"Trillium grandiflorum" has long been thought to self-pollinate based on the fact that pollinators had rarely been observed visiting the plants and because there is low variation in chromosomal banding patterns. This has been strongly challenged, as other studies have shown high pollination rates by bumblebees and very low success of self-pollination in controlled experiments, implying that they are in fact self-incompatible. Several ovules of a given individual often fail to produce seeds. One contributing factor is pollen limitation, and one study showed that open pollinated plants had 56% of their ovules produce seeds, while in hand pollinated individuals the figure was 66%. Plants with reduced exposure to pollinators were 33% to 50% less likely to produce fruits than those that were, while hand pollinated individuals showed a 100% fruit set (though these fruits did not contain a 100% seed set). Plant resources were shown to be a limiting factor in seed production: when pollen was in abundance, larger plants had a significantly greater seed to ovule ratio than smaller ones. The overall suboptimal seed to ovule ratios suggest that "Trillium grandiflorum" has evolved to maximize reproductive success in the face of highly stochastic pollination, where some plants may only be visited by a single pollinator in a season.