Q: My college architecture project this semester focuses on issues surrounding the landscape at Hartsfield International Airport. Part of my proposal is to create a rooftop garden that would use flowers as a way of telling time.

Do you know where I would look to find a list of the times of day at which flowers bloom? I’ve been able to find quite a bit of information of nocturnal blooming plants, but other than morning glories, I can’t find anything that specifically blooms in the morning.

A: This is a tough one! Perhaps we should start by examining the reason a plant opens a flower in the first place: to achieve pollination.

Some plants have adapted their flowering time to the presence of certain pollinators. The large white flowers of the Moon Vine in my garden open at dusk and spill their perfume across the yard. Why? Because they are pollinated by moths, which fly at night. Each morning, the flowers crumple into an unattractive sodden mass while the nasturtium blooms nearby open for business.

Later in the day my four o’clocks out by the street unfold their petals.

Flower opening occurs at predictable times under optimum conditions but morning temperature, cloudiness, rain, drought and, of course, daylength modify the daily bloom time. I like your idea to create a floral landscape at the airport but I wouldn’t want to rely on a flower clock to gauge when I should be at the departure gate.

Others have tried their hands at designing flower clocks. Visit this BBC site for lists of flowers and their expected opening times