A foundation monograph of Ipomoea (Convolvulaceae) in the New World

Phenology
Many species have a distinct, relatively short flowering season. The only country where details are documented, albeit superficially is Bolivia (Wood et al. 2015). Similar details are largely unknown from other countries although information about 12 Mexican species is provided by Chemás-Jaramillo and Bullock (2005). The short flowering season is at least a partial explanation for why some species are rarely collected and so are only known from one or two examples.
Certain generalisations, however, are possible. The erect cerrado and grassland species with a stout xylopodium often come into flower soon after the start of the spring rains, possibly being stimulated into growth and flowering by the fire that often precedes the onset of rain. Annual species, in contrast, use the moist summer season for growth and come into flower towards the end of the summer, their flowers often persisting long into the winter dry season (see Chemás-Jaramillo and Bullock (2005) for examples from Mexico). Most dry forest and semi-desert species flower during the summer rainy season, taking advantage of the short wet period to produce their flowers. One subset, however, prefers to flower in the height of the dry season when they are leafless so their seeds are mature when the rains eventually begin (Ipomoea schulziana, I. juliagutierreziae). Plants of flooded pampas flower after the waters recede during the winter. There is no clear pattern amongst species of moist forest. The archetypical rain forest species, I. philomega flowers at the height of the summer but other moist forest species such as I. regnellii and I. cryptica prefer the winter.
There are many individual subtleties, which need careful observation and recording before any explanation can be provided. In Eastern Bolivia in areas of a similar altitude and climate, the first author has observed the following sequence, although these observations may be partially dependent on the date of the onset of rain. To see flowering specimens of I. hirsutissima, I. cerradoensis and I. psammophila, it is best to visit in October and November; to find I. schomburgkii, I. aprica, I. caloneura and I. paulistana it is best to look in December or January; to find I. graniticola and I. densibracteata February to early March would be best; March to early April would be good for I. amnicola, I. abutiloides and I. megapotamica; April to June would be good to find I. bonariensis, I. argentinica, I. rubens, I. bahiensis and I. cordatotriloba; to find I. ramosissima, I. setifera, I. paludicola or I. eriocalyx June or July would be best, while July or August might be best for I. regnellii, I. lactifera and I. cryptica. Finally you should note that you might find I. maurandioides in flower at almost any season.