How to grow Moth Orchids indoors and outdoors

Phalaenopsis Moth orchid Image by Albrecht Fietz from PixabayPhalaenopsis Moth orchid Image by Albrecht Fietz from PixabayDespite their exotic looks moth orchids are easy to grow without much fuss, if you simply give them what they require to flourish. For this reason, these exquisite orchids with their elegant arching sprays of long-lasting blooms are popular among novice and experienced growers alike. Read more about caring for them below.

In order to grow any plant at home, and especially if that plant is not native to your area, it is always helpful to understand the environment and climate in which it grows in its native habitat. Moth orchids are no exception, and although they come from the tropics, they generally like the light and temperature condition of our homes, making them an excellent choice for ‘first time’ orchid growers, and most suitable for city dwellers with limited space. In the warm frost free regions of South Africa, they also grow well outdoors.

Phalaenopsis orchids occur in widely diverse climates within the tropics, with some species occurring in the seasonally dry areas of Thailand or Burma, while others are wet-rainforest species from the Philippines, Malaysia or Indonesia. They are native throughout south-east Asia from the Himalayan Mountains to the islands of Polillo and Palawan of the Philippines, and Orchid Island off Taiwan is named after this orchid. They even occur in northern Australia. 

Phalaenopsis hybridPhalaenopsis hybridIn the wild moth orchids are typically found in tropical lowland forests where they thrive way below the canopy in almost complete shade, and where it is moist and humid. They favour growing on tree branches and between rocks, usually near a source of water for moisture, and which may simple be in the hollow of a tree, where the boughs branch out and rainwater collects, or a depression in a rock.  Aside from rainforests, they are also found in seasonally dry or cool environments, as well and in open grassland areas such as pastures. 

Most Phalaenopsis orchids are classified as epiphytic plants because they attach themselves to other plants - they are not parasitic and derive all their moisture and nutrients from the air and rain. A few are classified as lithophytes because they attach themselves to rocks. 

Phalaenopsis is a monopodial orchid that grows from a single stem, and the flowers emerge from between the leaves. Like other orchids with monopodial growth, they often produce copious aerial roots that hang down in long drapes, and underneath the grey root coverings is green chlorophyll, which is used as an additional photosynthetic organ. Because they do not have a rhizome or pseudo bulbs the species has adapted to dry periods by evolving fleshy succulent leaves instead, and if the plant is happy and healthy, it can produce up to ten or more leaves at a time. However, in home cultivation the plant generally produces about two sets of leaves a year, and the older basal leaves drop off at the same rate, so the plant commonly retains only two to four leaves at one time.

Modern breeding programs have brought about enormous changes in plants for the mass market, with true miniature plants flowering in 6cm pots, to multi-floral types that flower several times a year, and even large plants with enormous leaf spans, and flower stems up to 1m long.

There is a moth orchid for almost any colour scheme, and besides the beloved pink and white varieties, advances in hybridizing have produced gorgeous yellow, red and purple shades, as well as types which are mottled. Although many new hybrids are introduced every year, most Phalaenopsis offered for sale are unnamed hybrids and only specialist orchid growers will offer named species and hybrids.

Growing moth orchids indoors:

If kept in the home, moth orchid flowers usually last two to three months, but mature specimens grown in ideal conditions can bloom for much of the year. An added advantage of growing orchids is that they are one of the few plants that continue producing oxygen at night, and are therefore highly recommended for bedrooms.

Phalaenopsis hybridPhalaenopsis hybridWhen grown indoors it is pertinent to remember that in nature moth orchids are typically fond of warm temperatures between 20 to 35°C, and although they are adaptable to temperatures ranging from 15 to 35°C, at temperatures below 18°C watering should be reduced to avoid the risk of root rot. Flowering is triggered by a night-time drop in temperature of around 5 to 6 degrees over 2 to 4 consecutive weeks, usually in autumn.

One of the most important points to consider when growing moth orchids is light, and although light is quite vital to the well-being of the plant, Phalaenopsis are essentially low light orchids, and direct sunlight will cause the leaves to burn. The leaves should be olive green, and if they are darker it means the plant is not getting enough light. On the other hand, red tinged leaves mean the plant is getting too much light. Once the plant is in bloom you can place it anywhere in your home to show it off, as long as the area is out of direct sunlight and draughts.

Moth orchids like high humidity (60 to 70%) so mist your plant regularly with tepid water and use a shallow tray of pebbles filled with water to increase humidity around your plants, but ensure that the pot does not sit in water. A humidifier is also most effective indoors. The higher the humidity, the more important it is to maintain a good air flow around the roots and leaves. Keep in mind that temperatures close to a window on a windowsill will be colder or hotter than your general house temperature; and fluctuating temperatures can cause bud drop on plants with buds ready to open.

These orchids are usually potted in a well-drained bark mixture but can also be potted in sphagnum moss or mounted on wood. One of the most deadly blunders that new growers make is to overwater, and this  together with bad drainage will cause the roots to deteriorate and eventually rot, killing the plant.

How often you water will depend on the potting medium and how much light and heat your plant receives. Bark retains less water than moss; so if your orchid is potted in bark watering once a week is generally sufficient. Moss retains more water, so watering will be less frequent, or when the moss feels dry. During the growth season, water the plant whenever its exposed roots turn silvery white, usually weekly. During the flowering season, you can cut the water back to every other week.

It is best to water in the morning, and to prevent crown rot, and indoors it is good to wipe away any water which may collect in the centre of the plant. Use tepid water (rainwater is excellent) but do not use salt-softened or distilled water. Let the water run through the plant for a minute or so, and be sure to let the plant drain completely afterwards.

During the growing season fertilise with a specialist orchid fertiliser as directed, but feed sparingly during the winter months. The plants do need the occasional 'flushing out', so with every fourth watering use only plain water (with no fertiliser) to ensure that any potentially harmful accumulations of salts are leached from the potting medium

Phalaenopsis hybridPhalaenopsis hybridWhen the blooms are finished, you can cut the spike down to the level of the leaves and the plant will bloom again within a year. You can also cut off the stem leaving two nodes on the stem (nodes are those little brown lines on the stem below where the flowers were.) One of these nodes may initiate and produce flowers again within 8 to 12 weeks. Continue watering and fertilising while you are waiting for the blooming cycle to begin again. If a plant is large and healthy but does not produce flowers in a reasonable time, then reduce the temperature by 5°C for four weeks, and a flower spike will usually develop.

For healthy root growth, repot every couple of years before the potting mix has started to disintegrate. Do this when the plant has finished blooming but do not be tempted to repot into too large a pot, rather choose a pot just large enough to contain the roots. Do not try to bury the fleshy white aerial roots that extend above the pot, as they are prone to rotting.

Growing moth orchids outdoors:

It is also possible to grow moth orchids outdoors in warm, humid, frost-free, and Mediterranean climates, and if properly cared for they can be among the showiest and most exotic of all garden or patio plants.

Moth orchids are epiphytes and cannot be planted directly in the ground outdoors; rather mount them on trees, wooden stumps or rocks, or grow them in containers, hanging baskets, or raised beds, filled with a potting media specifically formulated for these orchids. When mounting or planting your orchids take extra care to make sure the plants are tilted so that water quickly runs out of the crowns.

Growing plants in sphagnum moss in slatted baskets is another very successful way to cultivate moth orchids outdoors, because for those species that want extra moisture the roots will stay inside the moist moss; and for those which require drier roots, the roots will naturally head out onto the basket surfaces and sometimes even grow completely outside the moss

Moth orchids scorch easily in the sun and should be grown in good light but complete shade. Although they like good ventilation around their roots and leaves, they will need protection from strong winds and excessive rainfall. Moth orchids grown outdoors will also need regular watering during dry periods and fertilising with a specific orchid food. While regular watering is appreciated, wet and soggy roots systems and media are to be avoided. Successful growth outdoors means finding the right balance between humidity, temperature, light, and air flow.