Wednesday, January 09, 2008
Mulch choice depends on climate, topography and traffic
John Arbogast
Landscape consultant John Arbogast answers your questions every Thursday. Send questions about your lawn, garden, plants, or insects to:
Dear John
5102 Greenfield St. SW
Roanoke, Va. 24018
Or send an e-mail. Answers will be given only in this column. Please don't send pictures or samples.
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Q: Which is better, bark mulch or pine needle mulch?
A: Both are excellent mulches, so making the choice depends on where in the country the landscape is and what landscape plants that you want to mulch. Adaptations vary with the topography to be covered with mulch and how much, if any, traffic that the landscape bed is expected to receive.
Pine needle mulch is more frequently used in areas of the country where long-needle pines are common. Here in Roanoke, the long-needle pine called the Loblolly Pine is not suited to our potential lowest winter temperatures. However, in Tidewater Virginia, Loblolly Pines grow well and pine needle mulch is commonly used and not outrageously priced.
Pine needle mulch is thought to be good around acid loving plants like azaleas. The decrease in soil pH due to this mulch might be rather small, though.
I have not seen any data on the difference in flammability of bark mulch versus pine needle mulch. I would think that pine needle mulch could have a greater fire risk because of its fluffiness or airiness. Thus, pine needle mulch could be a poor choice in public areas where smokers gather. However, I do recall seeing fires in bark mulch here in Roanoke.
One more negative trait I’ve seen with pine needle mulch is its moveability on a sloped or very windy site. Also, pine needle mulch is easily kicked out of a landscape area such as along a landscape path or bed which can have pet or people traffic. Maintaining a neat mulch edge can require a little more work in these cases.
Bark mulches are frequently used in Roanoke. The important consideration is to match the kind to the slope and activity of the site. Shredded bark mulch stays in place more readily compared to bark nugget mulches.
Both pine needle and bark mulches have a lifespan of 1 to 2 years. Also, both types should be used at a 2 to 2 ½ inch depth in a landscape bed and used more sparingly close to the trunk of each plant mulched.
Q: I need all information about providing florescent light for my many houseplants. We place some of the plants around our patio and porches during the summer but don’t have enough windows for all the houseplants during this time of year.
A: Maintaining potted plants under florescent lights inside requires that the lights provide the red and blue color spectrums that plants need. So, this part of indoor horticulture works best if a fluorescent light set-up is created over a bench or table where indoor plants can be maintained rather than having plants located here and there in rooms with bright florescent lights in the ceiling.
A major requirement is that florescent tubes and reflector should be hung by chains or other adjustable supports so they can be raised or lowered to maintain a distance of only 6 to 8 inches above the plants to receive the light.
The types of plants which may grow satisfactorily under florescent lights require a minimum of 15 to 20 watts per square foot. The 48-inch tubes of 40 watt capacity are very practical. Shorter tubes are less efficient, since they provide adequate light in only a small area. Reduced light is produced near the ends of tubes.
For a maximum light output, install tubes as close as 4 inches apart with 4 tubes per fixture. They should never be located more than 8 inches apart, with a minimum of two tubes per fixture.
Special grow-type florescent tubes are available. It is possible to get a good balance of light needed for photosynthesis by using 1 daylight florescent light tube along with 1 soft white or natural lamp in each fixture. Two of each type can be used in a 4-tube fixture.
To make your house plant florescent light system effective, the location should have a temperature close to 68 degrees Fahrenheit while the lights are on and a little cooler 60 degrees during darkness.
Also, put your florescent lights on timers so that they will turn on and off to provide 16 hours of light and 8 hours of darkness for each 24-hour period.
