Why Isn’t My Moth Orchid Blooming?

Moth orchids, with their ample blooms on long, arching stems, are a houseplant favorite. Their universal beauty and ease of growing (at least as orchids go) have broad appeal. While Phaleanopsis can bloom more than once a year, it’s possible that they won’t bloom at all without meeting certain conditions.

It can be tough to get an orchid to rebloom after receiving it in full flower. It takes the plant a lot of energy to flower, and optimal light, temperature, and water are key to initiating the process. In their happiest growing environments, they’ll rest post-flowering and garner the energy to rebloom.

Make slow changes to the moth orchid’s growing environment and look for signs of improvement if you aren’t seeing blooms around the same time the following year. Phalaenopsis are good at rebounding, albeit slowly, and can go on to flower for years.

About Phalaenopsis

There are over 60 species of Phalaenopsis, and most that we grow at home are hybrids. The exotic-looking bloomers originate in tropical and subtropical Asia and northeast Australia in moderate, humid growing environments. Bred to be floriferous in a rainbow of colors and patterns (even a glow-in-the-dark one debuted in Tokyo this year), there’s a stunning option for every collection.

In the mid-1700s, botanists like Linnaeus turned their sights to Phalaenopsis as it came into discovery. The early nomenclature differed, but a century later, the genus was in cultivation in Europe. Dutch botanist Dr. Karl Ludwig Blume classified them in 1825 as Phalaenopsis, its own genus of epiphytic orchid. The name derives from the Greek phalaina, “moth,” because of its floral resemblance to white moths in its tropical habitat.

Moth orchids are epiphytes, dwelling in nooks of trees, and lithophytes, growing in rock crevices. Their plump white roots absorb moisture from the air and nutrients from decaying plant material. In an attempt to mirror its natural environment, we may not always get the prime conditions right. The adaptable epiphyte will work with us if we move slowly and patiently, with a reward of long-lasting, exotic blooms.

Gardeners in zones 10 and 11 can leave moth orchids outside year-round (zone 9, too, for most of the year) and expect annual blooms. The rest of us need to enjoy them indoors when temperatures begin to lower in fall.

Not Enough Light

If a moth orchid isn’t blooming, light exposure is the first consideration. The most common cause is insufficient light. Without enough light, the leaves and roots can’t absorb and process the energy needed to flower. But, given too much light, leaves scorch, and buds won’t form.

Fortunately, Phalaenopsis adapts to lower light, making them easier care than some of their cohorts. Medium to bright light is best. It is ideal to place them near an east-facing window, as it provides morning sun and indirect light in the afternoon. In a west or north-facing situation, take care to place pots away from the window’s direct sun or filter it with a curtain or blinds.

Leaves are a good visual indicator of whether or not light exposure is sufficient. If they’re very dark green and floppy or droopy, low light may be the issue. Foliage leans toward grassy green in its natural state and grows more horizontally than lying flat. Or, if leaves are blistered, stunted, and yellow, they’re likely in too much sun. Sun exposure depletes leaves of chlorophyll, and they lose function.

Move those in lower light to a brighter spot, like a windowsill facing a different direction, or outdoors in summer. Err on the shady side rather than too bright, as it’s easier for the orchid to acclimate.

Temperature Change

The epiphytes need a difference in daytime and nighttime temperatures to bloom. In the wild, temperatures may vary from 10-20° between day and night. Phalaenopsis develops flowers in response to a cool period of about two to four weeks with nighttime temperatures of 55-60°F (13-16°C). After this cool period, move it to a warmer spot between 60-80°F (16-27°C) to stimulate flowering. A day-to-night temperature variation of 10 degrees is the sweet spot.

Cooler nights allow orchids to set buds. Setting the orchid near a cool window in fall benefits it with a nighttime temperature drop, as does lowering the thermostat. Keep pots away from drafts to prevent buds from dropping. Heater vents and fireplaces, as well as cold blasts from an open door, disrupt the process.

Watering Issues

With orchids being tropical plants, we sometimes love them to death by giving them too much water. In their rainforest environs, they experience drenching rains followed by periods of drying out. Even the adaptable moth doesn’t withstand prolonged saturation.

Epiphytes need regular water, but since their roots absorb rain and moisture in the air, they don’t acclimate to consistently wet soil. Soggy potting media leads to decaying roots and plant stress as they can’t uptake water and nutrients. Fungal root rot from overwatering is a primary cause of loss, let alone a lack of flowers.

Underwatering is another stressor, forcing energy conservation to survive. Water fluctuations also cause moth orchids to refrain from blooming. Weak roots develop unevenly for less robust upper growth.

How and When To Water

A well-draining container is essential to health, and soilless bark mix is an ideal potting medium. Sphagnum moss is another potting medium sometimes used for orchids, which holds moisture longer.

It’s time to water when the potting media feels dry to the touch at one inch below the surface. Err on the dry side rather than overwatering without allowing media to dry out completely. For bark mix, watering about once a week is likely. Water about every three weeks for orchids in moss to avoid excess moisture. 

Water thoroughly with room temperature or tepid water until it runs through the drain holes. Phalaenopsis is fine with tap water, whereas other orchids are more sensitive to its minerals.

Not Enough Humidity

Moth orchids need humidity at 50% or higher to flower. This is average within most homes, but dry climates and air conditioning and heating reduce available moisture. To raise the humidity, group plants on a tray of pebbles with water. 

The pots should sit above the water to avoid excess soil saturation. The tray and group increase available air moisture. Humidifiers, too, work quickly.

Air circulation is equally important to prevent excess moisture on leaves and stems from promoting disease. With a lack of natural breezes, a fan or humidifier works to increase airflow.

Too Much Fertilizer

In the tropics, orchids receive nitrogen from raindrops and nutrients from decaying plant material on trees. While we don’t have quite as self-sufficient natural nourishment systems at home, fertilizer gives a boost when necessary.

An organic, balanced houseplant fertilizer at ¼ strength every other week works well to promote larger blooms. Once a month, water thoroughly to rinse the roots of any fertilizer salts and deposits.

Fertilize every other watering session in the warm months of active growth. Cut back to every three to four weeks in cool seasons. Fertilizing too much fosters an overload of nitrogen that inhibits blooming, and it’s better to underfertilize than overdo it.

Time to Repot

The tropicals need space and air circulation to flourish. The issue may be the need for a larger pot If roots or new shoots are at the edge of the pot or trailing over.

To repot an orchid, remove it from the pot and potting media. Trim off any brown roots or declining parts. After trimming, It may not need a bigger pot – just add fresh bark mix to its current container. Decaying bark drains less readily and can limit air circulation and oxygen to roots. 

Fresh bark mix initially repels water and benefits from soaking for at least 15 minutes to saturate fully. Some gardeners soak theirs for a few hours for full absorption.

If a larger pot is warranted, opt for one or two sizes bigger. Two big, and there’s room for waterlogged roots with media that stays soggy.

Proper Post-Bloom Care

Setting up your moth for a potential rebloom begins as the initial flowers fade. When flowers drop, the stem dries and turns brown. There are two options when it comes to cutting the stem. One is to remove at the base, allowing the orchid to redirect its energy, restore, and produce a future bloom spike.