|My white hibiscus is now producing white&red stripped flowers (my neighbor has a red bush). I was told by an expert that cross-pollination isn't possible. Would you like a slide or two as proof? I'm amazed myself.
|I'm in agreement with the expert you consulted. Most tropical hibiscus you find in nurseries are propagated by rooting cuttings. Some varieties are easier than others to root. Hybrids are usually grafted to rootstock varieties that have proven themselves to be resistant to soil borne problems and have a strong root system. It's very likely that the red and white striped flowers you are seeing are from the rootstock rather than the grafted top of your plant. Follow one of the flowering stems down to the base of the plant to see whether it's coming from above or below the graft. I'll bet you'll find it coming directly from the rootstock.
New varieties of hibiscus can be developed from seeds. When pollen is applied to the female pads and a pod forms, it takes a few months for the pod to ripen. Getting a pod to form on a plant can be very difficult -- 60-80F degrees, high humidity and "willing" parents. After the seeds have germinated and been raised to maturity, 6 to 18 months, they will produce a flower (and bush) with qualities from both the pollen and the pod parent. Some of these flowers may be spectacular and some may be inferior to their parents. The flower produced by that seedling is genetically unique and until rooted or grafted is the only plant capable of producing that particular flower.
Hope the above information solves the mystery behavior of your hibiscus plant!