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Garden Myths Busted: Sun+Water, Nursery Tags and Landscape Fabric

By Paul Rodman (paulgrowOctober 29, 2012
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Two horticultural professionals took some of the most popular garden myths into the university laboratory to prove or disprove the accuracy of these myths. Dr. Linda Chalker-Scott from Washington State University and Dr. Jeff Gilliam from the University of Minnesota tested these myths under controlled conditions to determine if they really work.

Gardening picture

The Myth
For years we've been told that if we water plants on a hot sunny day the sun reflecting through the water droplets will burn the foliage.

Image Image 

The Facts


We are constantly being warned in books, magazines, and various websites that if we water on a sunny day we will burn the leaves.  The premise behind this is the water drops that accumulate on the leaf surfaces act as tiny magnifying glasses, focusing the sun's energy into intense beams that burn leaves. We're told that since water conducts heat, wet leaf surfaces are more likely to burn than dry ones.  This is one of those myths that refuse to die. Although most of the university web sites dispel this myth, hundreds of other web sites keep the misinformation alive.

 If your plants are showing signs of water stress in the middle of the day, by all means you should water them!

Delaying irrigation until the evening (not a good time to water anyway, as this can encourage fungal diseases or the following morning could damage your plants and open them up to diseases.

There are many causes of leaf scorch, but irrigation with fresh water is certainly not one of them.

So remember:


Wet foliage is not susceptible to sunburn

Analyze site conditions to ensure optimal root and shoot health and prevent drought problems

Any time plants exhibit drought stress symptoms is the time to water them
Ideal watering time is in the early morning; watering during the day increases evaporative losses, and evening watering regimes can encourage establishment of some fungal diseases
 
Do not overuse fertilizers and pesticides, especially those containing sodium or other salts

If using recycled or gray water, consider running the water through a filtering system before applying it to plants.

The Myth

Using nursery tags is an accurate method to determine a plant's final size.

 Image

The Facts

Fall is the ideal time to plant trees and shrubs. Selection can be a tricky practice, especially when site conditions limit size of plantings. Small landscapes require small-scale plantings.

At the nursery, one can be overwhelmed by the variety of deciduous trees and conifers, and even within a species there may be several cultivars from which to choose.

Without any prior knowledge of these plants, gardeners resort to nursery tags to determine mature heights and widths. Armed with this information, one can select those trees and shrubs whose size is appropriate to the site. But does this approach really work?

Many factors determine the mature size of any tree or shrub. The most obvious on plant size is genetic makeup - you only have to look at cultivar names like ‘Midget' or ‘Giant Candles' to understand this component.

 Geographic location also plays a role in determining height. For instance, trees tend to grow taller in areas where temperatures are more moderate; trees in coastal areas are generally larger than these same species in more interior regions. Within a geographic area, local climate will further influence final size: rainfall and temperature can vary widely within a region. The microclimate of a site will influence tree size due to differences in environmental factors such as drainage, and soil type.

Competition for water, light, and nutrients, will affect not only growth rate but final height as well.

  • Nursery tags most likely contain species information relevant to that nursery's geographic location
  • Genetics, geography, climate, and plant competition will all influence the maximum height any specimen will obtain
  • To determine the most likely height range for a tree in your landscape, observe how that species performs elsewhere in your area
  • If no local landscape specimens exist for a particular plant, look to the internet for plant performance information from similar climates elsewhere in the world.

The Myth

Landscape fabric provides permanent weed control for landscapes

 Image

The Facts

Concern over the use of herbicides has caused landscape professionals and gardeners to look closely at non-chemical methods of weed control. Mulches are increasing in popularity as weed control measures and have a number of additional benefits, including water retention and soil protection. Mulches may be organic, inorganic, or synthetic.  Synthetic mulches, including geotextiles, are of interest to many consumers and professionals because they are perceived as nonbiodegradable, permanent solutions to weed control.

Developed for agricultural use, geotextiles have found their way into ornamental gardens as landscape fabrics. These fabrics, a vast improvement over the impermeable black plastics still (unfortunately) used for weed control, are woven in such a way that water and gas exchange can occur but light penetration is significantly reduced. Hence, they are effective in reducing weed seed germination in areas where soil disturbance would otherwise induce germination of weeds. Such fabrics have been so effective in reducing weeds in vegetable and ornamental crop production that they have been applied to more permanent landscape installations.

Like the dieter searching for a permanent weight loss pill, so we as gardeners continue to seek permanent weed control solutions. Unfortunately, there is no such permanent fix.

We must remain ever vigilant in our battle with weeds and cannot rely on a product to do this.  The fact is that weed control fabrics are not permanent and will decompose, especially when exposed to sunlight.

 For permanent landscapes, they are not a long term solution and in fact can hinder landscape plant health.

Some of these facts are listed below.

  • Any organic matter or soil on top of the fabrics will hasten their colonization by weeds; this precludes covering the fabric with anything but inoert mulch like pebbles. It also requires continual maintenance to keep the fabric free of debris.  Weeds will eventually grow on top of and through these fabrics, making their removal difficult.       
  • Geotextiles degrade in the landscape in as little as one year if unprotected from sunlight.
  • The aesthetic quality of landscape fabrics is minimal; it becomes worse as the materials begin to degrade.

Personally I had a situation where field bindweed grew some 25 feet under landscape fabric before emerging at the edge of the bed, seeking sunlight.

In closing, I expect some of you might disagree with some of these findings. However remember that this research was done in reputable university labs under controlled conditions. Each of us will draw our own conclusions.


  About Paul Rodman  
Paul RodmanPaul Rodman has been gardening for over 45 years. He is an Advanced Master Gardener, and American Rose Society Consulting Rosarian. He is President Emertius of the Western Wayne County Master Gardener Association in Wayne County, Michigan. He currently serves as the greenhouse chairman of this group. Rodman has amassed over 5500 volunteer hours in the Master Gardener program. Rodman is the garden columnist for The News Herald newspaper, in Southgate, Michigan. He has also written for the Organic Gardening.com web site. He is a certified Master Canner and has taught classes on Home Food Preserving for 7 years. He has lectured on various gardening topics throughout southeastern Michigan. His favorite pastime is teaching children about gardening. For the past several years he has conducted classes for second grade students teaching them about subjects ranging from vermi-composting to propagation.

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Discussion about this article:
SubjectTopic StarterRepliesViewsLast Post
Reason I quit using landscape fabric beachbum8 3 71 Aug 23, 2014 2:55 AM
AgreeNO to landscape cloth hsl2000 1 28 Jan 2, 2013 10:19 AM
It ain't necessarily so. dahlmarye 3 82 Nov 3, 2012 1:27 AM
Geotextiles cooked 1 71 Oct 30, 2012 2:03 PM
Yes marti001 2 61 Oct 29, 2012 1:20 PM
Thanks again! jazzy1okc 0 42 Oct 29, 2012 5:13 AM
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