Orchid myths: ice cubes, watering, roots, blue orchids… true or false

Daniel Platteau

In short: the orchid found everywhere, Phalaenopsis, is much easier than people think, but it carries a reputation full of false ideas. No, it is not a parasite. No, you should neither cut nor bury its aerial roots. No, blue orchids are not natural. And watering with ice cubes, often mocked, has been tested: it does it no harm. Here are ten common beliefs, checked one by one.

These beliefs mainly concern Phalaenopsis, the "moth orchid". It is by far the best seller: at the Dutch auction Royal FloraHolland, nearly nine potted orchids out of ten are Phalaenopsis (AIPH, 2021). For other easy species, see our top 10 orchids for beginners.

1. "Orchids are parasites"

False. Phalaenopsis is an epiphyte: in the wild it grows clinging to tree branches, but takes nothing from them. It only uses them as a support to reach the light, and its roots capture rainwater and the nutrients that run down the bark (RHS, n.d.). A parasite, such as mistletoe, instead draws water and minerals from its host.

This way of life explains almost all the good practices that follow.

2. "An ice cube a week is the right way to water"

Neither miracle nor disaster. Many gardeners laugh at the idea: a tropical plant with ice? Researchers at Ohio State University and the University of Georgia tested it. For four to six months, 48 orchids received three ice cubes a week, and 48 others the same amount of room-temperature water. Result: no difference in flowering time, leaf health or root weight. The bark dropped to 11 °C, without damage (South et al., 2017).

So ice cubes are not dangerous for a Phalaenopsis grown in bark. Their benefit is mainly practical: they prevent overwatering. But three ice cubes is not much water: in a warm, dry flat, soaking the pot remains more reliable.

3. "An orchid needs water once a week, full stop"

Half true. Once a week is a good rule of thumb in the growing season, a little less in winter (RHS, n.d.). But the right frequency depends on warmth, the pot and the age of the bark. Better to look at the roots:

• silvery grey: they are thirsty;
• bright green: they are full of water, no need to water.

The simplest method: soak the pot for about ten minutes in tepid water, rainwater if possible, then let it drain completely. The roots must never sit in water in the saucer or outer pot, and water must not stay in the heart of the leaves (RHS, n.d.; University of Maryland Extension, 2023).

4. "Roots growing out of the pot are diseased and must be cut or buried"

False. Aerial roots are normal: in the wild, they anchor the plant to the tree and take up moisture from the air. Do not cut them or push them into the compost (RHS, n.d.; University of Maryland Extension, 2023). Only dry and hollow, or brown and mushy roots can be removed.

5. "You can repot it in ordinary potting compost"

False, and serious. Potting compost, even good quality, stays wet and suffocates the roots: according to the RHS, it kills Phalaenopsis (RHS, n.d.). It needs an airy, bark-based orchid mix. Bark breaks down over time and holds more and more water: replace it every one to two years, when the plant is growing (green root tips). A transparent pot, only just bigger than the roots, lets you see the moisture and lets light reach the roots, which also photosynthesise.

6. "After flowering, cut the stem at the base"

Not necessarily. While the stem stays green, cut it just above the second node (the small bumps along the stem) below the faded flowers: a new flowering shoot may grow from it. If the stem turns yellow and dries, then cut it at the base (RHS, n.d.; University of Maryland Extension, 2023). Cutting a still-green stem at the base is not a mistake either: the plant rests and will flower on a new stem later.

7. "It will never flower again"

False, but it needs a signal. A healthy orchid that does not rebloom often lacks light, or coolness. The RHS advises moving the plant somewhere about 5 °C cooler for a month or so: a new flower stem should appear (RHS, n.d.). In practice, a less heated room in autumn, with cool nights, is often enough.

8. "An orchid needs full sun"… or "a dark corner"

Both are false. Phalaenopsis likes bright but indirect light: an east- or west-facing window is ideal. In summer, direct sun scorches the leaves; in winter, a sunnier windowsill is fine (RHS, n.d.). The leaves tell you: light green is good; dark green and stiff means too little light; reddish or yellowish means too much (University of Maryland Extension, 2023).

9. "Blue orchids are a rare variety"

False. The bright blue Phalaenopsis sold in garden centres are dyed white orchids: a dye is injected at the base of the stem and travels up to the flowers. If the plant reblooms, the next flowers will be white (Iowa State University Extension, n.d.). In 2013, researchers at Chiba University in Japan did produce a naturally blue Phalaenopsis by adding a gene from Commelina, but it is not on the market (Greenhouse Grower, 2013).

10. "Orchids are toxic to cats"

False for Phalaenopsis. The ASPCA animal poison control centre lists it as non-toxic to dogs, cats and horses (ASPCA, n.d.). That does not mean a cat can nibble the plant without risking mild digestive upset, or drink watering water full of fertiliser. And not all plants sold alongside orchids are harmless: amaryllis, for example, is toxic to animals (see our article on amaryllis).

The essentials in a table

Test yourself

Sources

AIPH. (2021). Upbeat mood at 2021 Dutch Orchid Inspiration Days. FloraCulture International. https://aiph.org/floraculture/news/upbeat-mood-at-2021-dutch-orchid-inspiration-days/

ASPCA. (n.d.). Phalaenopsis orchid (Toxic and non-toxic plants). https://www.aspca.org/node/5240

Greenhouse Grower. (2013). Genetic modification produces true blue orchid. https://www.greenhousegrower.com/?p=53037

Iowa State University Extension and Outreach. (n.d.). How are blue orchids made? Yard and Garden. https://yardandgarden.extension.iastate.edu/faq/how-are-blue-orchids-made

Royal Horticultural Society. (n.d.). How to grow Phalaenopsis (moth orchids). RHS. https://www.rhs.org.uk/advice/profile?pid=388

South, K. A., Thomas, P. A., van Iersel, M. W., Young, C., & Jones, M. (2017). Ice cube irrigation of potted Phalaenopsis orchids does not decrease display life [Poster]. ASHS 2017 Annual Conference. https://ashs.confex.com/ashs/2017/webprogramarchives/Paper26192.html

University of Maryland Extension. (2023, March 13). Care of Phalaenopsis orchids (moth orchids). https://www.extension.umd.edu/resource/care-phalaenopsis-orchids-moth-orchids