Native Plants of Hawai‘i - Ipomoea tuboides

Ipomoea tuboides

Convolvulaceae or Morning glory family

Synonyms: Ipomoea tuboides f. digitata, Ipomoea tuboides f. irregularis, Ipomoea tuboides var. pubescens

No known ancient Hawaiian name

(see Hawaiian Name below)

Hawaiian moon flower, Hawaiian moonflower, Hawai‘i morning-glory

Natural Range & Environment

Ipomoea tuboides is endemic to all the main Hawaiian Islands but is thought to have been extirpated from Kaho‘olawe [Flora of the Hawaiian Islands]. It is found in mostly open, dry, rocky areas such as talus slopes and ʻaʻā lava fields, from near sea level to 610 m (2001 ft) [Wagner et al. 1990]. While occasional in a few areas, I. tuboides is rare throughout most of its range and is particularly rare on O‘ahu [Joel Lau].

While Ipomoea tuboides prefers dry, open habitats, it has a wide geographic and elevational range from Lāna‘i coastlines (photograph courtesy of Forest & Kim Starr CC BY 2.0) to inland East Maui lava fields (photograph courtesy of Forest & Kim Starr CC BY 3.0 US) to far up in the dry southern Wai‘anae Mountain Range of O‘ahu (photograph courtesy of Joel Lau ©). Header photograph courtesy of Forest & Kim Starr CC BY 3.0 US.

Just when you think Ipomoea tuboides always has heart-shaped leaves (photograph courtesy of Forest & Kim Starr CC BY 3.0), you can come across an I. tuboides with leaves like this (lobed-leafed I. tuboides photograph courtesy of Forest & Kim Starr CC BY 3.0 US). These I. tuboides seedlings, emerging after the rains, are part of the effort to restore Kaho‘olawe (photograph courtesy of Forest & Kim Starr CC BY 3.0 US).

Description

Ipomoea tuboides is a climbing vine (without tendrils), often growing in places with nothing to climb on (see photographs above), that is typically herbaceous but may become somewhat woody near its base on older plants. Stems are hairless or nearly so and sometimes brownish red with small green pimples. While a perennial, the lifespan of wild plants seems to be variable, with some plants living for many years (but often seasonally dying back), while others disappear after one to a few years. Cultivated plants have a similar variable lifespan depending upon the environmental conditions of the planting site and the amount of pest management.

Ipomoea tuboides has heart-shaped, egg-shaped, or lobed leaves up to 15 cm (6 in) long [Wagner et al. 1990]. The leaf surfaces are dull and hairless, and the leaf margins are typically entire but occasionally toothed.

Ipomoea tuboides nearly always produces solitary, perfect (bisexual) flowers, each on a very long peduncle. The flower's sepals, an important feature in identifying this species, are pointed and lie close to the corolla but curve back as the fruit develops. The corolla is long and trumpet-like, having a very thin tube (less than 5 mm in diameter) with its petals flaring out abruptly at the end. Flowers open in the evening and close the following morning, often with a lavender tint as they wilt but eventually turning tan. Flowering is sporadic. Pollinated flowers develop into small (less than 1 inch [2.5 cm] in diameter), ovoid fruits that ripen into dry, smooth, brown capsules that typically split open to reveal one to four small, dark brown, bristly, ovoid seeds [Seeds of Hawaii].

There are more than a dozen native and non-native species of Ipomoea in Hawai‘i. Unfortunately, there are two species that look much like our endemic Ipomoea tuboides: the non-native and naturalized (or possibly indigenous) Moon flower (Ipomoea alba) and the non-native and naturalized Beach moonflower (Ipomoea violacea). The most reliable way to identify the three species is to look closely at their flowers, particularly the sepals. Ipomoea tuboides has pointed sepals, but not the dagger-like points you see in I. alba. Meanwhile, I. violacea has non-pointed (rounded) sepals. Additionally, the corolla tube of I. tuboides is less than 5 mm in diameter, while the diameter of the corolla tube of the other two species is 5 mm or greater. Some other differences are (1) Ipomoea tuboides flowers fade to lavender, while the other two typically do not fade or fade to yellowish-brown; (2) Ipomoea tuboides has hairy seeds, while the other two species have hairless seeds; (3) the sap of Ipomoea tuboides is usually clear or nearly so, while the sap of the other two species is typically milky.

The most reliable way to distinguish our endemic Ipomoea tuboides from the non-native I. alba and I. violacea is to look closely at their flowers, particularly the sepals. Ipomoea tuboides has pointed sepals (photograph courtesy of Kevin Faccenda CC BY 4.0), but not the dagger-like points you see in I. alba (photograph courtesy of Forest & Kim Starr CC BY 2.0). Meanwhile, I. violacea has non-pointed (rounded) sepals (photograph courtesy of jmull28 CC BY-NC 4.0). Additionally, the corolla tube of I. tuboides is less than 5 mm in diameter, while the diameter of the corolla tube of the other two species is 5 mm or greater.

Growth Requirements

General

The growth behavior and requirements of Ipomoea tuboides are much like those of its sister species, koali ʻawa (I. indica). In the wild, it tends to grow rapidly, flower profusely, then decline and die back (sometimes disappearing completely), only to later reappear and repeat this cycle. Landscape location and time invested in pest management seem to largely determine the length of a similar cycle for cultivated plants, with plants grown in dry, sunny sites that are regularly monitored and treated for pests persisting longer before they eventually die back or die altogether. Because of this impermanence, I. tuboides is best used as a temporary (but often repeating) feature in a landscape rather than something more permanent such as a groundcover. Also, because I. tuboides is a climbing vine that can grow rapidly and smother nearby plants, avoid planting it close to other plants unless you are willing to regularly prune it. Similarly, as a container plant, its long vines need to be regularly pruned.

Ipomoea tuboides does best in a site with full sunlight for all or most of the day. Once established in the ground (after a few weeks), it's unlikely you'll need to water your plant at all unless it displays obvious signs of drought stress (e.g., wilted leaves). However, if you do see wilted leaves, before watering, inspect your plant for an alternative cause — the sweetpotato weevil. Obviously, a containerized plant will require regular watering.

Ipomoea tuboides can tolerate extreme heat, drought, strong winds, and some salt spray. It doesn't seem to be fussy about soil or media and will grow in sandy, calcareous, clay, cinder/lava, and organic-dominant types, provided the soil or media drains water readily. Avoid fertilizing in-the-ground plants since this is likely to make them more attractive to pests. If your potted I. tuboides fails to grow, you can try applying a balanced controlled-release fertilizer every six months or a foliar fertilizer at ⅓ to ¼ the recommended strength every few months.

Perhaps the biggest difference between Ipomoea tuboides and other native Hawaiian Ipomoea is that it opens its flowers near sunset and closes them near sunrise; all the other native Hawaiian Ipomoea are day-bloomers. (However, some taxonomists think that Ipomoea alba, also a night-bloomer, may be a native species [Plants of Hawai‘i].) Therefore, I. tuboides is, perhaps, most attractive to those plant lovers who enjoy sitting and relaxing on their lanai at the end of the day. Another difference is that, unlike some native Ipomoea like koali ʻawa, I. tuboides regularly sets seed. Therefore, be sure to collect and store these seeds (in the refrigerator) before your plant dies unexpectedly.

Pests and Diseases

Ipomoea tuboides is vulnerable to many of the same pests that attack other Ipomoea in Hawai‘i, such as ‘uala (sweet potato; Ipomoea batatas), hunakai (Ipomoea imperati), koali ʻawa (Ipomoea indica), and pōhuehue (Ipomoea pes-caprae subsp. brasiliensis). Most damaging among them is the sweetpotato weevil (Cylas formicarius). Other pests include the sweet potato bug (Physomerus grossipes), flea beetles, and spider mites. If your landscape is home to or visited by snails and slugs, these can also become a problem. These pests are usually less common and their damage less severe for plants growing in sunny, dry sites and/or near the ocean. Refer to the Pests and Diseases section of Ipomoea imperati and Ipomoea pes-caprae subsp. brasiliensis as well as the Pests & Diseases page for more information and ways to battle these pests.

Uses

Ancient Hawaiian

There is currently no known (i.e., documented) Hawaiian name for Ipomoea tuboides, and, therefore, no recorded ancient uses. However, if Hawaiians recognized I. tuboides as a koali (some kinds of morning-glory [Ipomoea spp.] [Pukui & Elbert 1986]), they may have used it in ways similar to other native Ipomoea species such as hunakai (I. imperati), koali ʻawa (I. indica), and pōhuehue (I. pes-caprae subsp. brasiliensis).

Modern

Special Features and Information

General

Convolvulaceae contains more than 1,650 species within about 60 genera distributed worldwide in both tropical and temperate regions. Most are herbaceous vines or herbs, but the family also includes some trees and shrubs [WikipediA; Convolvulaceae, Britannica; Convolvulaceae].

In addition to Ipomoea tuboides, native Hawaiian members of Convolvulaceae include the endemic and endangered Bonamia menziesii; the indigenous makihi (Cressa truxillensis); the endemic and parasitic kaunaʻoa (Cuscuta sandwichiana); the indigenous hunakai (I. imperati), koali ‘awa (I. indica), White-flowered beach morning glory (I. littoralis), and pōhuehue (I. pes-caprae subsp. brasiliensis); and the endemic pāʻu-o-hiʻiaka (Jacquemontia sandwicensis) [Flora of the Hawaiian Islands]. I. tuboides is also related to the non-native and locally popular food plants ʻuala, or sweet potato (Ipomoea batatas), and ung-choi, or swamp cabbage (I. aquatica).

Ipomoea tuboides is the only endemic species of Ipomoea in Hawai‘i.

Hawaiian Name

Given the wide geographical range of Ipomoea tuboides within Hawai‘i and its distinctive night-blooming flowers, it's hard to believe that pre-contact Hawaiians did not assign a name to this endemic vine. Unfortunately, like far too many of our native plants, that Hawaiian name is currently unknown.

Etymology

Ipomoea is derived from the Greek words, ips, for "worm," and homoios, meaning "similar to," referring to the species' twining habit [Wagner et al. 1990]. The species name, tuboides, comes from the Latin word tuba, meaning a "long trumpet" [Wiktionary], and the ancient Greek suffix -oides, meaning "-like," "-resembling" or "-shaped" [Gledhill 2008], obviously referring to the long and tubular flower of this species.

BPK