Evening primrose and buddleia, honeysuckle and jasmine: The nocturnal flowers whose scent grows headier as the sun goes down are numerous and fairly well-known. The tendency among some species to bloom at night is a response to the hardships of hot days. Both the plants and their pollinators prefer to be active in the cool of the night, so this is when they put on a show.
Almost all of the night-blooming species are to be found in warmer climates, where a drop in temperature overnight is a relief to both plants and animals. But the form of the plants varies widely. Night-blooming cereus (Cereus greggii) are spindly cactus, while moon flowers (Ipomoea alba) are annual vines that produce blooms the size of dinner plates. Ylang-ylang trees (Cananga odorata) produce blooms with such a divine fragrance that it is used in the Chanel No. 5 perfume. Epiphyllums (Epiphyllum spp.) grow like orchids or ferns high in the branches of trees in South America.
Nocturnal flowers tend to open in the late evening, then close up or drop once the sun rises. Most nocturnal plants bloom and open multiple times, but night-blooming cereus blooms only one day in June or July. It stays open all night, then the flower closes and later drops. The fragrance from nocturnal blooms tends to get stronger deeper into the night, to help pollinators find it by scent, since it's too dark for sight.
Although they bloom at night, nocturnal plants still need the proper growing conditions during the day. Many require full to partial sun in order to build up enough energy for ample, strong-smelling blooms. Plants that bloom at night take advantage of the relief from hot daytime temperatures. This is the reason that so many nocturnal bloomers require warm or hot temperatures to thrive: They have adapted to tolerate heat.
Moths and bats find nocturnal blooming flowers by scent and pale blooms that stand out in the dark. This is the reason that so many nocturnal flowers smell stronger as the evening progresses. Hummingbirds and pollinating insects that are active in the early morning or late evening may also pollinate nocturnal flowers. Night blooming flowers have fewer pollinators, but they are far more specialized toward nocturnal plants.
When growing your own nocturnal blooming garden, don't stray too far from the plant's growing conditions. Bright lights all night urge some plants to keep their blooms closed. Other plants don't produce much fragrance if night temperatures during the summer are too cold. For each species you choose, try to find a spot for it that is most like its native habitat, so that you get the most bloom and fragrance possible.