Home Cultivation of Orchids

The two most common genera of orchids that are sold for home cultivation are the Phalaenopsis and the Oncidium. Phalaenopsis is also known as the moth orchid because the flat, lobed flower resembles a moth. The genus name comes from the Greek words ‘phalaina’ which translates as moth and “opsis” which means appearance.

Phalaenopsis has about 63 recognized species and more hybrids than can be counted. The genus is native to tropical Asia from southern India and Nepal, east to Papua New Guinea, north to China and Taiwan, and south to tropical Australia.  Oncidium is whimsically referred to as the dancing lady orchid in reference to the small multitude of delicate flowers that flutter up the stem. They are said to resemble a dancer with a flared skirt and tiny waist. Both will bloom in the home and will grow on a window sill with little specialized care.

Phalaenopsis is a “low light” orchid. It grows best of an eastern or southern windowsill. On a brighter sill, a sheer curtain should be used as a screen. The light is proper if there is a soft edge on a shadow cast by a hand or other object. The leaves on a Phalaenopsis should not be a very dark green. This is an indication that the orchid is not receiving enough light to start the blooming process. Direct sunlight will burn the leaves. Brown to black spots on the leaves are an indication of burning. This will also often happen when a leaf has direct contact with the edge of a pot.

Like most orchids Phalaenopsis likes to grow in a medium that drains readily. Most of these orchids are epiphytes so they do not like having their roots wet or contained. Soak well once a week and allow to dry out before watering again. If you bottom water do not leave water in the tray for more than a few hours or overnight. Extensive soaking will rot the roots.

Daytime temperatures of 75°-85°F suit the Phalaenopsis group. Night time temperatures should range from 60°-65°. Deviations from these temperatures will probably not hurt the plant but will interfere with blooming.

If your house is very dry you may want to increase the humidity around your orchids. While 50-75% humidity is said to be ideal, I find that they grow and bloom just fine with a lower humidity. Grouping plants will raise humidity or set them in a tray with stones that are kept damp. Misting is not really advisable for orchids. The water on the leaves can act as a prism and burn the leaves. It can also cause the spread of disease.

Orchids are not heavy feeders so use fertilizer sparingly. It is best to purchase fertilizer formulated for orchids as it is urea free. There are various arguments against the use of urea as a nitrogen source for orchids. One is that it won’t break down in orchid medium, which lacks bacteria common to soil, to free the nitrogen for the use of the plant. Another is that it lowers the pH of the medium. Fertilize weekly or bi-weekly with a half strength fertilizer or monthly with a full strength dose. In the summer use a high nitrogen fertilizer to promote leaf growth. Use a high potassium fertilizer in the cooler moths to promote budding. I probably fertilize every 3 or 4 months and my orchids still bloom. They might indeed bloom better if I fertilized more diligently.  Excess fertilization or even normal fertilization can cause salts to build up in the medium and on the pots. If you fertilize frequently the pots should be flushed with plain water occasionally to remove the salts. Phalaenopsis don’t seem to care much what kind of water is used on them, although there are different types of orchids that a very fussy about water source.

A Phalaenopsis will often bloom twice a year. It will bloom on the same flowering stem. You can either leave it intact or cut it half way back. Cutting it will often induce a second wave of blooms. The flowers are long enduring and frequently will last for a month or more.

It is somewhat harder to specify the needs of Oncidiums as they come from such diverse environments. There are about 330 species that are mainly found in South America, Mexico, the Caribbean and Florida.  Oncidiums will generally grow in brighter conditions than the Phalaenopsis. They will take direct sun light in moderation. A window that receives the morning sun is ideal for Oncidiums. They like bright, to very bright conditions.

They also need more water than the Phalaenopsis. They should be watered before they are completely dry, although they will forgive you if you let them dry out. Most have pseudobulbs that store water to carry them through dry seasons in their native climes. If the pseudobulbs shrivel the plant is not getting sufficient water. If a plant produces a crinkled leaf this is another sign of insufficient watering. These leaves will never straighten out. Excess watering results in rotting roots and pseudobulbs. Do not mistake the normal browning of old pseudobulbs for rotting.

Oncidiums come from a number of different habitats from semi-arid regions to cool misty highlands. Generally, the yellow/brown Oncidiums that are sold commercially are warm growing orchids that thrive in daytime temperature of 80°-85° and nighttime temperatures of 50°-60°. Temperatures that drop below 50° will slow their growth. Oncidiums will also grow with less humidity than other orchids. A 30%-60% range is adequate.

Fertilize in the summer when the plant is actively growing using a weaker fertilizer if you fertilize more often. These plants grow quickly so they do require a bit more fertilizer than Phalaenopsis. Make sure the medium is damp when fertilizing to prevent root burn. Taper off fertilizing in the winter months when the plant is not in active growth. In our area these plant generally bloom after the Phalaenopsis.