Selections of different geraniums are bound together in Robin Parer's Kentfield, Calif., home. True geraniums are often confused with pelargoniums because they were classified in the same genus in the mid 1700s. Geraniums are small and compact, and their blue, pink or white flowers have a delicate look.

WALNUT CREEK, Calif. — You know that beautiful pot of geraniums with the gorgeous red blooms you have growing alongside your deck? We hate to tell you this, but those aren't geraniums.

Neither are the ones on the hillside with the vivid orange flowers. And the pot of lemon-scented geraniums hanging by the front door? Sorry, but no.

You can blame the father of plant taxonomy, Carl Linnaeus, who decided there was no reason to divide the geraniums from the pelargoniums, the plants you most likely do have.

Robin Parer, a leading expert on geraniums and pelargoniums who owns a Marin County, Calif., nursery that specializes only in geraniums, pelargoniums and the related erodiums, is on a bit of a one-woman mission to correct an historical mistake that has people falling in love with a wrongly named plant while missing out on some truly amazing correctly named plants.

"Geraniums are fantastic plants," Parer said. "They are really like wildflowers that we've captured and brought into the garden."

Geraniums are enduring plants with a huge number of varieties available for almost any condition. They differ from pelargoniums in a number of ways. The most distinct, however are size and color of blooms. Geraniums are small and compact, and their flowers have a more delicate look to them. The flowers are blue, pink or white. If you've got a geranium with red flowers, you've actually got a pelargonium.

The problem started more than 300 years ago with properly identified geraniums growing happily in England. Then the British got a bit of wanderlust and started exploring the globe. During ocean voyages, British ships would stop at the Cape of Good Hope to resupply their ships, and the crew would do some exploring, collecting samples of the flora they found.One of the plants they found was Pelargonium triste, a South African native that bore an unfortunate resemblance to the geranium.

In the mid 1700s, Linnaeus, a Swedish botanist and doctor, began studying the taxonomy of plants and created an ordering system. Because the geranium and pelargonium are both members of the Geraniaceae family, Linnaeus, over the protests of some botanists, included both in the same genus, Geranium.A few decades later, botanist Charles L'Heritier set the record straight, but the average gardener hasn't been much bothered by the distinction.

Parer, an Australian who followed her heart to the United States, has long been fascinated by true geraniums and some varieties of pelargoniums. She opened her nursery, Geraniaceae, 23 years ago, growing a staggering number of geraniums at her one-acre multiterraced home garden. Her assortment of scented and unusual pelargoniums are grown in a 10,000-square-foot rented commercial greenhouse in Richmond, Calif.Parer's interest in geraniums began when she first came to California 35 years ago. She saw "great festoons" of pelargoniums growing seemingly everywhere she looked. While beautiful, they gave Parer pause."I didn't want to grow them," Parer said. "They were monsters that would take over the garden."Instead, she met a Cambridge taxonomist who taught her about geraniums and even supplied some seed she used to start her nursery. She now has more than 500 species of geraniums, about 150 scented pelargoniums and a large variety of angel and pansy-faced pelargoniums. She produces her catalog of plants each year.

Geraniums are a plant for the ages, perhaps now more than ever. With the move toward downsizing homes and gardens, the smaller, more compact geranium is a great fit for the smaller garden.Parer has a fondness for the identity thieving pelargoniums, too, although you won't find any zonals or Martha Washingtons in her garden or her stock.Her preference is for the unusual varieties that produce bottlebrush blooms, release their aroma only at night, or have black petals. Those are for those who, like Parer, have unusual gardening tastes. More popular are the scented leaf varieties that come in almost every scent imaginable.

So, is there a simple way of knowing whether that prized plant is a geranium or pelargonium? Yes, Parer said. In addition to the size and color differences, geraniums tend to die back during the winter and return in the spring. Pelargoniums can grow to the size of shrubs and in a Mediterranean climate, can flower almost year round.It would be nice if the world recognized the difference between the two. But it doesn't matter what you call them, Parer said, as long as you plant them, love them and enjoy them.