GARDENING : Orchids Run Hot and Cold

Not all orchids need a hot, steamy, equatorial jungle or a temperature-regulated greenhouse to keep them happy. Cymbidium orchids, for instance, prefer nippy nights just like the ones we’ve been having. In fact, without them, they refuse to bloom.

Cymbidiums need at least a 20% difference in temperature between day and night in order to send out flower stalks, according to Paul Brecht of Brecht Orchid Gardens in Costa Mesa. Fortunately for cymbidium lovers, he says, this temperature difference occurs naturally in Southern California.

“Cymbidiums thrive outdoors here,” says Brecht. “You could even use them as landscaping plants.”

The Huntington Library & Gardens in San Marino has been doing just that since 1910. Cymbidiums do well under camellias at the Huntington and even better in shade under tall trees, says Jim Folsom, director of the gardens. Keeping snails from munching all the buds is the gardens’ biggest challenge, he says. “Otherwise cymbidiums are pretty straightforward landscaping plants.”

If this is your first attempt at cymbidium cultivation, however, start in pots, Brecht suggests. The challenge with cymbidiums, he says, doesn’t come from keeping them alive. They’re pretty tough plants, tolerating temperatures as cold as 29 degrees and as hot as 100 degrees.

The trick, rather, is in getting them to flower. The secret here, Brecht says, is light--as much as the plants will tolerate without sunburn. “Bright, filtered light inland, more direct sun along the coast,” he advises.

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While striving for the perfect balance of sun and shade, it’s a lot easier--on both you and the cymbidiums--to move pots around rather than continually uprooting plants.

Bill Austin, an orchid hobbyist in Orange, grows his cymbidiums in a western exposure tempered by the shade of pine and mulberry trees.

“Cymbidiums can take a lot more sun than you’d expect,” he says, responding to surprise at the plants’ bright location. “You know they’re getting enough when they produce bright yellow-green foliage.” (In other plants you’d call this rather bilious color chlorosis.) Foliage isn’t the point with orchids, Austin says; flowers are. And lime-leafed plants bloom; forest-green ones don’t.

When plants put out flower stalks and asparagus-tip-like buds, Austin moves his cymbidiums to a shadier spot so that the sun won’t fade the flowers. “I keep the plants at half-gallon size or smaller,” he says, “so that I can move them around easily without wrecking my back.” Cymbidium foliage also darkens in the shade.

The second secret to cymbidium blooms is never letting your plants dry out, according to Gordon Clayton of Santa Ana, another orchid fancier. “Even though they have back bulbs for water storage, cymbidiums prefer always being damp,” he says. On the other hand, orchid literature warns and Brecht concurs, over-watering is the leading cause of plant failure in cymbidiums. “It causes root rot,” he says.

If you use a porous potting mix that provides plenty of aeration and drainage, Clayton says, over-watering during the dry, sunny growing season (March through October) is unlikely.

The Orange County Branch Cymbidium Society, for instance, recommends watering at least twice a week during this period. Keeping orchids too wet in the winter is where most people go wrong, Clayton believes. Watering once every two or three weeks may suffice during cold weather, says Casa De Las Orquideas, a Solana Beach grower.

What constitutes the perfect potting mix for cymbidiums? Every grower will give you a different answer. Clayton, for instance, uses a combination of fine bark and washed sand in an 80-20 ratio, with a little blood meal, dolomite and steer manure mixed in. Austin, on the other hand, likes bark, perlite and charcoal in a 8-1-1 ratio. And Brecht recommends half orchid bark to half potting soil with a bit of coarse-grade sponge rock stirred in.

Bark chips are the basis of all cymbidium mixes, says the Huntington’s Folsom. Whatever else gets added to the cocktail, he says, depends on the location of the garden--inland growers, for instance, often like to add water-retaining materials such as peat or perlite to their mixes--and also the amount of time gardeners have at their disposal.

“Everybody has their little tricks,” he says, “but I think the more complicated you make things, the less likely you are to follow them. Personally, I like simple mixes.” The Huntington, he says, uses a commercial cymbidium mix formulated for inland locations.

Since bark is an organic material and breaks down, repot every two or three years, Folsom suggests. It’s worth the trouble, Austin says. “You can practically see the plants take off when you give them new material.”

In addition to being well-watered, cymbidiums like being well-fed. The ideal diet is a high nitrogen fertilizer, like 30-20-10, during the growing season (roughly March 1 to Aug. 31) to promote foliage growth, followed by a lean nitrogen formula, like 4-10-10 or 5-25-25 from September to February to encourage flower formation.

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Many orchid growers, however, find it simpler and nearly as effective to fertilize their plants year-round with the same balanced formula fertilizer--something like 18-18-18 or 20-20-20--with an occasional top dressing of bone meal, blood meal or a granular fertilizer like Osmocote for additional nitrogen during the growing season.

“If you want show quality flowers, you need to follow the stricter rules,” Folsom advises. “But, if all you want is pots of handsome flowers to sit around and admire, you can be more casual.”

Whatever route you choose, stick with it, Austin says. Cymbidiums appreciate consistency, he says. He fertilizes his once a week during the summer, every other week in the winter. Other experts advise every second or third watering or every other week.

Follow all the rules, though, and an occasional cymbidium will still refuse to bloom. “I’ve had some five years or more that haven’t produced flowers,” Austin says, “but I’ve finally figured out why. I think (Orchid) society members give away the plants they can’t get to bloom either.”

Is bothering with plants even the people who adore them admit are “persnickety” worth it? Well, have you ever walked by an orchid without stopping? These exotic beauties aren’t ephemeral either. Individual blossoms last two to three months. Even cut flowers last three to four weeks.

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Their flowers not only make cymbidiums worth the trouble, Austin says, they make growing them addictive.

A little chill in the air just warms a cymbidium grower’s heart, he says, because that’s when the orchids spring into action.

“The cool of the evening seems to spark cymbidiums,” Austin says, “and the buds tend to open early in the morning. It makes it fun to walk outside on a chilly morning to see what happened overnight.”