FOREST OF CHOICES: Shimeji, left, king trumpets, center, hen of the woods, back right, are making their way to major markets. (Mark Boster / Los Angeles Times)

KING trumpets that have a texture almost as firm and meaty as young porcini; shimejishimeji that have a flavor that is wonderfully nutty; hen of the woods with a taste as earthy as their name. If you still think the cutting edge in grocery store mushrooms is enoki, shiitake and portobello, you've got some very pleasant surprises coming.

And if one Southern California partnership has its way, there are going to be plenty of those surprises available too.

In San Marcos, just north of San Diego, the Japanese mushroom giant Hokto Corp. is working with its American partner, Golden Gourmet Mushrooms, to build a massive, Space Age growing facility that within just a couple of years will be producing as many as 6 million pounds of these exotic mushrooms annually.

That's more than triple the amount of king trumpets, shimeji and hen of the woods sold in the United States last year. And though, according to the USDA, they represent less than 1% of all fresh mushroom sales (more than 675 million pounds last year), they're part of a segment that is increasingly profitable.

Though sales of the common button-type mushrooms have been mostly flat for the last five years, specialty mushroom sales increased 9% last year in spite of an average cost that's more than double the cost of buttons. "In the big picture, we're a fly on an elephant's behind," says Golden Gourmet President and Chief Executive Craig Anderson. "But it's been the biggest growth area in the industry."

Though today you'll rarely find trumpets, shimeji or hen of the woods at mainstream groceries, at Asian markets in Southern California they are year-round staples, almost as common as buttons. And for a specialty ingredient, they're surprisingly inexpensive -- usually less than $10 a pound.

As is common with mushrooms, each of these specialty varieties may be found under several names.

The king trumpets are also called king eryngii, or king oysters (technically they're Pleurotus eryngii, and are closely related to the common oyster mushroom, Pleurotus ostreatus). King trumpets are almost all stem and are large -- commonly 3 or 4 inches long and sometimes as many as 6 or 7. Their texture is firm and meaty and their flavor is mild.

Shimeji (Hypsizygus marmoreus or tessulatus), also called beech mushrooms, look like oversized enoki. However, while the latter are cute but basically flavorless, shimeji have a delicious nutty taste. They come in either white or brown.

Perhaps the most deeply flavored of these mushrooms is the hen of the woods or maitake (Grifola frondosa). Though it isn't as attractive as the king trumpet or shimeji -- it pretty much looks like something you'd find sprouting from the forest floor -- it has a robust earthy, woodsy flavor that is superb.

More than 95% of the mushrooms sold in the United States are from the agaricus family, whether they are common white or brown buttons, the slightly larger cremini or the huge portobello. In reality, those are all very closely related mushrooms harvested at various points in their growth.

Agaricus mushrooms are so popular because they are so easy to grow. Though plants grow in the earth, mushrooms are grown on different bases, called substrates. Sometimes this is very simple. Agaricus will thrive even on straw.

Other mushrooms such as oysters and shiitakes grow on dead logs, making them only a little more difficult to cultivate. The specialty mushrooms Hokto is growing take that a step further, growing on a specially composed substrate -- primarily sawdust, ground corncobs and wheat and rice bran.

The holy grail of fungi culture is the cultivation of such treasured wild mushrooms as chanterelles, porcini, morels and truffles. Though experiments are ongoing and hope springs eternal, this is an exceedingly difficult process because these are mycorrhizal mushrooms. That means they grow only in community with the root systems of living trees, something that is much harder to manage on a commercial scale.

Waste not, want not

OF COURSE, farming mushrooms is nothing new. They've been cultivated for centuries and the introduction of large-scale mushroom growing in the U.S. dates to the 1890s.

It started in the little town of Kennett Square, Penn. -- not far from Philadelphia -- where a Quaker carnation grower named William Swayne began growing mushrooms in the dark areas under the growing tables in his greenhouses.

Because of the town's proximity to the major markets of Philadelphia, Pittsburgh, Baltimore, Boston and New York, this soon became a thriving regional business.

It was also a pioneer in recycling. In those days, most public transportation was by horse, and cleaning up after the beasts was a major problem in urban areas. Since these fungi grow well on straw and manure, the wagons would leave Kennett Square loaded with mushrooms and return loaded with the material with which to grow more.