Tacca are bizarre plants. Their nondescript appearance when not in flower enshrouds the extravagant and, dare I say macabre appearance of their blooms. The inflorescence of this genus is something to marvel at and indeed it has found at least two species of Tacca a spot in the home of many a plant collector.
Hailing from southeast Asia, these relatives of the yam must have some unique pollinators. Why else would a plant put so much energy into producing such a reproductive structure?
Many hypotheses have been put forth to explain these peculiar flowers. The most common of these is that the flowers are an example of sapromyiophily and thus mimic a rotting corpse in both smell and appearance in order to attract flies. Few studies have been done to confirm this but those who have looked into this have turned up surprising results. At least for Tacca chantrieri (the most common species horticulturally speaking) there doesn't seem to be many, if any, true pollinators.
A wide reaching study done in South Yunnan province, China found that almost nothing visited the flowers of Tacca chantrieri. Despite the presence of numerous potential pollinators, only a handful of small, stingless bees paid any attention to these quite obvious floral cues. Indeed, genetic analysis of different populations of Tacca chantrieri show that there is very little evidence of genetic transfer between populations, the opposite result of what would be expected from heavily pollinated plants.
The truth of the matter is Tacca chantrieri seems to set seed just fine without any pollination. There are a few hypotheses that attempt to explain why a species would put so much energy into producing these showy blooms that serve no benefit to reproduction. The first would be that the observations were made during times when pollinators were low.
Considering the number and variety of pollinators observed at these sites, this seems unlikely. Another could be that the flowers represent a relict condition that serves no purpose today. There could be something to this. Perhaps the genes and thus the structures involved in flowering may be too hard to evolve away from, especially if the condition has only been absent for a short period of time. Also, if the plants are reproducing just fine (especially asexually) then there may not be great reductions in fitness by continuing to produce flowers. Despite this, one would expect at least some reduction in floral production. Cost is still cost.
The point is, we simply do not know at this time. More work will need to be done to investigate these odd flowers. Until then, we can enjoy Tacca for the beautifully strange mystery they offer to us plant folk. Tacca can be maintained quite easily in the home provided they receive ample water, humidity, and good air circulation. They are also shade lovers. Given these conditions, Tacca can add a very strange accent to a dark corner of the house. I personally cannot wait until mine is old enough to flower.
Photo Credit: Hazel (http://bit.ly/1swTMn2), MaX Fulcher (http://bit.ly/1swTNY4), and Johannes Lundberg (http://bit.ly/1qB48Bw)