DESCRIPTIONS OF D. bulbifera, A. elliptica and A. crenata

Dioscorea bulbifera (air potato, bitter yam)

Ecology and growth form : The presence of this species in Florida was first recorded by Henry Nehrling in 1905 but the introduction of this species to North America can most likely be attributed to slave ships from Africa (Coursey 1967). Today, D. bulbifera ranks as either the 4th or 5th crop yam in the world (Martin 1974). This species is believed to have originated in Asia but is found all over the tropics. Dioscorea bulbifera has been cultivated in home gardens as a food source for such an extensive period that wide diversity has been observed in species morphology (Coursey 1967, Martin 1974) throughout the Old World. Despite being noted in the floras of Central and South America, this species is not an important food source within the New World (Martin 1974).
In describing this species, Martin (1974) observed that the underground tubers were sometimes attacked by beetles and nematodes but they appeared to be more resistant than tubers of other species.

Impact on Florida vegetation:Dioscorea bulbifera reproduces vigorously asexually (via aerial bulbils) in Florida. The plant forms a thick blanketing vine and can shade out both canopy and understory vegetation. After Hurricane Andrew, D. bulbifera was one of the dominant components of the hammock community canopy. At present, removal of this species is limited to repeated physical and chemical removal, with no long-term alternatives to species control.

Ardisia elliptica (shoebutton ardisia) and A. crenata (coral berry, coral ardisia)
Ecology and growth form: Ardisia elliptica was introduced into Florida as an ornamental in 1900 (Gordon and Thomas 1997). Having escaped cultivation, this species can now be found in most South Florida counties (Wunderlin and Hansen 2004) where it often displaces native understory species by forming dense monospecific stands (Koop 2003). Fruits of these species are eaten by locals in Peninsular Malaysia and defined as tasting similar to Eugenia jambolana (Martin 1974).
Ardisia crenata was introduced into Florida about the same time as A. elliptica. This species is now recorded in 14 northern Florida counties as well as in Texas (Singhurst et al. 1997). Like A. elliptica, this species is shade-tolerant and can form monospecific carpets that displace native communities (Langeland and Burks 1998). Burkill (1935) reports that seeds of A. crenata are eaten by the Malays while the indigenous people of the Peninsular and the Javanese use the leaves as a salad. Leaf and root juices are also used to treat among other ailments, fevers, coughs, diarrhea and ear-ache.

Impact on Florida vegetation: These plants represent a significant threat to the remaining closed-canopy natural areas in Florida as they shade and outcompete native understory species, altering forest structure and function (Gordon 1998, Horvitz et al. 1998). These invasive also have the capacity to displace native species such as A. escallanoides (marlberry) and the endangered Argythamnia blodgettii (Blodgett's silverbush).
Dense growth of D. bulbifera on a fence in Orlando (FL, USA). This vine has almost completely shaded out the grapevine that originally grew on the fence.
A D. bulbifera growing up a fruit tree in a home garden in Kulim (Penang, Malaysia).

Ardisia elliptica growing in deep shade in the remote Everglades saline ecotone (Florida, USA).

Ardisia elliptica trees forming a living fence at the Forest Research Institute (Selangor, Malaysia).