Ipomoea cairica
(five-fingered morning glory)

Ipomoea cairica is a vigorous, perennial climber that has been widely introduced as a garden ornamental across tropical, subtropical and temperate regions. It is a fast-growing vine that spreads easily by seed and stem fragments and once naturalized, has the potential to outcompete native plants, completely invading the space by climbing and shadowing other plant species. The trailing and climbing stems of I. cairica curl around neighbouring support plants smothering native shrubs and trees, impeding their growth and preventing their regeneration. Currently, this species is listed as a weed in Thailand, Vietnam, southern USA, Central and South America and as invasive and seriously harmful to the environment in southern China, Japan, Australia, Singapore, the Canary Islands, Cuba and on many islands in the Pacific region.

The native distribution range of I. cairica is still uncertain, but it is thought to be native to tropical Africa and Asia. Currently, this species can be found naturalized across Asia, northern Africa, Australia, North, Central and South America, the Caribbean and on many islands across the Indian and the Pacific Ocean (PIER, 2018; POWO, 2020; Staples, 2020; USDA-ARS, 2020).

The risk of new introductions of I. cairica is high. This species is widely cultivated and commercialized as an ornamental. It is adapted to grow in a wide range of habitats and soil types and can be easily dispersed by seed and stem fragments (Weber, 2003; Queensland Government, 2018; ISSG, 2019; Maimela and Gumede, 2019).

Ipomoea cairica can be found growing in natural and disturbed forests, sunny meadows, sand dunes, open woodlands, coastal thickets, cliff faces, riparian forests, lake shores, swampy grasslands, stony grassy slopes, sunny mountainsides, forest edges, ruderal areas, roadsides, waste land, rubbish dumps, car yards, cultivated areas and abandoned farmlands at low to middle elevations. According to Wagner et al. (1999), I. cairica in Hawaii is a naturalized species in primarily open, dry, usually rocky, often disturbed areas, from near sea level to elevations of 670 m. Introduced in Fiji as a cultivated plant this species is now an often locally abundant weed near sea level in open places, along roadsides, on open slopes and in gardens (Smith, 1991). In New Caledonia, I. cairica is widely distributed in secondary thickets and forest edges (MacKee, 1994). It is often planted as an ornamental in gardens, fences and coastal regions (Queensland Government, 2018; Liu et al., 2016; ISSG, 2019; Maimela and Gumede, 2019; Flora of China Editorial Committee, 2020; NZPCN, 2020).

Genetics

The chromosome number reported for I. cairica is 2n = 30 (Flora of China Editorial Committee, 2020).

Reproductive Biology

Ipomoea cairica has bisexual flowers that are visited by bees [Apidae], flies [Diptera] and butterflies [Lepidoptera]. In China, carpenter bees (Xylocopa spp.) have been reported as the most effective pollinator. Controlled hand self-pollination studies by Jia et al. (2007) showed that I. cairica is self-incompatible as reflected by an absence of fruit set in the flowers, with fruits and viable seeds only being produced following cross-pollination. Fruit set failure following spontaneous self-pollination in I. cairica was also noted by Maimoni-Rodella et al. (1982).

Physiology and Phenology

Ipomoea cairica produces flowers all year round (Jia et al., 2007; Queensland Government, 2018). Wang et al. (2011) compared seed germination, growth rates and leachate phytotoxicity of I. cairica at 22, 26 and 30°C. Seed germination rates were 11.6%, 21.2% and 26.4%, respectively, while the phytotoxicity of aqueous leachates from fresh leaves varied depending on receptor plants with the strongest phytotoxic effects observed at the highest temperature (30°C).

Longevity

Ipomoea cairica is a perennial fast-growing vine. This species is adapted to grow in area with extreme seasonal fluctuations and because of its tuberous roots, it has been observed that the top part of the plant may die and later resprouts when environmental conditions are favourable (Weber, 2003; Maimela and Gumede, 2019).

Environmental Requirements

Ipomoea cairica prefers to grow in warm climates across tropical, subtropical and warmer temperate regions at elevations ranging from near sea level up to 2000 m. It may thrive in areas with full sunlight or even in light shade. It is adapted to a wide range of soil types including sandy loam, clay, salty or brackish soils and sand dunes (PIER, 2018; Queensland Government, 2018; Maimela and Gumede, 2019; Flora of China Editorial Committee, 2020).

The first occurrence of three phytophagus mites (Brevipalpus phoenicis, Tetranychus urticae and Polyphagotarsonemus latus) on the leaves of I. cairica in Parana, Brazil, was reported by Maia and Buzzi (2006).

Environmental

• Amenity

Human food and beverage

• Root crop
• Vegetable

Materials

• Fibre

Medicinal, pharmaceutical

• Traditional/folklore

Ornamental

• Christmas tree
• Cut flower
• garden plant
• Potted plant
• Propagation material
• Seed trade

Ipomoea cairica is very similar to I. purpurea, I. indica and I. hederacea [I. nil]. These species can be distinguished by the following traits (Queensland Government, 2018):

• I. cairica has hairless (glabrous) stems and 5- to 7-lobed leaves (palmately lobed). Flowers are 5-8 cm long; sepals are relatively short (4-7 mm long) and it often produces capsules containing four hairy seeds;
• I. indica has hairy (pubescent) younger stems and heart-shaped (cordate) or three-lobed leaves. Flowers are 7-10 cm long and sepals are 14-22 mm long;
• I. purpurea has hairy (pubescent) younger stems and heart-shaped (cordate) or three-lobed leaves. Flowers are 3-7 cm long; sepals are 10-15 mm long and it often produces capsules containing six hairless seeds;
• I. hederacea [I. nil] has hairy (pubescent) younger stems and heart-shaped (cordate) or three-lobed leaves. Flowers are 3-5 cm long with strongly curved sepals about 20 mm long and it often produces capsules containing four to six hairless seeds.

Due to the variable regulations around (de)registration of pesticides, your national list of registered pesticides or relevant authority should be consulted to determine which products are legally allowed for use in your country when considering chemical control. Pesticides should always be used in a lawful manner, consistent with the product's label.

Li et al. (2015) have proposed replacement control using valuable native species such as Pueraria lobata [Pueraria montana var. lobata] and Paederia scandens [Paederia foetida] as a potentially feasible and sustainable means of suppressing I. cairica.

Physical/Mechanical Control

Small infestations can be removed manually using a brush hook or similar tool. However, all roots and all stems touching the ground must be removed. For larger infestations with many stems, cutting and subsequent applications of herbicides are required (Weber, 2003; Queensland Government, 2018).

Chemical Control

Herbicides such as 2,4-D amine, dicamba and glyphosate have been recommended for the control of areas invaded by I. cairica in Australia (NSW Department of Primary Industries, 2018). Chemical control can be carried out by cutting vines at breast height, laying the lower portions on the ground and spraying them with herbicide. Regular monitoring of treated areas is necessary to control any new seedlings or regrowth (Weber, 2003; Queensland Government, 2018). Ethephon has been proposed as an alternative herbicide for the control of I. cairica (Sun et al., 2015).

03/05/2020 Original text by:

Julissa Rojas-Sandoval, Department of Botany-Smithsonian NMNH, Washington DC, USA