The Phragmipedium “Cardinale” orchid has its own distinctive petal shapes and colors.

Tom Mirenda is passionate about orchids. In addition to managing the plants as the Smithsonian Gardens’ orchid specialist, Mirenda keeps a personal collection of 1,000 orchids growing in his garage.

“It’s easy to fall in love with the incredible diversity” of orchids, Mirenda says, standing among the blooms of his professional labor at the “Orchids of Latin America” exhibit, presented by the Smithsonian Gardens with the U.S. Botanic Garden and National Museum of Natural History.

Orchids have become more accessible to the casual grower in recent years: You can buy an orchid at most grocery stores today. But those won’t come close to the delicacy and breeding of the orchids at this exhibition. About 300 varieties of the plant are on view in the 18th annual orchid show. (The theme changes each year, and this year’s celebrates Latin American traditions of using orchids as decor for large religious feasts.)

It must be noted that part of the reason orchids have long been considered so exotic and rarefied is their “erotic” appearance — something that’s been observed since ancient times. (Look below for some science on this matter.)

The plant family name “orchidacae” means “testicle” in Greek, and ancient Greeks believed orchids boosted virility. A Chinese legend holds that the “13 treasures” cymbidium orchid smelled so wonderful that it could help a barren woman bear that many children. And when the cattelya orchid was introduced to Europe in the 19th century, its shape “caused an absolute sensation” — especially among men, Mirenda says.

“Think about Georgia O’Keeffe and her kind of sexualized look of flowers,” Mirenda says. “Without going into too much detail, I think you could look at an orchid and see something else.

“Don’t blush!” he says, laughing. “You know what I’m talking about!”

A cymbidium “Moonwalk” orchid, left, and cymbidium heart joy “Papini” orchids are on view at the National Museum of Natural History.

1. Orchids, They’re Just Like Us!

People and orchids are “bilaterally symmetrical” — if we cut them in half in a certain way (vertically, for humans), the two sides mirror each other. (Other flowers, such as daisies, are “radially symmetrical” and can be divided on any plane.) What’s more, some orchids — such as the Miltoniopsis Princess Diana — appear to have “eyes” (symmetrical spots on the petals). In other words, “when we look at an orchid,” specialist Tom Mirenda says, “it seems to look back.”

2. Show-Offs

Orchids need to perpetuate their species, so they must attract insects and birds (which spread pollen among plants). This is often accomplished by luring those “pollinators” to the plants’ central reproductive parts. The middle “labellum” petal — tricked out with stripes, spots or extra colors — is adapted to attract pollinators.

3. Ready for Landing

“Like the lights on the runway of an airport,” in Mirenda’s words, “nectar guides” help steer pollinators toward these targets.

More Orchids in the Area

The U.S. Botanic Garden (100 Maryland Ave. SW; 202-225-8333) displays dozens of species, which you can spot in the orchid house, jungle, desert and garden court.

Hillwood Estate, Museum and Gardens (4155 Linnean Ave. NW; $5-$15; 202-686-5807) holds thousands of orchids, which are feted each March (“Orchid Month”).

The National Capital Orchid Society’s 35th annual auction (Behnke Nurseries, 11300 Baltimore Ave., Beltsville, Md.; Sat., 10 a.m.-3 p.m., free) offers a chance to view and bid on 300 to 400 species.

National Museum of Natural History, 10th Street and Constitution Avenue NW; free, through April 21; 202-633-1000. (Smithsonian)