A Phalaenopsis orchid (Phalaenopsis spp.) provides long-lasting, exotic blooms for the home and outdoors in U.S. Department of Agriculture plant hardiness zones 10 through 12. Also named a moth orchid for the shape of its flowers, this tender plant grows best in warm, humid, free-draining conditions and bright, indirect light. In the wild, a moth orchid naturally grows on the trunks and branches of trees.
Watering a Moth Orchid
Accurate watering is essential when caring for a moth orchid. Overwatering the plant and allowing it to stand in water cause root rot diseases. A moth orchid container must have drainage holes.
Fill a container with tapwater and allow it to stand until it reaches room temperature. Water a moth orchid with the water in the morning when the potting mix is slightly dry on the surface. Stand a moth orchid in a container in a sink, and slowly pour water over the potting mix until it flows through the drainage holes. A mature moth orchid usually needs water about once a week, but in hot summers it may need water every other day. When temperatures are low a moth orchid may need water only every 10 days.
A moth orchid usually grows in a bark-based potting mix, and needs a high-nitrogen fertilizer. Bark potting mixes retain little water or plant nutrients. A 30-10-10 fertilizer supplies a moth orchid's needs.
Dilute a liquid 30-10-10 fertilizer at a rate of 1/4 teaspoon per 1 gallon of room-temperature water, and apply the solution to the moth orchid potting mix in the morning every two weeks while the plant is actively growing. You can apply fertilizer in place of water if the plant needs watering. When the moth orchid isn't producing fresh growth, apply the diluted fertilizer once every four weeks. Don't allow the fertilizer solution to touch the orchid's leaves. Dilute a 30-10-10 fertilizer at a rate of 1 tablespoon per 1 gallon of water to fertilize an outdoor moth orchid.
Pruning for Flowers
Pruning a moth orchid's faded flower stalk often produces a second flush of flowers. Moth orchid flowers last four months or longer, and blooms can appear repeatedly throughout the year.
Sterilize your pruning shears by wiping the blades with a cloth that was dipped in rubbing alcohol, and prune a moth orchid's flower stalk when the final flower fades. Prune below the lowest flower and just above a slight bump on the stalk, which is called a node. The second flower stalk usually sprouts from the node. When all the flowers on a moth orchid have faded, prune the flower stalk to 1 inch long.
Treating Pests and Diseases
Mealy bugs and scale insects can infest an indoor and an outdoor moth orchid, and an outdoor orchid may also attract slugs and snails. Viruses, which cause discoloration and distorted growth, can also affect this plant. A plant suffering from a virus should be thrown in the trash.
Mealy bugs secrete a cottony coating, and scale insects look like tiny shells on an orchid's stems and leaf veins. Spray an indoor or outdoor plant with an insecticidal soap spray, avoiding the blooms. Spray an outdoor plant on an overcast day. Spray the orchid every week, if necessary.
To control slugs and snails on an outdoor moth orchid, go out after dark with a flashlight, and pick off and destroy all the slugs and snails you see.