flower heads 1 to 2 inches (2.5 to 5 cm) across. Wagner et al. [1990] state that the size of the heads can vary such that they are "noticeably smaller on old plants and at the end of the flowering season." The flower heads have sterile outer ray florets and perfect (bisexual) inner disk florets. This is in contrast to many other native Hawaiian Bidens species like B. amplectens, B. hawaiensis, B. menziesii, and B. torta that have inner disk florets that are either perfect (bisexual) or all pistillate (female), in which case the entire plant is female. Cultivated B. mauiensis bloom sporadically year-round; the flowering period of wild plants also appears to be sporadic but may be linked to rainfall fluctuations.
Pollinated disk florets develop into brown (when ripe), straight, and dramatically winged cypselae (a type of dry single-seeded fruit). These wings are possibly the most distinctive feature of the species (see photograph below in Special Features and Information and in the reference link) [Seeds of Hawaii] and are thought to be an adaptation to increase seed dispersal by the wind.
Growth Requirements
General
Bidens mauiensis has a number of desirable horticultural characteristics. One, it is probably the most drought-tolerant of all the native Hawaiian Bidens, making it a great choice for a xeriscape garden. Two, it can tolerate salt spray (since it often grows within a stone’s throw of the ocean), making it a good pick for a native Hawaiian coastal garden (although I don’t know how well it grows in sand). Three, it ‘likes’ to grow in very rocky areas, making it an excellent addition to a rock garden. (No one seems to know why B. mauiensis is typically seen in very rocky sites. It may be it has specific adaptations for this type of substrate, or it may be that it’s just not a very good competitor with other plants in other soil types.) Four, it is small, making it the perfect choice as a container plant.
Wild Bidens mauiensis grow in dry rocky coastal (and moderately inland) habitats, which means they have adapted to sunny, windy, and xeric conditions. Keep this in mind when placing and caring for your ko‘oko‘olau. Select a site that receives full sunlight for all or most of the day. Once established (after a few weeks), water your B. mauiensis only enough to keep the underlying soil or media moist; keep the surface soil or media dry most of the time. Make certain the soil or media surrounding the roots of your B. mauiensis easily drains away any excess water. For potted B. mauiensis, do this by making cinders a significant portion (i.e., at least 50%) of the media mix; I (Koebele) normally used mixes of about 75% black cinders. I have only used black cinders (along with some perlite) to improve the drainage of my media mixes and, therefore, cannot comment on whether or not coral rubble or sand would work equally well. Obviously, this ko‘oko‘olau is quite tolerant of salt spray.
Unfortunately, it has been my experience that cultivated Bidens mauiensis (in pots) only live two to three years. Typically, within the first year, my ko‘oko‘olau would flower for the first time and, thereafter, would flower sporadically year-round. All my potted B. mauiensis received an application of granular controlled-release fertilizer every six months, which I can only guess was helpful since I've never grown this species without fertilization.
Because cultivated ko‘oko‘olau are typically short-lived, you will need to replace them every few years if you wish to keep them long-term. The easiest way to do this is by rooting stem cuttings of your existing plant; B. mauiensis cuttings typically root easily. However, propagating ko‘oko‘olau from cuttings doesn't entirely "set back the clock" on these short-lived perennials, and these cloned plants sometimes lack the vigor of ko‘oko‘olau propagated from seeds. Also, unlike seeds, you cannot easily store a hundred ko‘oko‘olau clones in your refrigerator.
Propagating ko‘oko‘olau from seed comes with its own set of problems. The first is the unusual breeding system of many Hawaiian Bidens (see Description above). However, according to Wagner et al. [1990], Bidens mauiensis may be one of the endemic Hawaiian Bidens that only produces flower heads with perfect (bisexual) inner disk florets (i.e., no female plants), which makes collecting seeds a bit easier since you potentially only need to keep one plant in order to get viable seeds (although keeping two or more genetically different plants so they can cross-pollinate would obviously be better).
The second problem is that Bidens mauiensis can successfully hybridize with other native Bidens species [Ganders & Nagata 1984; Plants of Hawaii]. This makes collecting seeds of known genetic identity a challenge. Fortunately, a study by Knope et al. [2013] showed that B. mauiensis cannot be successfully pollinated by the introduced, naturalized, and common B. pilosa and B. alba. Unfortunately, Knope et al. [2013] did not test the other two introduced and naturalized Bidens species, B. cynapiifolia (found on all the main Hawaiian Islands except Ni‘ihau and Kaho‘olawe) and B. gardneri (currently found on Moloka‘i) [Flora of the Hawaiian Islands]. Therefore, before your ko‘oko‘olau dies, you need to decide if you are a purist and want to ensure the genetic identity of any seeds you collect or if you are okay with the possibility that the seeds you collect will have hybrid genetics (most likely native x native; much less likely alien x native). Of course, if you are only growing B. mauiensis and there are no other native or alien Bidens in your landscape or nearby — honeybees typically fly one to two miles from their hive — the chances that your B. mauiensis is producing genetically-pure seeds are more likely. However, the only way to be absolutely sure about the genetics is to bag any young flower heads you plan to collect cypselae from before they open and then pollinate them by hand. Past research [Ganders & Nagata 1984] has shown that hand-pollinating between flowers results in more viable seeds than hand-pollinating within flowers (i.e., self-pollination). Refer to Pritchardia martii for other details on how to collect genetically-certain seeds.
Pests and Diseases
Ko‘oko‘olau in general are attacked by spider mites (most common), aphids, lace bugs, mealybugs, scale insects, and spittlebugs. Snails and slugs can also sometimes become a problem. Ko‘oko‘olau are also prone to powdery mildew infections; look for white patches on the leaves. The Bidens mauiensis I (Koebele) have grown remained relatively pest- and disease-free except for spider mites. However, I have only grown this species in pots within a shadehouse. Therefore, if planted in the ground, you should keep a watchful eye for the other above-mentioned pests, particularly snails and slugs. Refer to the Pests & Diseases page for methods to control all the above-mentioned pests and diseases.
The small leaves of Bidens mauiensis make it a poor choice to grow for tea. However, if you still intend to harvest leaves, be sure you have not used any systemic or otherwise long-lasting pesticides or fungicides in the past that could potentially still be present in or on the leaves. Rather, use only short-term and less toxic chemicals like insecticidal soap and baking soda, and be sure to wash the leaves before making your tea.
Uses
Ancient Hawaiian
Nearly all the native Hawaiian Bidens species have the collective names Kokolau, Koʻokoʻolau, Kōʻokoʻolau, and Koʻolau. Therefore, it is (currently) impossible to know if all the species (about 20) were used or were used in the same way(s) by pre-contact Hawaiians. Below are the ancient uses we have found in the credible literature for plants with the names listed above.
Leaves, both fresh and dry, were used medicinally. Krauss [2001] has the most extensive account, stating that native Bidens and then later the introduced kī nehe (Bidens pilosa) were used sometimes alone and sometimes mixed with other plant ingredients to make a tea for the treatment of ʻea (thrush), constipation, asthma, tuberculosis (a post-contact disease), and as a generalized tonic.
Ka‘aiakamanu & Chun [2003] add stomach problems, "feminine illnesses," swollen neck or cheeks, and "splitting headache" to the list of treated ailments.
Modern
Today, fresh and dried koʻokoʻolau leaves are still brewed and drunk as a medicinal tonic or as an alternative to other commercially available teas. Abbott [1992] has stated, "I find that the roughly half a dozen species common in Hawaiʻi offer two or three slightly different flavors, each a bit more subtle than commercial black tea." Koʻokoʻolau tea, along with other Hawaiian teas, is sold by a few small commercial exporters, primarily using koʻokoʻolau grown on Hawai‘i Island.
If you plan to harvest leaves from your koʻokoʻolau to make tea, be sure you have not used any systemic or otherwise long-lasting pesticides or fungicides in the past that could potentially still be present in or on the leaves. Rather, use only short-term and less toxic chemicals like insecticidal soap and baking soda, and be sure to wash the leaves before making your tea.
Koʻokoʻolau flowers are occasionally used in lei [McDonald & Weissich 2003].
Special Features and Information
General
Asteraceae is a very large family of mostly herbaceous plants containing about 32,000 species within 1,900 genera with a subpolar to tropical worldwide distribution. Nearly all Asteraceae have what appears to be a single daisy-type flower that is actually a composite of several to many much smaller flowers called florets [WikipediA:Asteraceae]. There are about 250 native and non-native Asteraceae in Hawai‘i, with a little more than half being native [Flora of the Hawaiian Islands].
Many of the endemic Hawaiian Bidens species have adopted an unusual breeding strategy (see Description above) [Wagner et al. 1990]. Additionally, many have abandoned the method of seed dispersal most common among their non-native congenerics. Most non-native Bidens, like the introduced, naturalized, and now common B. pilosa (Spanish needle), have harpoon-like awns (horn-like projections) on one end of their cypselae (a type of dry single-seeded fruit) that firmly attach to bird feathers, mammal fur, and people’s socks, thereby aiding in the long-distance dispersal of their seeds [WikipediA;Bidens; Britannica]. In contrast, many native Hawaiian Bidens have no awns at all, or the awns are reduced or without the harpoon-like barbs. Instead, some ko‘oko‘olau have winged cypselae that are thought to help with dispersal by the wind. Others have corkscrew or irregularly twisted cypselae, where it's anyone's guess why they have assumed these shapes (see the photograph below). However, generally, botanists think that these alternatives to harpoon-like awns are a way for the Hawaiian species to limit, not extend, their seed dispersal [Carlquist 1980].
Pollination studies have demonstrated that native Hawaiian Bidens species will produce vigorous hybrids when crossed with other native Hawaiian Bidens species [Ganders & Nagata 1984]. Additionally, natural hybrids between Bidens mauiensis and B. menziesii and B. micrantha have been recorded [Plants of Hawaii].
A comparison of one non-native (far left) and three native Hawaiian Bidens cypselae (photograph courtesy of G.D. Carr ©).
Hawaiian Name
Bidens cosmoides is the only native Hawaiian Bidens with the species-specific Hawaiian name Po‘olā nui, while the genus is collectively referred to as Koʻokoʻolau or Koʻolau, with Kōʻokoʻolau being a variant spelling [Wagner et al. 1990; Pukui & Elbert 1986]. According to Andrews [1922], Kokolau is another name for Koʻokoʻolau. Koʻokoʻolau, Koʻolau, Kōʻokoʻolau, and Kokolau may all be compound Hawaiian words. However, because their component syllables (e.g., Koʻokoʻo, Lau) have many disparate meanings, it is impossible for us to determine an underlying meaning for the names.
Etymology
Bidens is derived from the Latin bi, meaning "two," and dens, meaning "tooth" or "teeth," referring to the two awns on the cypselae (a type of dry single-seeded fruit) [Wagner et al. 1990]. However, it's important to note that some Bidens species have no awns (e.g., Hawaiian endemics), while others, like B. pilosa, can sometimes have more than two awns [Flora of Australia].
The species name, mauiensis, refers to the island of Maui, one of the three Hawaiian islands where this species is endemically found. The suffix -ensis was added to Maui to Latinize the name [Gledhill 2008].
BPK