It is interesting to watch people when they spot a beautiful orchid flower. Whether it's a novice who enjoys a beautiful flower or an orchid connoisseur, the first thing they do is stick their nose into the flower, trying to experience its aroma.

Orchids are extremely evolved flowers that use their bright colors and patterns, interesting shapes and fragrances to perpetuate the species. Their fragrance is developed for a specific pollinator, for orchid reproduction.

In the plant kingdom, there is no other family of plants that can match the fragrance of orchids.

Orchid fragrance is a relatively volatile substance made up of oils and is produced by specialized scent glands called osmopheres. Being volatile, these oils can vaporize at specific temperatures, becoming available when the pollinator is active. The osmopheres can be found anywhere on the flower.

Approximately 75 percent of all orchids are fragrant. Some of the fragrances are undetectable to our noses, others may be very pleasing to us, and still others may be totally repulsive.

Since orchids are specific in their pollinator, the fragrance must also coincide with their activity. Most orchids are either fragrant at day or by night, but rarely both.

Evidently, producing fragrance is very strenuous activity for orchids. Brightly colored orchids, such as many of our cattleyas, tend to have sweet and spicy fragrances and are pollinated by bees. Their fragrance is normally the strongest in the morning and often barely detectable on cloudy days or at night. Other orchids, such as the bulbophyllums, are also pollinated in the day but their pollinators are flies. Needless to say, the fragrance may not be as appealing, unless you like the scent of carrion or feces.

There are many wonderfully fragrant orchids that are pollinated nocturnally. Their flower colors are normally white as it is visible at night. Sweet fragrances such as jasmine, honeysuckle, or gardenia are common and often flowers have an abundance of nectar, all of which is used to attract moths to do the pollination. Common night scented flowers are the brassavolas, aerangis and angraecums. One of the most famous orchids, Angraecum sequipedale, is a beautiful star-shaped white flower with a long 18-inch spur or nectary. In 1862, English naturalist Charles Darwin during his travels in Madagascar observed the flower and surmised that there was a moth with a proboscis long enough to reach the nectar at the end of the spur. Later, in 1903 after Darwin's death, this large moth, Xanthopan morganii praedicta, was discovered.

Orchid hybridizers have a long history of trying to perfect the shape, color, size and the blooming season of orchids, oftentimes forgetting about the importance of fragrance. Today, there seems to be a renewed interest in developing orchids specifically for their fragrance. One orchid popular in Hawai'i, oncidium Sharry Baby (registered by O'Flaherty 1983), actually smells like chocolate.

With so many combinations possible, some unbelievable scents could become available. Who knows what is in store for the future, but does anyone care what the bees think?

Scot Mitamura is an orchid horticulturist for the Honolulu botanical gardens. Reach him at hbg@honolulu.gov.