On Sunday, millions of mothers will unwrap bouquets and delight at the sight of an exquisite arrangement or the monochromatic richness of a dozen red roses. But after your mom puts her Mother's Day flowers in a vase, ask her to do a little test: take a good whiff and think back to when she bought flowers for her own mother.
If her smell memory is working well, she'll recall that the flowers of yore smelled a lot stronger. It's a phenomenon that florists, flower breeders and plant biologists know well.
Decades of intensive breeding for qualities such as color and size have caused many flowers to lose much of their scent. Characteristics such as color, size, disease resistance and shelf life all were higher priorities than fragrance, said David Gang, a plant biochemist at the University of Michigan, where much of the research is going on.
"It's not like they were purposefully trying to get rid of scent," Gang said. "In our quest to get a prettier flower, we may have (reduced) its metabolic ability to have a nice scent."
By breeding only for characteristics such as color or shelf life, "you are going to give up something," said Faron Motsenbocker, flower department manager at Nature's Nook in New Berlin, Wis.
"For years, they gave up fragrance. I doubt that people notice it."
But researchers have. Efforts now are under way among flower growers and at least a couple of universities to find ways to restore stronger fragrance to flowers. Next spring, Hollandam Dutch Bulbs of America, a large importer of Holland bulbs, plans to introduce a new, more fragrant tulip, said Cor Heemskerk, president of the Wauwatosa, Wis.-based company. "It is a really sweet-smelling tulip," he said. "It's a selling point."
In the next few years, more fragrant daffodils also will hit the market, he said.
Flowers get their scent from substances known as volatile compounds - essential oils found primarily on the surface of petals. Scent actually is an aspect of flower evolution, a characteristic that might repel pests or attract desirable insects such as moths, which spread pollen.
A given flower may have dozens of volatile compounds that evaporate in warm conditions to form a distinctive scent. Roses, for example, have a large number; orchids can have more than 100 compounds. Researchers now are looking at flower genes for enzymes that form volatile compounds. That could lead to ways to manipulate genes to produce a desired scent.
Researchers at the University of Wisconsin-Madison also have gotten into the act, sending roses into space on the shuttle two years ago to see if they could develop exotic new scents that could be marketed as fragrances by the co-sponsor of the experiment, International Flavors and Fragrances of New York City. It is believed that the near-weightlessness of space can produce changes in plant oils and the chemical mix that creates scent.
The UW experiment grew flowers in a device called an "astroculture," a chamber that precisely controls growing conditions. Norman Draeger, a former UW chemist who worked on the project, said the experiment did produce a different scent, which he described as a more complex floral fragrance.
Draeger, a self-described "die-hard Rosarian," said fragrance is starting to become a priority with rose aficionados.
And although many cut roses lack scent, there are a few varieties with good fragrance. He recommended Fragrant Cloud and Tropicana, two orange rose varieties; and Mr. Lincoln and L.B. Braithwaite, both red roses.
The loss of scent has been most noticeable in old standbys such as roses and carnations. But some bulbs such as daffodils and tulips, and other flowers such as lilacs and snapdragons, also have lost scent.