How to Grow and Care for Clamshell Orchids

Orchids are a wild and wonderful family of plants comprised of nearly 800 genres and over 28,000 individual and naturally occurring species. This is to say nothing about the countless varieties of hybrid orchids. Clamshell orchids are members of the Prostheceae genus, which includes more than 100 species.

This interesting and beautiful plant can be difficult to find in the wild, but thanks to the internet, it has become much easier to locate in cultivation. Let’s dive deep into these fantastic orchids and discuss how you can grow and care for your own clamshell orchid. 

What are Clamshell Orchids?

Clamshell orchids, also known as Prosthechea cochleata, are one of only a few types of tropical orchids considered native to the United States. These late fall and winter bloomers flower for several months and are considered self-pollinating. 

Mostly native to swamps, woodlands, and damp forests, this epiphyte makes its home on the branches of trees. It is possible to see these orchids in their natural habitat covered in algae or moss – if you can find them! They tend to be difficult to find in the wild but are not considered threatened. 

History

Prothechea cochleata was one of the first orchids to be recorded blooming in a British nursery when one first unfurled its flowers at the Kew Gardens in London in 1787. This sparked a long period of avid orchid collection and cultivation in Europe, with some danger risked in the acquisition of these interesting plants.

Native Area

Clamshell orchids are native to the Americas. It is the national flower of Belize, where it is known as the black orchid. It is found mainly in Central America, the West Indies, Colombia, Venezuela, and southern Florida.

The orchid is considered threatened here in the United States, where it is only native to the southernmost parts of Florida. It predominantly lives in the Everglades, a heavily forested swamp that occupies much of the lower peninsula. 

While it can be difficult to find in the wild, it is common in cultivation. It is prized for its relative ease of care and its very long-lasting and uniquely shaped flowers. It has been hybridized extensively as well. 

Characteristics

Clamshell orchids are sympodial epiphytes. Sympodial orchids grow horizontally along a central rhizome at the base of the plant. The rhizome sends up pseudobulbs, each producing leaves and a single flower stalk. For this orchid, the flower stems continue to grow and bloom rather than dying off after the initial flowers are spent. 

Epiphytic plants are essentially air plants. These are plants that grow attached to tree branches. They do not root in the soil, so they collect all the moisture and nutrients they need from the rain and the humidity they are surrounded by. 

Each pseudobulbs produces between one and three long, straplike leaves that are flexible and typically keel over as they mature. Each also produces a flower spike that can form anywhere between one and 15 flowers.

The blooms are unique in several ways. For one thing, they have a non-resupinate labellum, which sits at the top of the flower rather than twisting around below the petals and sepals. The petals and sepals are long, thin, and twisted, hanging below the labellum, giving the flower a squidlike appearance. 

The labellum of this orchid is very pronounced and usually dark purple in color. Several varieties have striped labellums. The petals and sepals are yellow to pale green and sometimes white. The flowers are not always fragrant, but when they are, they have a spicy aroma. 

Uses

Orchid flowers are edible and decorative and can be often used as a garnish in fine dining establishments. However, the main use of orchid plants is ornamental. These orchids are nearly always sold for cultivation and visual appreciation. 

Where to Buy Clamshell Orchids

You may happen upon one of these orchids at a nursery or orchid show. However, if you want to purchase a clamshell orchid, I recommend looking online. While they are easy to care for and popular, they are not commonly encountered in most brick-and-mortar retailers. 

Planting

Unless you live in the orchid’s native range, which is zones 10-13, your orchid will need to be grown in a container and brought indoors for the winter. Orchids are very cold-sensitive and cannot survive winters in non-tropical climates. 

Beyond keeping it out of the cold, the most important variable in planting an orchid is good drainage and air circulation around the roots. Three different types of specialty orchid pots can be commonly found commercially.

How to Grow

Clamshell orchids are considered easy to grow if their needs are properly met. Let’s explore those needs so we can properly care for these fun plants. 

Light

Like most orchids and other epiphytes, clamshell orchids do not appreciate direct sunlight, as their leaves are sensitive to light and adapted to receiving light through the filter of a tree canopy. For this reason, it is important not to place your orchid in a position where it will be exposed to direct sunlight, especially in the afternoon when the light is more intense. 

Bright, indirect sunlight is ideal for these plants. Setting them near, but not directly in front of, a brightly lit window is a good idea. You can also create a filter by using a sheer curtain or privacy film on the window. My orchids seem to love sitting in the window of my bathroom, which has privacy glass. This disperses the light, making it less intense but still quite bright. 

Water

This orchid appreciates moisture but is surprisingly drought-tolerant for a plant of its type. During their growing and flowering season, which spans from summer through winter, they should be watered about once per week. After flowering, reduce watering to every two to three weeks to avoid overwatering. 

The main cause of death for indoor orchids is root rot. This is caused by overwatering as the potting material breaks down and decays, leading to the perfect environment for bacteria and fungus around your plant’s roots. 

Prevention is the best remedy to prevent the risk of root rot. You can avoid this problem by only watering when your potting material is dry to the touch. If a week goes by and the potting mix is still damp, hold off on watering for another day or two. 

If you keep your orchid outdoors during the warmer months, you will likely need to water it more frequently. I water my outdoor orchids once every three days to keep them from drying out. 

Soil

Orchids don’t grow in conventional soil in nature, so naturally, they need something a bit different in cultivation as well. Most orchids come from the grower in bloom and in a plastic nursery pot filled with damp sphagnum moss. While this will be fine while the plant is in bloom, once the flowers fall and the plant goes dormant, this will hold too much moisture and lead to that dreaded root rot. 

Once your orchid drops its flowers, it is best to repot it. Repotting is not recommended while the plant is in bloom, as it can shorten the life of the flowers. Pot your orchid in a potting medium that includes two parts bark and one part charcoal or perlite. The charcoal absorbs and holds nutrients from fertilizer for the plant to use later. 

If you prefer not to make your potting mix, great alternatives are easy to find at any orchid retailer and even most hardware stores. Orchid bark comes pre-mixed and ready to go in the pot without any fuss. 

Temperature and Humidity

Clamshell orchids are particularly sensitive to cold. While most orchids are native to zones 9-12, this one won’t survive outdoors north of zone 10. It will be happiest with a night temperature in the 60s and a daytime temperature of about 80°F. 

If you notice the tips of your orchid’s leaves looking dry and brown, there is a good chance it needs more humidity. Orchids are tropical and grow in humid environments. This particular orchid is happiest with an ambient humidity level between 50-70%. 

Since this is higher humidity than most people are comfortable keeping in their house, you can do a few things to increase the humidity around your plant. A pebble tray is a good method of increasing the humidity directly around the plant. A humidifier does a great job as well. I prefer to keep my orchids in the bathroom, as the humidity level tends to be higher there. 

Fertilizing

Orchids are heavy feeders that love to be fertilized. You should fertilize once every two weeks or every other watering during your orchid’s growing season. You can find specialty orchid fertilizers that work very well at most retailers or dilute an all-purpose fertilizer. A 20-20-20 formula, for example, should be diluted to ¼ strength and a 10-10-10 to ½ strength. 

When watering and fertilizing orchids, the best method is to water from the bottom. I fill a large tub or sink with water and fertilizer solution and set my pots directly into the water for about five minutes. This way, the plant absorbs all the water it needs, and you avoid water sitting in the crown and leaves of the plant, which can cause rot. 

Maintenance

Orchids don’t require much maintenance or pruning. You must repot your orchid every few years as it outgrows its container. Since this is a sympodial orchid, it will outgrow its container sooner than a monopodial orchid, which grows vertically, would need. 

When repotting, place the oldest pseudobulbs against the side of the container, allowing room for the plant to continue to grow horizontally. Don’t detach the old pseudobulbs unless they are brown and dried out, as these store nutrients for the new growth and flowers that the plant produces. 

Pruning is typically not necessary, with a few exceptions. Any dead or diseased foliage should be removed from your orchid to prevent fungal infection. Also, when the inflorescence has stopped blooming and all flowers are spent, wait until the stem turns brown and then cut it off just above the first node. 

The node is located about an inch above where the stem attaches to the plant and looks like a slight swelling in the stem. Cutting the stem helps the plant redirect energy away from flowering and into new growth.

Propagation

Orchids can be propagated in a few ways, but I prefer division for sympodial orchids. They tend not to produce keikis, or baby plants, as readily as monopodial orchids and are very easy to divide. When you repot your orchid, it is the best time to divide the plant.

Cut through the rhizome at intervals of no fewer than four pseudobulbs. The new plants need the nutrients these spent pseudobulbs contain to establish themselves and produce new growth. Repot your divisions as you would a mature plant and place them in bright, indirect light.

Common Problems

Orchids are not without their issues and can fall prey to some ailments and problems. It could be one of these issues coming to light if you notice your orchid looks unhappy or as though something is munching on it.

Root Rot

This is the orchid grower’s nemesis and the thing that takes out a majority of indoor orchids. Root rot starts in the roots but will ultimately kill your plant if you don’t catch it early in the game. The best way to deal with root rot is to avoid it at all costs. 

The way to avoid root rot is to avoid overwatering. When the orchid potting medium stays damp, it breaks down faster and becomes a breeding ground for bacteria and fungus. Under the bark, root rot appears as mushy, black root tissue that falls apart easily. 

Above the roots, root rot manifests in yellowing leaves, lack of flowers, and leaf loss. The yellowing will first occur close to the plant’s crown and move outward. It is very difficult to save an orchid from root rot, but if it is not advanced, you can trim away the diseased root tissue and repot it in a clean potting medium.

Insect Infestation

Orchids produce lots of nectar and are filled with sweet sap insects love to feast on. Aphids, mealybugs, spider mites, and thrips are all culprits of sucking the life out of your orchids when they happen upon one. These insects drain the plant of nutrients and leave behind a sticky mess called honeydew. 

Honeydew is insect excrement, and it causes some serious issues. For one thing, it attracts ants, but that won’t do much damage to the plant. Honeydew is a perfect environment for black sooty mold to grow, and this interferes with photosynthesis, which is a much more serious issue. Fortunately, the honeydew can easily be wiped away with a damp cloth. 

Leaf Spots

There are a few different pathogens that cause leaf spot in orchids. Most of them are waterborne and can be avoided by watering from the bottom and isolating any plants that may be infected. A few small spots are unlikely to do much harm, but larger lesions could cause a problem, and those leaves should be removed. 

Frequently Asked Questions