Flower Day

What the day is

Flower Day is observed on March 21, at the spring equinox. The practical side of arranging and caring for cut flowers sits on the Floral Design Day entry in February; this one is about what flowers are for.

Origin and background

Every visible feature of a flower is a signal directed at something that moves pollen. Color, scent, shape and timing are all tuned to a particular audience, and once you know the audience the design makes sense.

Bee-pollinated flowers tend toward blue, purple and yellow, because bees see into the ultraviolet and cannot see red as a distinct color, and many carry ultraviolet patterns invisible to us that function as landing guides pointing at the nectar. Bird-pollinated flowers, by contrast, are frequently red, tubular and unscented, because birds see red well and have a poor sense of smell. Flowers pollinated by moths and bats open at night, are usually pale or white so as to be visible in low light, and are strongly scented, since scent works in darkness where color does not.

Some are considerably less charming. Flowers pollinated by flies mimic the smell of rotting meat, and the largest of them are famous precisely for that.

The scent itself is volatile compounds released deliberately, and many flowers vary output through the day to coincide with when their pollinators fly. Cut flowers bred for shipping have frequently lost much of this, because breeding for vase life and transport durability has selected against traits including fragrance, which is why old garden roses smell stronger than florist ones.

The trade behind them is concentrated: a substantial share of the world's cut flowers passes through a single Dutch auction system.

How to take part

• Smell before you buy. Many commercial varieties have had fragrance bred out.
• Look up ultraviolet photographs of common flowers, which show the hidden patterns.
• Plant something night-scented for moths, which are underserved pollinators.
• Match plants to the pollinators you actually have locally.
• Give flowers to somebody who is not expecting them.