Based on the historical record of herbarium collections only a few species are expected to flower twice per year. This pattern may be much more common and simply masked by the year to year variation in flowering behavior. Grayum (1996) reported bimodal flowering to be common with P. subg. Pteromischum. He indicated that the two modes were quite unequal, that one of them involved far fewer individuals and lasted for a shorter period of time. Among species of P. subg. Philodendron, P. aromaticum appears to flower in the mid-dry season and mid-wet season. It is possible that the species is just too poorly known to determine. Perhaps more collections will prove it to be a typical dry-wet season flowering species. Philodendron morii may also be bimodal, with flowering collections seen in March and November, and with immature fruiting collections in December, February and June. Philodendron wilburii appears to flower at the beginning of the dry season and primarily later at the beginning of the rainy season.
The flowering behavior of P. subincisum remains doubtful because the only herbarium material was collected sterile. Although George Bunting collected a living specimen and it later flowered in the greenhouses of Cornell University, there is, to my knowledge, no date recorded as to when that event occurred. Several other species are likewise poorly know phenologically because of sparsity of flowering collections. These include P. dominicalense, P. niqueanum, and P. ubigantupense (all seen in flower only once during the early rainy season). All of these have been assumed to be species which flower entirely during the rainy season.
The phenology of fruiting is too poorly known to report on here. Most species appear to develop fruits from between 1 month to 4 months of the time of pollination, depending on the size of the infructescence but too few mature fruting collections were observed to determine the phenological period.