How to keep a moth orchid alive

Gardening columnist

To some minds, the poinsettia is cheapened by its ubiquity. But somehow that everywhere orchid — the phalaenopsis or moth orchid — always seems elegant and exotic, even when herded in the big-box store or supermarket.

Mass cloning techniques and industrial-scale propagation in places like Taiwan have kept the market well-fed with unnamed varieties — big whites, pinky purples and weird bicolors — that seem as abundant and non-seasonal as potatoes. Still, the tree-dwelling jungle plant lends grace to its surroundings, the condo lobby, the swanky restaurant or your kitchen countertop. Does anyone not like a moth orchid?

Adrian Higgins has been writing about the intersection of gardening and life for more than 25 years, and joined the Post in 1994. He is the author of several books, including the "Washington Post Garden Book" and "Chanticleer, a Pleasure Garden." View Archive

But this affection, I wager, is accompanied by an underlying anxiety that we will kill the plant through neglect or abuse. Getting the most from a moth orchid — eight weeks of bloom and repeat flowering in a few months — is not difficult but requires method.

In search of the best advice, I traveled to the Floradise Orchids greenhouse of Janet Cherchuck and Stephen Shifflett in Gordonsville, Va., where the couple has been raising orchids commercially for more than 30 years. (They sell at two D.C. farmers markets, regional orchid shows and from their greenhouse 100 miles south of Washington.)

Moth orchids have light and temperature needs, but the single biggest reason they crash, said Cherchuck, is through incorrect watering: usually overwatering, sometimes underwatering, or a combination of the two. Typically, the roots begin to rot and the leaves grow limp.

Getting it right is complicated by the type of growing medium used: either a loose mix of pine bark or sphagnum peat moss. In either case, the orchid should be thoroughly watered and not watered again until nearly dry. The more densely packed moss takes longer to dry and may need watering every 10 to 14 days compared with the weekly pine bark watering, but the timing varies by light levels, warmth and humidity. Use your finger to probe about an inch into the pot to see if the surface is dry. Another way to tell: A watered pot feels heavier than one that is dry.

At a sink, run the orchid under a tap of room temperature water — neither hot nor cold — and let at least a gallon run through the drain holes to ensure complete saturation. With open-growing media in free-draining pots, “watering is about frequency, not quantity,” said Cherchuck. Feed with a weak soluble fertilizer after watering. It’s okay to get the leaves wet, but not the flowers. Finally, tip the plant to remove water from the leaf bases and crown, where the stem meets the roots.

Once the flowers have finished, you can cut to just above a node to promote a new flowering stem. This will appear in a few weeks if the plant is happy. This constant blooming, however, will stress the plant, and the subsequent blooms will be smaller and fewer. If you want to build up your orchid for long-term cultivation, cut off the flower stem and in June, place the orchid outside in a shady, sheltered spot away from direct sunlight. Continue to water and feed as the growing medium dries; don’t rely on rainfall. The required difference in day and night temperatures outside will encourage the plant to bloom after you bring it back indoors in early fall.

Small phalaenopsis varieties, with different bloodlines, can bloom more freely than large hybrids and are a good choice for apartment dwellers who have no yard for summer care.

Buying a moth orchid

Orchids can become stressed if mishandled or improperly kept. Orchids in grocery stores tend to be too cold and displayed close to produce. Nearby apples, bananas or other fruit give off ethylene gas, which causes the orchid blooms to age prematurely.

Look at the general health of the plant. Look for fleshy, live roots. The leaves should be green, turgid and the central growth stem upright. Avoid plants with yellowing tips to the flower stem or with buds that are falling off. Choose an orchid that has begun to flower, not just in bud. When stressed, the buds will be small or fail to open.

Repotting

Moth orchid roots are meant to wander out of the pot. But if the plant is potbound at the base or if the growing mix has broken down and smells musty, repot the plant. This is best done after flowering in late spring. Remove all the old mix, cut off shriveled dead roots and use fresh mix. The roots should occupy about three-quarters of the volume of the new pot — typically about an inch bigger in diameter than the old pot. Placed in a pot that is too big, the orchid will suffer root rot. If your orchid is part of a larger florist’s arrangement, wait for the plant to finish flowering and then pot it individually in a container of the correct size. Moth orchids do not grow by rhizomes and do not need to be divided like other orchids.

Bark... or moss?

Bark:

Pros-

Makes for tougher plants. Reduced risk of overwatering. Easier to see state of roots.

Cons-

Needs watering more often. Harder to tell if it is wet enough.

Moss:

Pros -

Plants grow larger. Looks attractive. Surface lightens when it dries out.

Cons-

More prone to waterlogging. Risk of compacting when repotting. Slight risk of skin disease from moss-borne fungus; wear rubber gloves.

Temperature and humidity

Typical room temperature is fine, but go no lower than 60 degrees. Raising humidity in winter is a boon to orchid and orchid grower alike, but correct watering is more important than high humidity. Misting is unnecessary and may damage the blooms.

Light

Moth orchids like bright, indirect light. Direct sunlight will turn the leaves pale green or yellowish green and stress the plant. Insufficient light will cause the upper leaves to be smaller than the ones below (they should be larger).

Watering

Forget the dainty watering can. Take the orchid to a sink and run water through the pot thoroughly. This will saturate the medium and wash out old fertilizer salts. Test dryness with your finger and learn to judge the watering need by the weight of the pot.

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