The only host plant species of "R. arnoldii" is "Tetrastigma leucostaphylum" in West Sumatra. "Tetrastigma" are themselves parasites of a sort, using the strength and upright growth of other surrounding plants to reach the light. The host plants of the host plants - the trees that "Tetrastigma" uses to climb up to light, are relatively limited in number of species, although they are generally the closest tree to the vine. When it is young, at least at the locations studied in West Sumatra, areas of primary forest, the vine climbs on sapling trees and bushes of "Laportea stimulans" and "Coffea canephora" in the undergrowth, in the subcanopy a "Campnosperma" species is the most important, whereas the only large tree the vine grows in is also "Laportea stimulans". "Tetrastigma" often can completely envelop its host at the subcanopy level, choking out the light to such degree that the forest floor below the canopy is completely dark -this is apparently preferred by "Rafflesia arnoldii", the most knops are found at the darkest locations in the forest. The most common plant associated with "Rafflesia arnoldii" is the smallish tree "Coffea canephora" (the well-known robusta coffee), which is actually not native to the area, but was introduced from Africa. It covers most of the undergrowth, with a Importance Value Index (IVI) of over 100%, and is also the main component of the subcanopy with an IVI of 52.74%. The dominant tall tree in these areas is "Toona sureni", which has a canopy IVI of 4.97%.