Dombeya wallichii
(pink ball)

D. wallichii is a shrub to small tree that has been in cultivation since the 1800’s (Skema, 2010). It is only reported as an invasive species in Cuba, without further details (Oviedo-Prieto et al., 2012). Most of the information available regards D. wallichii as being cultivated, and not as a naturalised species (Skema, 2010). Although it is being listed as an invasive species in Cuba, Alvarez de Zayas (2008), reports the species as an ornamental that is rarely used in gardens in Cuba. Gilman and Watson (2014) classify the species as having little invasive potential for the USA.

D. wallichii is a shrub to a small tree in the Malvaceae family that is native to Madagascar. Skema (2014) reports that it is currently only found in a small area of eastern Madagascar with a severely fragmented distribution, and assigns it a preliminary conservation status here as Critically Endangered.

It has been reported as present, mostly as being cultivated, in Europe, North America, Central America, the Caribbean, Asia, and Oceania (See Distribution Table for details, Randall, 2007; Acevedo-Rodríguez and Strong, 2012; National Parks Board, 2016; Dave’s Garden, 2017; E-flora of India, 2017; Missouri Botanical Garden, 2017; USDA-ARS, 2017).

D. wallichii is an ornamental species being in cultivation since the 1800’s (Skema, 2010). Although it is available over the internet at some websites and nurseries, Gilman and Watson (2014) report it as not commonly available. At some of the internet sites where the species is available, it is either an expensive plant, not easy to transport, or with only few individuals in stock. Although it is an attractive cultivated species, with the little information available at present, it has a low to medium risk of introduction.

According to Skema (2010), the native distribution of D. wallichii is poorly known, as few collections had been made from wild specimens in Madagascar, mostly from the 1800’s. The habitat information from these specimens reported is: “rainforest (?)”, “sublittoral forest” and “often streamside; to 28 m”. A few recent collections are from the east coast of Madagascar. Currently the species is considered as rare in its native range: using recent, wild collections, it has an area of occurrence of just 8 km² and a severely fragmented distribution (Skema, 2014). Known wild-collected specimens come from sublittoral forest: one specimen from rainforest may not have been wild-collected (Skema, 2014).

Genetics

Chromosome numbers for Dombeya include 2n = 46, 54 and 56 (Skema, 2010).

Reproductive Biology

D. wallichii is only reported as being reproduced from stem cuttings, mainly from softwood (National Parks Board, 2016; Dave’s Garden, 2017). Bees have been observed visiting the flowers in Madagascar (Skema, 2014).

Physiology and Phenology

There is little information about the species physiology and phenology, although Skema (2014) reports from Madagascar that it flowers in July. It is reported as flowering from mid autumn into the early spring when grown as an ornamental. Its growth rate is fast (Dave’s Garden, 2017).

Environmental Requirements

D. wallichii is reported as growing in clay, sand, loam, occasionally wet; well-drained soils with an optimal pH of 6.1 to 7.8 (Gilman and Watson, 2014; Dave’s Garden, 2017). Although it has been reported as cultivated in temperate areas, it is mostly being grown in botanical gardens, as a container plant or in sheltered areas as it needs protection from frost (Billiet, 1999; Dave’s Garden, 2017; New York Botanical Garden, 2017). From the information available about its native distribution, the preferred climate zone is tropical and subtropical areas (Skema, 2010; National Parks Board, 2016). The lowest temperature zone recorded is -3.8 °C, although it is not commonly grown in temperatures that fall below 1.7 °C to 4.5 °C (Dave’s Garden, 2017). The species is drought tolerant, grows in full sun to partial shade, and will not tolerate salinity (Gilman and Watson, 2014).

D. wallichii is a species that is not commonly affected by pests and diseases (Gilman and Watson, 2014). Brevipalpus phoenicis is reported as affecting the species (Evans et al., 1993).

Environmental

• Amenity
• Wildlife habitat

General

• Botanical garden/zoo

Ornamental

• Cut flower
• Potted plant

D. wallichii can be confused with D. × cayeuxii. This species is a cross between D. wallichii and D. burgessiae, done by Cayeux in 1895 in Lisbon. D. × cayeuxii can be distinguished from D. wallichii by having narrower stipules and bracts, and the flowers being more open and lighter pink instead of darker pink Also, the staminal tube of D. wallichii is almost equal to or just surpassing the corolla in length, whereas that of D. × cayeuxii is roughly half the length of the corolla (Skema, 2010).

D. wallichii can be easily distinguished from other species in sect. Hilsenbergia by its umbellate inflorescence subtended by a conspicuous involucre of large bracts (Skema, 2014).

Although there are various sites with information about the cultivation of D. wallichii, data on its distribution, environmental requirements, biology and ecology, naturalization and invasiveness are scarce.

29/12/2017 Original text by:

Jeanine Vélez-Gavilán, University of Puerto Rico at Mayagüez