Plant Doctor Archive

Moth orchids sulk

Question I AM very fond of moth orchids and have bought several plants. But after flowering I don’t have much luck — the leaves turn yellow and die off.

Answer MOTH orchids (Phalaenopsis) are from the tropics, so they need more critical care than the relatively easy-care cymbidium orchids that we can grow outdoors in many areas. Temperature and water are the most important factors. To grow well they need a minimum of 16–18°C, but ideally 20–25°C. If it gets too cold you’ll get slow growth or no growth, leaf yellowing, possible leaf spotting and, in extreme cases, leaf drop. Similarly, too much water, especially if the temperature is cold, will cause root rot and leaf drop.

It sounds like you may be over-watering your plants. Also, you must not leave them standing with their roots in water for too long.

Although all this may sound difficult, it isn’t really. Moth orchids make good indoor plants in a well-lit room and will stand the odd cool temperature as low as 10–12°C, as long as you keep them on the dry side at those times. And they’ll generally flower each year with spikes of long-lasting blooms. Feed every couple of weeks during summer with a general liquid fertiliser. For more detailed information, check out www.rnzih.org.nz/pages/Moth-orchids.htm

Weekend Gardener, Issue 204, 2006, Page 38