BREEDING BEHAVIOR
In comparison to Anthurium where breeding studies were easy to conduct (Croat, 1980; 1983; 1986; 1991), Philodendron pollination was difficult. Cross-pollination attempts were easy in Anthurium owing to their hermaphoditic flowers and because plants often had several inflorescences per plant in different stages of development. In addition the plants reached anthesis during the day when greenhouse personnel and volunteers were available to make cross-pollinations. In Philodendron the number of inflorescences available were always fewer in number, sometimes producing only a single flower per season. In addition Philodendron collections were very seasonal in their flowering behavior (unlike Anthurium which sometimes flowered all year) making pollination all the more difficult. When flowering did occur it was often unexpected since it is difficult to tell when the spathe is ready to open. Moreover the spathe generally opens for one day only. Opening usually took place late in the afternoon after greenhouse personnel left. Even if the opening inflorescence was found in time it was generally impossible to find another plant with fresh pollen to use for purposes of experimental crosses. Philodendron pollen does not remain viable very long though it can be kept viable for a time in glassine envelopes. Ron Weeks, a grower from Homestead, Florida (pers. comm.) reports that he stores pollen in film canisters at refrigerator temperatures and that it remains viable for several weeks. He also reports that inflorescences can not be pollinated after the first evening they open. After the spathe opens (generally late in the day) it is only during the evening and night of the first night that the pistillate flowers are believed to be receptive. Attempts to pollinate plants with their own pollen have always failed if one waits until the pollen emerges. It should be noted however that Grayum (1996) reported that, based on the use of peridoxase paper which purportedly indicates the receptivity of stigmas (Young, 1986), the stigmas were receptive for up to 24 hours after anthesis. Though it seems unlikely that pistillate flowers are receptive after the first evening of anthesis, the pistillate flowers are receptive for an unknown period of time before the spathe opens so that most successful pollinations usually involved cutting a hole in the spathe after obtaining very fresh pollen from a plant in staminate phase of flowering. Though one can completely remove the spathe then protect the developing pistils with a plastic bag, it is better to simply cut a window in the spathe large enough to see most of the spathe. Then with a small brush one can spread pollen over as many of the pistils as possible, again covering the spathe for a time with a plastic bag to insure that the pollen does not dry out and fail to germinate. An effective means of spreading the pollen to insure adequate and uniform coverage is to mix the pollen with water.Failure to remove or at least loosen the bag used to cover the pollinated spadix later may result in mold developing in the spathe. Unpollinated inflorescences usually fall off within a week or two. Ron Weeks reported (pers. comm.) that for P. subg. Meconostigma in Florida the unpollinated inflorescences may persist for up to a month. Development time for fruits ranges from only a few weeks or more generally a few months and sometimes nearly a whole year. Ron Weeks (pers. comm.) reports that in P. subg. Meconostigma fruits ripen in South Florida in 2.5 to 3 months.