University of Vermont Extension 
Department of Plant and Soil Science

Anytime News Article


Dr. Leonard Perry, Extension Professor
University of Vermont

Potted orchids have become increasingly popular and common in stores.  If you want the plant to continue growing after bloom, and bloom again in future years, choosing the right ones is key.  Also important is the culture, which is a bit different from most other houseplants.

To begin with, orchids vary in their temperature requirements.  Choose those that fit your home environment in winter-- warm-growing ones if it is consistently warm (68-75 degrees) or intermediate-growing if night temperatures are lower (60-65 degrees).  Very important for orchids of all types is high humidity and high light during winter, indirect light during summer.

If you buy an orchid, you may notice it is not growing in soil but rather in bark, a black fiber (roots from the osmunda fern), or similar material.  This is because most orchids are "epiphytic", getting most their water and nutrients from the air through aerial roots.  These are often the white thick roots you see growing from the plant on the surface or even outside the pot, which should NOT be cut off!  Exceptions to the epiphytes are the few that grow in soil (terrestrial) or on rocks (lithophytic).

Many epiphytes have upright swollen stems called "pseudobulbs" which rise from a rooted horizontal stem.  They serve to store food and water.  Examples of these are popular genera such as Cattleya, Dendrobium, Epidendrum, Laelia, and Oncidium.  New pseudobulbs are formed along the horizontal stem, meaning growing is in a horizontal direction.  Such orchids are often called "sympodial".  If these are planted in osmunda, you may need to water every 3 or 4 days.  Water more often if they are planted in bark.

Other epiphytes, such as Vanda and Phalaenopsis, don't have pseudobulbs.  Their growth is upright along a single stem.  Aerial roots come from the stem, often from between the leaves.  These orchids are often called "monopodial".  Since they don't have storage structures either above or below ground, they often need water daily.

When checking for water, never let the orchids dry out completely.  Water well until water is running out the bottom of the pot.  But don't let plants stand in water, as in a saucer.  I find it easier to water pots holding them over a sink or bucket.

Epiphytic orchids are quite sensitive to air pollution, water quality, and too much fertilizer.  If too little fertilizer, pseudobulbs may shrivel and leaves turn light green or yellow.  If leaves are dark green and floppy, and there are no flowers, this indicates too much fertilizer.  Blackened root tips indicates damage from too much fertilizer.

Softened water should not be used, as the salts will damage roots.  Most chlorinated city water sources can be used, although excess chlorine can also damage roots.  The best water to use is distilled water, pure spring water as you often find in stores, or even collected rain water.

Fertilizer varies mostly with type of growing medium, type of and amount of growth.  Plants actively growing, sending out new shoots, will need fertilizer.  If inactive or dormant, as in the rest period with some orchids, don't fertilize.

Plants growing in osmunda need less fertilizer than those growing in bark.  Sympodial orchids, having the pseudobulb storage organs, need less fertilizer than monopodial ones.  Although most houseplant fertilizers will work, you may wish to get one specially formulated for orchids.  Follow label directions for the rate.  A general houseplant fertilizer, applied to plants in bloom or active growth, might be every two weeks for sympodial orchids in bark, every 4 weeks if in osmunda, and twice as often for  monopodial orchids.

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