Left photograph, a small kudzu sprout is covered by the top half of a 2-Liter PET plastic bottle. Right photograph, a kudzu sprout (left) was killed by the heat of the summer sun by covering it with the bottom half of a bottle (right). The effect is that of a mini-greenhouse gone bad, one that kills plants instead of nourishing them! September 2005.
This concept developed from a comment by Coalition volunteer Dr. Gill Newberry. She reasoned that if a 6 mil clear polyethylene sheet was doubled (folded over), then perhaps the effect might be for it to act like a lens. The additional thickness might intensify or magnify the Sun's radiant heat, producing additional heating.
Several two-liter clear empty polyester (PET) soda bottles, with labels removed, were cut in half and measured using vernier calipers to determine the thickness at the cut line. The reading of one ten thousandth of an inch (equivalent to 10 mil) was recorded. Six of these cut in half soda bottles (leave the cap secure on the top portion) acting as a hothouse were placed over six existing crowns. This is the Kudzu Coalition's first application and use of an ester plastic in any testing condition or situation to date.
The small amount of green sprout growth was selected due to the four inches diameter of the bottle. Limiting the crown growth size allowed space for several (two) thermometers to be placed inside two the hothouse soda bottles.
Six locations were flagged at the experimental test site, and will be monitored for results. It is worth noting the aggressive growing season in early September is somewhat diminished compared to the early spring vigorous growing season. Therefore the test results might not yield significant data to be useful. The progress will be observed and monitored. Perhaps one can confirm the lens effect of thicker polyester than the six-mil clear polyethylene sheeting.
Paul M. Savko
Subsequent work showed significant kudzu kill, but other heat treatments are more effective. The summary at the bottom of this page provides the pros and cons of this interesting treatment. Here is a June 2006 photograph that shows small kudzu plants covered by the top and bottom of a bottle.
One-Liter Hothouse: The Bottom Line