Native Plants of Hawai‘i - Viola chamissoniana

Viola chamissoniana subsp. chamissoniana, subsp. robusta & subsp. tracheliifolia

Violaceae or Violet family

Synonyms for subsp. chamissoniana: Viola chamissoniana, Viola helioscopia

Synonyms for subsp. robusta: Viola robusta

Synonyms for subsp. tracheliifolia: Viola chamissoniana var. olokelensis, Viola chamissoniana var. tracheliifolia, Viola robusta var. mauiensis, Viola tracheliifolia, Viola tracheliifolia f. canescens, Viola tracheliifolia f. mauiensis, Viola tracheliifolia f. olokelensis, Viola tracheliifolia var. olokelensis, Viola tracheliifolia f. populifolia, Viola tracheliifolia var. populifolia, Viola tracheliifolia f. puberula, Viola tracheliifolia f. tomentosa, Viola tracheliifolia var. tomentosa

‘Olopū

Pāmakani

Natural Range & Environment

The three subspecies of Viola chamissoniana have differing geographic ranges and primary habitats. The extremely rare and endangered subsp. chamissoniana is endemic to the Wai‘anae Mountain Range on O‘ahu, where it is found growing on dry cliffs, rocky ledges, and steep slopes in mesic areas [ECOS]. Subspecies robusta is more common but is also endemic to only one island, Moloka‘i, where it grows in wet forests. The most common and widespread subspecies is subsp. tracheliifolia, which is endemic to Kaua‘i, O‘ahu, Moloka‘i, and Maui, where it grows in mesic forests [Wagner et al. 1990]. Unfortunately, it seems only Wagner et al. [1990] and the US Fish & Wildlife Service [ECOS] provide elevational ranges for the species as a whole (330 to 1,890 m [1,083 to 6,201 ft]) and subsp. chamissoniana in particular (414 to 1,149 m [1,358 to 3,770 ft]), respectively.

Subspecies chamissoniana was federally listed as endangered in 1991. At that time, there were only 14 documented wild plants. Subsequent surveys revealed a much larger population of 300 to 700 wild plants; in the latest USFWS 5-Year Review [2024] there were an estimated 293 mature and 60 immature wild plants at four population units and an unknown number at four additional population units. The Army Natural Resources Program on O‘ahu (ANRPO) has been responsible for the bulk of the management of subsp. chamissoniana with fencing to exclude ungulates, invasive nonnative plant and rat control, seed collection and storage, and maintaining a living plant collection. They have also been active in planting propagated plants into some of their management areas [USFWS 2019; USFWS 2024].

Unfortunately, the flower of this cultivated ‘olopū (Viola chamissoniana subsp. chamissoniana) is not nearly as large as it appears in this close-up photograph; other photographs above and below give a more accurate visualization of flower size. Each pollinated ‘olopū flower develops into a capsule (subsp. robusta photograph courtesy of NPS-pacific island vegetation monitoring CC BY-NC 4.0) that will ripen, dry, and explosively split open to reveal its tiny, enclosed seeds (subsp. tracheliifolia photograph courtesy of Forest & Kim Starr CC BY 3.0 US). Decumbent ‘olopū stems will sometimes root in moist habitats (subsp. robusta photograph courtesy of Gerry Carr CC BY-NC 4.0). Header photograph of subsp. tracheliifolia courtesy of Gerry Carr CC BY-NC 4.0.

Despite the size, shape, and color differences between the leaves of these three plants, all are considered to be within the subspecies tracheliifolia (photograph of large, dark leaf courtesy of Chris Havran CC BY-NC 4.0; photograph of pale, all-green leaf courtesy of Kenneth R. Wood (NTBG) CC BY-NC 4.0; photograph of small, oval leaf courtesy of Forest & Kim Starr CC BY 3.0 US).

Description

Viola chamissoniana is a shrub with some plants having numerous branches while others have a single branch. The US Fish & Wildlife Service [2024] considers V. chamissoniana (subsp. chamissoniana) to be a short-lived (less than ten years) perennial. However, this seems to be a subjective assessment since I (Koebele) was unable to find any formal studies regarding lifespan, and the species (to date) is rarely cultivated. What is distinctive about V. chamissoniana and some of the other endemic Hawaiian Viola is that they are woody shrubs, sometimes becoming quite tall (e.g., subsp. chamissoniana reportedly gets to be up to 90 cm [3 ft] tall [ECOS]), unlike Viola species outside Hawai‘i, which are primarily herbaceous [WikipediA; Viola (plant)].

If there were only two subspecies of Viola chamissoniana, subsp. chamissoniana and subsp. robusta, determining what subspecies you were looking at would be fairly easy since they are separated geographically (subsp. chamissoniana is endemic to O‘ahu, while subsp. robusta is endemic to Moloka‘i) and by habitat (subsp. chamissoniana grows on dry cliffs, rocky ledges, and steep slopes in mesic areas, while subsp. robusta grows in shaded, wet forests). Distinguishing between the two morphologically is more difficult. According to Wagner et al. [1990], subsp. chamissoniana typically has smaller leaves with a shorter petiole (leaf stalk) than subsp. robusta and rarely has more than one flower per peduncle (flower stalk) compared to subsp. robusta, which usually has more than one flower per peduncle. However, after looking at the plants I have grown and conducting an online photo-survey, I (Koebele) am not sure these differences are real since I see a lot of overlap.

What really makes subspecies identification difficult is the third subspecies, subsp. tracheliifolia, which is highly variable morphologically, much more common than the other two subspecies, and overlaps the two other subspecies geographically. In identifying subsp. tracheliifolia, the most reliable features are habitat (shaded mesic forest) and its larger leaves (up to 29 cm [11 in] long) with a long petiole (up to 8 cm [3 in] [Wagner et al. 1990]. However, because these features also overlap with the other two subspecies, in reality, most of us will need to consult a professional taxonomist whenever we encounter an ‘olopū.

The small, bilaterally symmetric, 5-petaled, perfect (bisexual) flowers of Viola chamissoniana also vary, primarily in color, but not in a way that obviously correlates with subspecies. Flowers are predominantly white but with varying amounts of purple streaking or tinge. Pollinated flowers develop into sausage-shaped capsules. When ripe, the capsules become dry and explosively open along a three-way split to reveal and (at least partially) disperse the many tiny, dark brown to black, egg-shaped seeds inside [see photograph above].

Growth Requirements

General

According to everything I (Koebele) have read and everyone I've talked to, our native Hawaiian Viola are eagerly devoured by the introduced giant African land snail (Lissachatina fulica) and other introduced terrestrial gastropods. Therefore, my ‘olopū cultivation experiences are limited. I have never planted an ‘olopū in a landscape. I also have never grown subspecies robusta and only briefly kept subspecies tracheliifolia in a nursery before the lone plant died because of an irrigation failure. Therefore, nearly all my statements and advice below are based on my experiences growing subspecies chamissoniana indoors under LED lamps, a very protected and controlled environment.

‘Olopū do well under LED lamps, growing at a pace that matches their pot size and media mix. For example, in the photograph to the right are three ‘olopū of identical age and parentage (i.e., from the same seed batch). The smallest in the foreground is growing in the smallest pot, a bonsai training pot, filled with 100% black cinders. The next slightly larger ‘olopū (background right) is growing in a slightly deeper 4-inch (10 cm) pot filled with 100% black cinders. Lastly, the largest plant (background left) is also growing in a 4-inch pot. However, this pot is filled with a media mix of 90% black cinders and 10% sphagnum peat moss.

Despite their size differences, all three plants began flowering at the same age of about nine months. However, while the two smaller plants only sporadically produce flowers, the larger plant produces multiple flowers almost continuously.

These three plants, and others I have previously grown in an equal media mix of sphagnum peat moss, vermiculite, and perlite, all receive fertilizer on a regular basis; once a month, I apply one dose of organic (i.e., seaweed flakes) fertilizer, and every time I water (every other day) I use a "feeds-every-time-you-water" (10-15-10) liquid fertilizer at half the recommended strength. Since I've never grown ‘olopū without fertilizer for an extended period, I cannot say the fertilizer is essential for good growth.

‘Olopū begin flowering when they are quite young — less than a year old — seemingly independent of their size. To date (2026), I've been unsuccessful at getting any of my ‘olopū to produce seeds after hand-pollinating the flowers, and I am beginning to suspect they need to be cross-pollinated. It is also interesting that my ‘olopū begin producing basal shoots after reaching about 6 inches (15 cm) in height, while none of my plants have ever produced a side branch coming from the main branch.

Pests and Diseases

Undoubtedly because I have grown all my ‘olopū indoors, I have had almost no pest or disease problems save one. Something — I suspect mites — regularly causes the newest leaves to emerge contorted. When this starts to happen, I carefully remove the distorted immature leaf and spray all the plant's growing tips with horticultural oil, which temporarily remedies the problem. Therefore, as a prophylactic, you may want to spray your ‘olopū with horticultural oil or a miticide on a regular schedule to avoid this headache. Refer to the Pests & Diseases page for other ways to combat mites.

Uses

Ancient Hawaiian

I (Koebele) was unable to find any ancient Hawaiian uses for this species.

Modern

Special Features and Information

General

Violaceae, the true violets and pansies (African violets are not true violets and are in the family Gesneriaceae), are herbs, shrubs, lianas, and small trees with about 1,000 species in 25 genera. They are found mostly in tropical and subtropical areas except for numerous Northern Hemisphere temperate species of Viola. Most species in the largest genus, Viola, are herbs [WikipediA; Violaceae]. However, some of the endemic Hawaiian Viola are a rare exception and become woody shrubs. Violets are popular garden ornamentals but also have a long history of culinary and (traditional) medicinal uses [Batiha et al. 2023].

In addition to Viola chamissoniana, other native Hawaiian members of Violaceae include six additional endemic Viola species and four endemic species of aupaka (Isodendrion spp.) [Flora of the Hawaiian Islands].

Many Viola species have a dual reproductive strategy with both chasmogamous flowers that are above ground, open, and typically cross-pollinated by insects or other vectors and cleistogamous flowers that are normally near or below ground, closed, and self-pollinated [Awkward Botany]. Currently, all the endemic Hawaiian Viola are thought to be strictly chasmogamous, with only V. kauaensis having cleistogamous flowers [Havran et al. 2014].

Viola chamissoniana subsp. robusta hybridizes with V. maviensis along the margins of Pēpē‘ōpae Bog, Moloka‘i [Wagner et al. 1990].

Hawaiian Name

In addition to being the Hawaiian name for Viola chamissoniana, ʻOlopū can also mean (1) an adze for cutting ʻōhiʻa logs for images and (2) "inflated, billowed out, as a sail in the wind; puffed out, as cheeks of one eating; blistered, as hands from work; mouthful of food or water. hō,ʻolo.pū To dilate, inflate, blister" [Pukui & Elbert 1986].

The name Pāmakani is sometimes also used for the endemic hibiscus, kokiʻo keʻokeʻo (Hibiscus arnottianus) [Pukui & Elbert 1986], as well as at least one species of endemic Hawaiian Tetramolopium, T. capillare [Wagner et al. 1990].

Etymology

Viola is the Latin name applied to several fragrant plants and is equivalent to the Greek name ion [Gledhill 2008]. The species and subspecies name, chamissoniana, honors Adelbert von Chamisso (1781–1838), a French-born German explorer, naturalist, writer, poet, and plant collector [WikipediA; Adelbert von Chamisso]. The subspecies name, robusta, is Latin, meaning "mature, strong, hard, solid, hardy, durable, of oak, and valiant" [Latdict]. The subspecies name, tracheliifolia, is derived from the Latin trachelium (from the Greek trachelos), meaning "neck" and folium, meaning "leaved" [Gledhill 2008].

BPK