University of Vermont
Department of Plant and Soil Science

Anytime News Article
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EASY HOUSEPLANTS—THE PEACE LILY

Dr. Leonard Perry, Horticulture Professor
University of Vermont

This is one of my favorite houseplants, and it has been called by some a “perfect houseplant” as it is one of the easiest to grow and has desirable benefits.  The peace lily gets few pests or diseases, and has no significant problems.  It isn’t fussy about watering, gets by on little fertilizer, and is one of the few houseplants to bloom in low light.
   
The peace lily (Spathiphyllum, said as spath-eh-FILL-um), is in the Arum or aroid family, having a characteristic flower consisting of an outer white shell or “spathe”, and inner white flower cluster stalk or “spadix”.   Actually the spathe is a modified leaf or “bract” surrounding the true flowers of the spadix. The scientific genus name means leaf-spathe, referring to this feature.
   
What we know and call the flowers are generally 2 to 4 inches or more long, are borne above the leaves about 18 to 24 inches high, each singly on a green stalk.  The flower will often last for several weeks, after which you can cut off the stem down near the leaves.  They resemble flags of peace, hence the name. The white flowers also make this plant popular for funerals.
   
These aren’t really lilies at all, but rather a tropical perennial spreading with rhizome roots, more closely related to anthuriums.  Another characteristic of this and other aroids is that the plant contains oxalates that can irritate and burn the mouth if ingested.  So keep it away from any children or pets that may chew its leaves.
   
Leaves are rather long, one to 2 inches wide and perhaps 6 to 12 inches long.  They arise from the soil, and narrow at the tips.  They’re dull to shiny green, depending on the selection.  Being somewhat wide they collect dust, and so will benefit from periodic dusting or washing off in the sink or bathtub.   Washing also will remove any white mealybug pests that might be trying to get established.  The only other pests to watch for, which are seldom seen, are brown scales.
   
Being tropical, peace lilies like humidity.  Too little, and leaf edges and tips may turn brown.  Placing plants on a tray of pebbles kept moist, or near a humidifier, helps them in otherwise dry interior air.
   
The peace lily is rather forgiving if you don’t water properly.  Leaves will start to droop when the plant really dries out, but when watered will rebound.  I’ve been amazed how dry this plant can get, leaves hanging over the pot, and then revive after a good watering.  Just don’t let the plant sit in water too long or become waterlogged, as this will lead to plants wilting too, and roots rotting.  If plants dry out, some leaves will turn yellow; just cut them off near the base of leaf stalks.  Some will yellow too with age. 
   
Don’t place the peace lily in direct sun or the leaves may burn and get brown streaks or spots.  It prefers bright, indirect or filtered light but will survive in low light.  It will even grow fine under strictly indoor lighting if on for at least 10 hours or more.  Plants will flower in low light, just less than in brighter light. 
  
If too low light, however, or plants are less than a year old (including ones recently divided), they may look fine but not flower.  If it flowers but just sparingly, less than when you bought it or than those seen in floral outlets, this may be because growers sometimes use a natural hormone (gibberellic acid) to promote more flowers.
   
Fertilize sparingly, preferably when plants are putting on new growth or blooming, and usually only once or twice a year.  You can fertilize more often, but just at a reduced rate—perhaps half or less recommended on your fertilizer label.  If the flower blooms are rather green, this is a sign plants are getting too much fertility.
   
After several years, perhaps sooner if plants are in a small pot, they may need shifting into a larger pot, or dividing.  Make sure to have several groups of leaves on each division, use a standard indoor potting soil, and don’t fertilize for a few months until roots begin to grow.  Use a very well-drained, porous potting mix such as one containing mostly peat moss, fine bark, and perlite, or similar amendments.
   
Being native to the tropical regions of the Americas and Southeast Asia, peace lilies prefer warmth.  Home temperatures are generally fine for them, their preference being for 65 to 75 degrees (F) during day, and up to 10 degrees cooler at night.  They will, however, tolerate a bit more of a range, or even rather consistent temperatures as in many office or public settings.  Just don’t let them get below 50 degrees, or even below 60 degrees for more than a day or two.
   
In addition to being attractive, the peace lily is one of the indoor plants that studies have shown help purify air from pollutants—known as “phytoremediation”.  Dr. Dennis Wolverton worked with NASA for many years studying many indoor plants for these properties, primarily for enclosed space stations but with results applicable to our interior environments on earth.  Peace lily was among the tops for removing chemical air pollutants such as carbon monoxide, formaldehyde and benzene, often found in interior living spaces from substances such as paints, furniture varnishes, and carpeting. It can help remove acetone too, as from electronics and adhesives, and even mold spores as one may find in bathrooms.
   
Although there are over three dozen species naturally occurring, most plants that you find for sale are hybrids of these species, and most are now propagated by tissue culture labs.  Available at most outlets that sell houseplants, peace lilies come in a range of sizes, from about one foot high and wide, up to 3 feet or more tall and wide. 
  
There are several named cultivars (cultivated varieties), although you often don’t find them in stores named.  The smaller versions (like the 6-inch high ‘Petite’) are good for tabletops, the medium-sized (like the popular ‘Clevelandii’ with glossy narrow leaves, and ‘Mauna Loa’ whose flowers turn green with age) for plant stands, and the largest ones (like ‘Sensation’) placed on the floor (in a decorative pot, basket, or saucer).  There is even a small popular version (‘Domino’) with leaves splashed with white variegation.

Whether you’re a new gardener looking for an easy beginner plant, or an experienced gardener looking for an attractive, multifunctional houseplant, peace lilies are a great choice.


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