Let’s cut right to the chase. Open air pollinated morning glories, especially the Japanese varieties, readily cross with each other and will create new combinations of traits at the drop of a hat. From the many sources on the web that I have browsed, open air pollination is used by virtually all gardeners, professional and private alike, to produce their seeds. There are various tips and tricks that I have read about, like keeping your cultivars of the same species at least a quarter mile apart to prevent crossing, but not much out there about an easy way to protect your plant from cross pollination, aside from growing it indoors away from any potential other variety. Keep in mind seeds taken from the “middle” of the plant have a better chance of being “true” compared with the seeds collected from the outer edges of the vine where insects carrying the genetic material from other cultivars are more likely to encounter the opportunity to help cross your cultivar.
Finding a crossed variety among your seeds can be very fortuitous as it provides the gardener with a brand new type of morning glory which can then be refined and sold. Think twice before removing any odd morning glories you find among your expected cultivar. It could be one in a million!
Open pollination is pollination by insects, birds, wind, or other natural mechanisms, and contrasts with cleistogamy, closed pollination, which is one of the many types of self pollination. Open pollination also contrasts with controlled pollination, a procedure used to ensure that all seeds of a crop are descended from parents with known traits, and are therefore more likely to have the desired traits.
The seeds of open-pollinated plants will produce new generations of those plants; however, because breeding is uncontrolled and the pollen (male parent) source is unknown, open pollination may result in plants that vary widely in genetic traits. Open pollination may increase biodiversity.
Some plants (such as many crops) are primarily self pollenizing and also breed true, so that even under open pollination conditions the next generation will be (almost) the same. Even among true breeding organisms, some variation due to genetic recombination or to mutation can produce a few “off types”.
One of the bigger challenges in maintaining a strain by open pollination is avoiding introduction of pollen from other strains. Based on how broadly the pollen for the plant tends to disperse, it can be controlled to varying degrees by greenhouses, tall wall enclosures, or field isolation.
Popular examples of plants produced under open pollination conditions include heirloom tomatoes.