Q: I have an island of winter jasmine that blooms every year from December through February. I wonder why it flowers in the dead of winter if the primary purpose of showy flowers is to attract insects for pollination.

A: Winter jasmine, Jasminum nudiflorum, was introduced from China in 1844. Its slender green stems and bright yellow flowers remind gardeners of forsythia. It makes an excellent cascading vine for a hillside. It never seems to overpower its neighbors. One theory holds that the flowers would be pollinated during the warmer winters of the Chinese region where it originated. Here, though, pollinating insects are absent during winter. Another theory is that most, if not all, winter jasmine plants in the U.S. are descendants of a single plant that came over in 1844 and are self-incompatible: they need pollen from a different member of the species left behind in China. You can propagate winter jasmine by burying stems and allowing them to root during summer.