Tuesday
September
02
2014
12:05 pm
Weather

  Home
  Local News
  State / National / World
  Sports
  Opinion / Letters
  Business
  Arts / Entertainment
  Lifestyle
  Obituaries
  Calendar
  Submit Event
  Comics / Games
  Classifieds
  DJ Designers
  Archives
  Advertise With Us
  About Us
 
 
 
 

Check out our archive of Dining Guides - Yum!

Houseplants wait out the darkest days
January 09, 2014, 05:00 AM By Lee Reich The Associated

Plants and people can’t help but feel a bit wan this time of year, but things are brightening up already. Every day the sun is gradually moving higher in the sky, burning with increasing intensity and duration.

Light is measured in foot-candles — the amount of light cast on a square foot area by a candle at 1 foot distance — and the sun on a clear summer day can bathe us in 10,000 foot-candles. Contrast that with the paltry 500 foot-candles dribbling down on an overcast winter day.

Houseplants’ problems are further compounded by windows, which cut sunlight by another 10 percent. No wonder these plants, if they are growing at all, stretch for light this time of year.

There are ways you can help them.

One is to clean your windows. Any dirt on the glass cuts down light. While you’re at it, dust or spritz off your plants’ leaves; dust has the same ill effect.

Fortunately, many houseplants hail from the shade of tropical jungles. Still, flowering and fruiting take energy, which comes ultimately from the sun, so if you want flowers or fruits from such plants as Jerusalem cherry, flowering maple, citrus and miniature roses, you have to arrange for abundant light. Otherwise these plants will just stay alive, might even grow, but will not flower and fruit.

HOW BRIGHT

IS YOUR WINDOW?

How much light is enough? Most flowering and fruiting plants need 1,000 or more foot-candles, although some, such as African violet, rex begonia, flowering maple, zebra plant and crown-of-thorns, will provide colorful displays even at about 500 foot-candles. Below that level, stick strictly to foliage plants such as cast iron plant, Swiss cheese plant, baby’s-tears, parlor palm, pothos and ferns.

You can translate those needed foot-candles into light measured by a digital SLR camera. Set it on aperture priority with the aperture at f/8 and the ISO at 100. Hold a white sheet of paper so that whatever light you’re measuring falls directly on it, and measure the shutter speed reading that the camera gives you (without a flash) for a good picture from about a foot away. Multiply the shutter speed times 4 for the approximate foot-candles. (Shutter speed is usually expressed as a fraction of a second, so a speed of “500” is really 1/500th of a second; for foot-candles, you’d multiply 500 times 4 for 2,000 foot-candles. If light is very dim, the shutter speed might be more than a second; no need to measure, in that case, because in such light any plant will barely stay alive.)

Take measurements at various locations and times of day; you’ll probably be surprised at how little light falls near even a bright window.

If such exactitude is not your style, just gauge light by window direction. A south-facing window is brightest, followed by east and west-facing windows, with north windows being the darkest. Any obstruction — even a leafless tree — will reduce light levels, as will moving a plant back from a window.

ARTIFICIAL LIGHT CAN HELP, MAYBE

Natural light can be augmented with artificial light. Don’t expect too much from artificial light, though, especially for large plants, the bulk of whose leaves cannot get close to the light source. A fluorescent light, for example, casts as much as 900 foot-candles of light, but that’s only within 6 inches of the light bulb. Light levels drop dramatically as you retreat from the bulb — with the square of the distance, so double the distance and you have only one-fourth of the light, triple it and you have only one-ninth, etc.

In addition to intensity, the spectral distribution of the light can impact plant growth. Flowering requires more light at the red end of the spectrum; fluorescent light tends toward the blue end of the spectrum.

Bulbs other than fluorescents have their own advantages and disadvantages. Incandescent lights convert much of their energy into heat, so you can’t put a plant close enough for a dramatic effect on growth without scorching leaves. Special high intensity lights, such as mercury vapor and sodium lights, can dramatically increase growth, but the intensity and spectrum of the light will make your living room look more like a hospital operating room. LED (light-emitting diode) bulbs also have potential for indoor plant growing. They are efficient, and the spectral output can be tailored to plant needs.

My own plan is to wait out the sun. It’s reassuring to watch plants naturally gather steam as the days grow longer.

———

Online:

http://leereich.blogspot.com/

http://leereich.com/

 

 

Tags: light, candles, plant, plants, window, flowering,


Other stories from today:

 

 
Print this Page Print this Page  |  Bookmark and Share
<< Back
 
Return To Archives
 
  


 
 
 
Daily Journal Quick Poll
 
How often do you go to San Francisco?

Five days a week, I work there
Every weekend
About once a month
Every few months
About once a year

 

 
 
 
 
 
 
Video purports to show beheading of U.S. journalist
BEIRUT — An Internet video posted online Tuesday purported to show the beheading of U.S. journalis..
U.S. home prices rose at slower pace in July
WASHINGTON — U.S. home prices rose in July but at a slower rate compared with earlier this year. T..
U.S. manufacturing grows at fastest pace in 3½ years
WASHINGTON — U.S. manufacturing grew in August at the strongest pace in more than three years as f..
U.S. construction spending up 1.8 percent in July
WASHINGTON — U.S. construction spending staged a strong rebound in July, rising by the largest amo..
More >>  
 
 
  
 
  
 
©2014 San Mateo Daily Journal
Burlingame news