Austin Bonsai Society

July 2003

President's Message

by Glenda Konopka

June 21, 2003 - Hot, hot, hot! My Weatherbug warning system on my computer tells the temperature/humidity index outside is 113 - whew. Bill's presentation at the June Society meeting was just in time to help us all try and beat the heat for our bonsai. I've certainly got my fingers crossed about my pine trees.

Lot's of exciting things coming up: the July monthly meeting is our RSVP tropical saikei workshop; Joe tells me that 21 people signed up at the June meeting alone - this is going to be an awesome opportunity for us to get dirt under our fingernails, have fun with each other, and go home with a beautiful addition to our collections.If we don't finish that night, the Member's Study Group for July will be the opportunity for us to finish

Breeze' is coming up fast, so I hope you've all signed up for at least one of the great workshops being offered. Remember to give Pat Ware your raffle items and sign up to help out with the workshops - let's show everyone that the Austin Bonsai Society's members can help put on a great convention!

Last, but not least, be sure you've given Charlotte your volunteer hours from the May show.

Stay cool!

General Meeting Minutes

by Del De Los Santos

President Glenda Konopka called the Austin Bonsai Society general meeting to order at 7:35 P.M. with a minor introduction on the evening's program by Dr. Bill Cody on summer heat and its detriment to bonsai. Barbara Rodriguez and Carl Quisenberry provided refreshments. Visitors were:James Morgan Jr., his friend Eric, Bill Payton, past president and renewed member, Bill McConnell.

Under old business were announcements of the June 14th LSBF meeting at 1:00 P.M. at the garden center and a public note that the ABS board meetings are open for attendance. Also, the Shohin meeting is scheduled at Persimmon Hill Bonsai on June 21st. The membership workshop on soils is scheduled for June 25th, 7:30 P.M. at the garden center. An announcement was made regarding the July 9th workshop with Joe Waite of Bonsai Exotica on saikei, the club will purchase the plants, and members are to supply their own pots. Check with Joe Wait on details.  The meeting progressed with a most informative presentation by Bill Cody on the stress caused by summer heat on bonsai.

Board Meeting Minutes

by Del De Los Santos

Larry Gfeller called the ABS board meeting to order at 7:06 and announced that President Glenda Konopka would not be present. Board members in attendance were Treasurer Pat Ware, Secretary Del De Los Santos, Member at Large Carl Quisenberry. Visiting members were Chuck Ware, Elaine White, James Morgan, Jr. and Stephanie Quisenberry.

Treasurer, Pat Ware reported all expenses for the club show are not in yet. There could be possible charges from the garden center for extra hours, and the final cost from the dry cleaners to clean the tablecloths has yet to be determined. Discussion was held on how to protect the tablecloths for the next show from being readily soiled. We have yet to receive any claims from the vendors for items donated for the raffle. Pat reported $352 dollars were raised for the club from the raffle, $280 dollars from the vendors for table rentals for a total of $632 dollars; the current known cost of the club show was $1,910 of which $1,745 dollars of that cost was the new tablecloths. The show attracted 1,226 visitors in the two-day span.  Creating a listing for future reference as to where all show items are stored was discussed and it's creation was accepted by Del De Los Santos.

Elaine White addressed the board regarding publicity for the annual show and supplied much needed information and timelines with local new media for publicizing future shows. Larry Gfeller brought to the table news of rose society member, David Dixon who works as a reporter for News 8 Austin and the possibilities of inquiring of him the possibility of coverage for future events. Chuck suggested he be contacted about the Summer Breezes Symposium scheduled for July. Elaine White brought to attention that the final decision of what is covered in local media rest with station managers and editors.

The publicity officer for the garden center meets with KLRU on what appears to be a quarterly basis and scheduling notification in the past has not been advantageous. Chuck mentioned that no mater the amount of publicity we generate, we still suffer from the lack of parking at the garden center. Discussion was held on the bureaucratic greed of the city regarding its operations of public events at and near Zilker Park and the effects on all functions held at the garden center. Stephanie Quisenberry brought up a point of interest of advertising on the World Wide Web.  Larry Gfeller proposed aligning ourselves with other public service groups to increase public awareness of our presence. One example was possible demos at Generation Celebration, an event whose purpose is to bring grandparents together with grand children. Del De Los Santos brought up the fact that most ABS workers are already strapped and couldn't take on the other tasks. Chuck reiterated the need to  charge' (as in instill vigor/new life in) the membership to participate in club functions. Larry Gfeller proposed holding open bonsai classes/workshops to the public with a monetary charge for participation, there by exposing our existence and adding to club coffers at the same time.

Pat Ware mentioned the latest newsletter contained the error announcing the June workshop as scheduled for June 28, when in reality it is on June 25th.  Stephanie Quisenberry volunteered to call the membership with the correction.

Discussion was held and it was approved for Pat Ware to contact the garden center and change the time slot for the summer workshop with Marry Miller from noon to 11:00 A.M.  This change will give us a bit more time for workshop and still enjoy the company of our San Antonio guest at dinner and providing them enough time to drive home safely.  Larry Gfeller volunteered to develop a survey to poll members about workshop participation. There has been no word received from Mark Nolanders on his participation in a future workshop.

The meeting adjourned at 8:05 P.M., Pat Ware remained with new member James Morgan, Jr., who has volunteered to take over the newsletter.

Your Bonsai in Full Sun-Part 3

What Shade Fabric and Shading Technique is Best?

by J. R. (Bill) Cody

In a previous article we found that our bonsai in full sun are at risk of supraoptimal root zone temperatures.  Foster defines supraoptimal root zone temperature (SORTZ) as temperatures within the root ball of a plant between 89.6F and 104F.  Exposure of roots to temperatures within this range is detrimental to the general good health of the plant; exposure to temperatures above this range can be lethal to most plants.  Since the primary source of supraoptimal root zone temperatures is the influx of solar radiation striking the container's walls, the most efficient management would be to reduce this radiant energy from entering the growth medium.  One of the solutions suggested for this problem is to use a shade cloth above the bonsai and container.  Whitcomb tells us a 47% overhead shade is not detrimental to the growth of plants; however, no information was presented as to the protection of the root system beneath this degree of shading.  A second possible remedy recommended is to shade the root ball's container.  In bonsai culture there are alleged advantages for exposing the plants to full sun small leaves, short internodes, short needles.  To protect the root ball from detrimental supraoptimal root zone temperatures and still give the plant the benefit of exposure to full sun, what container shade cloth should we use to achieve these ends?  Does the shade cloth need to be suspended above the container and growth medium or may we just throw the cloth over the container in any old fashion?  In this study we set out to examine the efficacy of several easily obtainable fabrics of different shade densities, both synthetic fabrics and natural fiber fabrics, applied in two different ways to cover the bonsai container only.


We used five pairs of ceramic bonsai containers and three pairs of modified black plastic containers for a total of 16 containers.  Each container in a pair was similar in shape, depth, and volume as nearly as we could accomplish this from our in-house selection of ceramic containers.

Sixteen red liquid thermometers were calibrated using a mercury laboratory grade mercury thermometer.  Each thermometer was placed into a container at the same depth (1.5 inches) and two inches from the south wall of each container.

Temperature readings were recorded at two-hour intervals from 0600 to 1800 hours Central Standard Time for four days for each part of the study. There were zero days during this study in which the ambient temperature did NOT reach 100F.

In the first part of the study the pairs of containers were exposed to full sun without covers to determine if the temperatures recorded in each pair was comparable. In the second part of the study each type of fabric shade cloth was placed over a wooden frame that allowed the shade cloth to be suspended two inches above the level of the growth medium. The sides and ends of the shade cloth were long enough to drape over the frame to protect the sides of each container from the effects of any direct or reflected solar radiation but still allow for air circulation around the container.  A hole was made into each shade cloth so that a thermometer and its protective shield could be accommodated.  The containers were watered each night.  In the third part of the study the shade cloths were draped over each container without the frame.

Since growth medium characteristics affect the "thermal diffusivity" (rate of heat energy movement) of heat throughout the container, the drainable pore space and water holding capacity of the growth medium was determined by a method described earlier.  All were filled with the same growth medium, a 1:1::v:v mix of expanded shale and pine bark that would, when sieved, be retained on the one-eighth inch screen.  The mixture had an average drainable pore space of 56%, 56%, 52%, 45%, and 32% for 5", 4", 3", 2", and 1.5" deep containers respectively.  These values indicate a very coarse, porous growth medium.  This means that there are increased air spaces within the medium, which in turn will cause increased medium temperature gradients and lower temperatures in the growth medium itself.


Full sun, no cover:

This graph is the result of eight days of temperature measurements of the eight pairs of containers.  The temperatures recorded in each pair were averaged.  The large footprint, high profile ceramic container pairs (#1 & #2) became the hottest but had the slowest rate of heat gain and heat loss.  Of the container pairs of the low profile group (#3, #4, #5), the pair with the smallest volume (#4) was the hottest by a slender margin and cooled the fastest at the end of the day.  The large 21 inch by 1.5 inch oval container pair (#3) were consistently relatively cool, probably due to the combination of its shallow depth and large footprint which allowed for more rapid evaporation of growth medium moisture than the deeper containers as the internal temperatures rose. I have observed the same phenomenon in an identical 2.5-inch deep oval container containing a large cedar elm (unpublished data).  All of the black plastic commercial container pairs consistently absorbed more heat faster than the ceramic high profile containers, but lost their heat slightly faster than the ceramic group, the ceramic mass retaining heat more tenaciously than the thin black plastic.  Black plastic container #7 had the smallest volume relative to its high profile and was consistently the hottest of this group during the heat of the day.

Full sun, synthetic fabric covers with frames:

Container covers suspended upon a frame proved disappointing in their protection of their respective containers. The 100% shade cloth actually caused heat retention despite air circulation around the container.  The 80% covers were of no significant help either.  Only the 60% covers offered minimal protection, which was probably due to the relatively open weave fabric.

Full sun, synthetic fabric covers without frames:

Draping a shade cloth over your bonsai container is not recommended.  The more tightly woven the cover fabric the more intense the heat retention within the container, the internal temperatures being consistently higher than the temperatures in comparable containers in full sun, and the longer the higher temperatures persisted as the ambient temperature diminished.

Full sun, natural fiber fabric covers with frames:

I expected that the natural fiber fabrics tested on frames would be more effective in reducing the accumulation of heat within the containers.  And they did, but to a disappointing degree.  The canvas covers were similar in performance to the 60% synthetic covers during the heat of the day.  The thinner muslin did modify the length of time that the temperature within the containers was in the dangerous supra-optimal range compared to the synthetic fabrics and the canvas.

Full sun, natural fiber fabric covers without frames:

Natural fiber covers draped directly upon the containers also caused the retention of heat within the growth medium.  The heavier, more closely woven canvas caused heat retention in the same range as the 80% synthetic fabric; the muslin heat retention properties resembled that of the 60% shade fabric.  Despite being white, which should be advantageous to these natural fiber cloths, the closeness of the weave of both these candidates worked against their effectiveness by reducing the amount of ventilation and accompanying evaporation of moisture from within the growth medium in the container.  No reflective shade materials were tested because of probable damage to the leaves of the bonsai from reflected solar radiation.


Protecting your bonsai from supra-optimal root zone temperatures by covering their containers with the fabric covers to deflect the summer's direct and indirect solar radiation is not an option for bonsai enthusiasts, certainly not in the Sun Belt States.  There may be some other cover (e.g., the fiber glass in air-conditioner filters) that may turn out to be effective but I doubt it.  The reason for my doubt is that growth media in air layer polyethylene bags in full sun protected by a one an one-half inch thick styrofoam box covered with aluminum foil, barely limited growth medium maximum temperature to the lower limits of the supra-optimal root-zone temperature range. Obviously, this drastic approach is definitely impractical for bonsai on display. Most bonsai enthusiasts probably use growth media with a lower porosity than that used here and this would increase the temperature level in the root ball.  The inevitable decomposition of organic components and the accompanying compaction of growth media within our bonsai containers results in the same phenomenon, i.e., lower porosity and higher temperatures.  Bonsai with large foliage canopies, whose containers are also covered by fabric on a frame, may have some advantage.  Limiting our bonsai to exposure to morning sun only and/or heavy watering in the early afternoon are other options for the bonsai grower in the Sun Belt States.  However, considering the ever-changing current weather patterns, similar high temperatures may well become the norm for those bonsaiasts who live above the 40th parallel.

It is imperative that bonsai enthusiasts remember that summer-long exposure of bonsai root balls to supraoptimal temperature ranges has an accumulative effect on the health of our bonsai that may not be readily apparent during any single growing season.  However, several seasons of this sort of exposure may very well render your bonsai susceptible to a "normal' bonsai event stress (e.g., repotting), converting it into a lethal incident.