Bidens menziesii subsp. filiformis & subsp. menziesii
Asteraceae or Sunflower family [Five-minute families]
Synonyms for subsp. filiformis: Bidens menziesii var. filiformis, Bidens menziesii var. leptodonta
Synonyms for subsp. menziesii: Bidens menziesii, Bidens menziesii var. lepida, Bidens salicoides, Campylotheca menziesii, Coreopsis menziesii
Koʻokoʻolau
Kokolau, Kōʻokoʻolau, Koʻolau
Mauna Loa beggarticks, Menzies' Bur-marigold
Natural Range & Environment
Bidens menziesii subsp. filiformis is found on the leeward (western) side of Hawai‘i Island and in the saddle between Maunaloa and Maunakea, Hawai‘i Island. It grows on the slopes of cinder cones and in subalpine forest from 750 to 2,200 m (2,461 to 7,218 ft) [Wagner et al. 1990]. According to NatureServe Explorer, as of 2005, this subspecies is threatened by feral ungulates and wildfires, which have burned through large portions of its habitat.
Bidens menziesii subsp. menziesii is found in leeward Moloka‘i and West Maui on dry slopes and cliffs in shrubland from 200 to 750 m (656 to 2,461 ft) [Wagner et al. 1990]. According to NatureServe Explorer, as of 2005, most of this subspecies' habitat on Moloka‘i has been severely degraded by feral goats and burned at least twice over the last two decades. Additionally, some parts of its range on West Maui have also burned.
Unfortunately, I have been unable to find any recent (i.e., post-2005) status updates, particularly in light of the Lahaina fire.
All photographs above are of subspecies filiformis. Bidens menziesii produces clusters of modest-sized flower heads (about 1 in [2.5 cm] across). The pollinated perfect and female florets develop into long, straight achenes without awns. While subsp. filiformis achenes are usually shorter and slightly wider than those of subsp. menziesii, the surest way to tell which subspecies you are looking at is to examine the leaves; subsp. filiformis leaves are hairy and (on average) about half the length of the hairless leaves of subsp. menziesii (leaf closeup photograph courtesy of Susan Fawcett CC BY-NC 4.0). B. menziesii tend to be taller in forested areas (photograph courtesy of akbirdher CC BY-NC 4.0) and more shrubby in open exposed sites (photograph courtesy of Kyhl Austin CC BY-NC 4.0). Here a cultivated B. menziesii on O‘ahu is already assuming its lanky growth form.
All photographs above are of subspecies menziesii. Bidens menziesii produces clusters of modest-sized flower heads (about 1 in [2.5 cm] across) (photograph courtesy of Forest & Kim Starr CC BY 3.0 US). The pollinated perfect and female florets develop into long, straight achenes without awns (photograph courtesy of Forest & Kim Starr CC BY 3.0 US). While subsp. menziesii achenes are usually longer and slightly thinner than those of subsp. filiformis, the surest way to tell which subspecies you are looking at is to examine the leaves; subsp. menziesii leaves are hairless and (on average) about twice the length of the hairy leaves of subsp. filiformis (leaves and flowers photograph courtesy of Kevin Faccenda CC BY 4.0). B. menziesii is often found in quite dry areas on Moloka‘i and Maui (photograph courtesy of Kyhl Austin CC BY-NC 4.0). Here a cluster of cultivated B. menziesii in a Maui garden is already assuming a lanky growth form (photograph courtesy of Forest & Kim Starr CC BY 3.0 US).
Description
Bidens menziesii is generally considered to be the tallest of the endemic Hawaiian Bidens, reportedly reaching a maximum height of about 4 m (13 ft). It is also the only Hawaiian Bidens to be classified as a shrub; the other species are all considered herbs [Wagner et al. 1990]. These tall plants typically have one to several ascending branches with the leaves and flowers clustered at the top. However, B. menziesii can also assume a shorter, more bushy form (see photographs above). Cultivated plants live a few years (if you're lucky), while the lifespan of wild plants is uncertain but likely longer.
The striking leaves of Bidens menziesii are bipinnately divided into long strap-like divisions. The living green leaves are typically clustered at the branch tips, with dead brown leaves often draping directly below and remaining on the plant for some time. Apart from their geographic range (see Natural Range & Environment above), the primary differences between the two subspecies are that subsp. filiformis has hairy leaves that are shorter (4 to 9[–12] cm; 1.6 to 3.5[–4.7] in) than the hairless longer (10 to 26 cm; 3.9 to 10.2 in) leaves of subspecies menziesii [Wagner et al. 1990].
Bidens menziesii produces multi-branched clusters of daisy-like flower heads about 1 inch (2.5 cm) in diameter. The flower heads have sterile outer ray florets and inner disk florets that are either perfect (bisexual) or all pistillate (female), in which case the entire plant is female. This breeding system is thought to maximize viable seed production in wild populations since female plants do not need to divert energy and resources to producing pollen [Ganders & Nagata 1984]. However, this dichotomy can complicate seed collection from cultivated plants (see Growth Requirements below). Wild and cultivated plants can be seen blooming year-round.
Pollinated perfect and female florets develop into black (when ripe), long, and straight achenes (single-seeded fruits) without awns. The achenes of subsp. filiformis tend to be shorter and slightly wider than those of subsp. menziesii (see photographs above and following reference links) [Seeds of Hawaii; Seeds of Hawaii].
Growth Requirements
General
The tall, lanky growth form and filamentous leaves of Bidens menziesii set it apart from most other shrubby native Hawaiian Bidens species, making it perfect as an accent in a landscape (see photographs above). It can also be kept as a container plant. However, because of its potential height (up to 4 m [13 ft]), be sure to use a heavy container to prevent it from toppling over in a windstorm.
Unfortunately, it has been my (Koebele) experience that the lifespan of cultivated Bidens menziesii is about the same as other native Hawaiian Bidens species, one to three years. Clearly, I am still doing something wrong, since I strongly suspect that wild plants live considerably longer. Based solely on their natural habitats — I haven't grown this species often enough to say for certain — subspecies menziesii may be better adapted to the warmer lowland places most of us live, while subspecies filiformis would be the preferred plant for anyone with an upland home or getaway. Regardless of the subspecies you have, try to place it in the coolest but also the sunniest place available. Also, select a location with a consistent (but not strong) breeze. Combined, these will help prevent infections of powdery mildew. While wild Bidens menziesii (both subspecies but particularly subsp. menziesii) are frequently found in relatively dry sites, it's probably best to avoid any type of water stress with your plant. In other words, always keep the soil or media surrounding the roots of your ko‘oko‘olau moist, but also make certain the soil or media drains away excess water easily. I have only grown B. menziesii in pots filled with a media mix of sphagnum peat moss, vermiculite, and black cinders or perlite (approximately one-third of each medium). However, I suspect it would grow well in more cinder-dominant media or soils.
Cultivated Bidens menziesii grow quickly and tend to assume a tall, lanky growth form. You can expect your plant to be about three feet (1 m) tall and flowering in a year or less. To prevent a containerized ko‘oko‘olau from becoming stunted, progressively transfer it to larger and larger pots as it grows. All my potted B. menziesii 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 one to three years if you wish to keep them long-term. The easiest way to do this is by rooting cuttings of your existing plant. However, propagating ko‘oko‘olau from cuttings doesn't entirely "set back the clock" on these short-lived perennials, and these cloned plants often lack the vigor of ko‘oko‘olau propagated from seeds. Also, unlike seeds, you cannot easily store away a hundred ko‘oko‘olau clones in your refrigerator.
Propagating ko‘oko‘olau from seed comes with its own set of problems. First is the unusual breeding system of many Hawaiian Bidens described above (see Description above). In order to get viable seed, you need to make sure your plant is producing perfect (bisexual) florets and not just pistillate (female) florets. This requires close examination of the flower head. Alternatively (and maybe easier), you can maintain several flowering B. menziesii at the same time, increasing the odds that at least one of the plants has perfect florets.
The second problem is that Bidens menziesii can successfully hybridize with other native Bidens species [Ganders & Nagata 1984; Plants of Hawai‘i]. This makes collecting seeds of known genetic identity a challenge. Fortunately, a study by Knope et al. [2013] showed that B. menziesii 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. menziesii 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. menziesii 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 achenes 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, 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 menziesii I (Koebele) have grown remained relatively pest- and disease-free except for spider mites and powdery mildew. Refer to the Pests & Diseases page for methods to control all the above-mentioned pests and diseases.
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.
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 with 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, including B. menziesii, 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 achenes (single-seeded fruits) 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 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 achenes that are thought to help with dispersal by the wind. Others have corkscrew or irregularly twisted achenes, 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 menziesii subsp. filiformis and B. micrantha subsp. ctenophylla have been recorded and studied near Puʻuwaʻawaʻa, Hawai‘i Island, while Bidens menziesii subsp. menziesii may occasionally hybridize with B. mauiensis and B. micrantha subsp. micrantha in West Maui [Wagner et al. 1990; Plants of Hawai‘i].
A comparison of one non-native (far left) and three native Hawaiian Bidens achenes (photograph courtesy of G.D. Carr ©).
Bidens menziesii has relatively modest flowers compared to some of the other native Hawaiian Bidens species (photograph courtesy Ganders & Lamoureux via 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 achenes (single-seeded fruits) [Wagner et al. 1990].
The species and subspecies name, menziesii, honors Archibald Menzies (1754–1842), a Scottish surgeon, botanist, and naturalist who visited and explored Hawai‘i, most notably as the naturalist on the British ship HMD Discovery, where he collected many plant and animal specimens for later classification [WikipediA;Archibald Menzies; 100 Princes Street].
The subspecies name, filiformis, is Latin for "threadlike" [Wiktionary], likely referring to the leaves of this subspecies.
BPK