It is an unprepossessing orchid, the kind that’s unlikely to win prizes at shows or elicit a double take from passers-by. But the giant stream orchid is an irresistible enigma to some Southern California plant enthusiasts and collectors who relish a challenge.

For one, it’s elusive. You are unlikely to find it next to the common Phalaenopsis or Dendrobium at a grocery store or a garden center. Yet, if you hike into the local mountains during the spring and you look carefully, you just might spot Epipactis gigantea blooming mere steps from a stream. Look all you want, but don’t take it with you.

Also called giant helleborine, this is one of a handful of orchids that are California natives. More prolific in the wild in the northern and central parts of the state, it is less common in Southern California. Sometimes, it shows up in the strangest places, such as the occasional drainage area next to a freeway. It usually starts blooming in the late spring and early summer, then goes dormant in the fall and winter.

The giant stream orchid grows up to 1 foot, with sword-like, long leaves and inch-wide yellow/chartreuse/brown flowers with purple veins. If you shake the stalk or if a fly tries to pollinate it, the flower’s lower lip will quiver, thus earning this plant the charming moniker chatterbox orchid.

Ron Vanderhoff had been looking for the Epipactis gigantea in the wild for many years during his nature hikes in the hills and mountains of Orange County. It eluded him for a long time, making the orchid that much more alluring.

He bought his first Epipactis about five years ago from a grower, but getting the plant to look as vibrant as its wild cousins took awhile.

“I was drawn to Epipactis gigantea because they are a local native plant, but more particularly because they are an orchid, and most folks would not think of Southern California and orchids in the same context,” said Vanderhoff, a board member and Orange County native plant field trip leader for the California Native Plant Society.

“Epipactis grow only in a few areas in Orange County, so their relative rareness also attracted me,” he said. “Most serious horticulturists abhor common plants, since everyone else already has them and they are no longer special.”

During one of his hikes in the Santa Ana Mountains, Vanderhoff made his way to a spring and spotted a lush plant with flowers blooming on a nearby cliff. He could not identify it, so he photographed it. Within days, that photo somehow made its way to Harold Koopowitz, a UC Irvine professor of ecology and orchid expert who identified the mystery plant as an Epipactis gigantea.

Vanderhoff didn’t make the connection between his potted plant and the one in the wild because they bore little resemblance. Having seen the environment and moist natural conditions that the orchid thrived in, he sought to create the same for the one in his garden. It has since improved and flourished, spreading in clumps.

Roberta Fox, on the other hand, is a prolific connoisseur of orchids, with a private collection numbering between 1,800 and 1,900 that she amassed over two decades. Fox, who is co-chairwoman of the Fascination of Orchids show at South Coast Plaza Village next weekend, bought her two giant stream orchids at garden shows.

She wanted to add a California native to her extensive collection, especially a species that’s not widely available. Like other collectors, Fox is figuring out how to keep the orchid healthy and get it to bloom again next year.

“It’s one of my little projects,” Fox said. “It’s a learning process about what the plant wants and what you can give them, given the conditions and the constraints of what you have. You try to find the overlap.”

One of the essential things she found was that the giant stream orchid grows best in soil, not on bark, unlike other orchids. “Treat the orchid like a wildflower, not like an orchid,” she said.

Contact the writer: lliddane@ocregister.com