The Atlanta Orchid Society Bulletin
Affiliated with the American Orchid Society, the Orchid Digest Corporation and the Mid-America Orchid Congress 2001 Recipient of the American Orchid Society’s Distinguished Affiliated Societies Service Award Newsletter Editor: Danny Lentz Society Librarian: Elaine Jacobson
Volume 45: Number 7 www.altantaorchidsociety.org July 2004
JULY EVENTS The Meeting: 8:00 PM Monday, July 12, 2004, Atlanta Botanical Garden - Day Hall Mr. Mark Rose, Breckinridge Orchids
Mark Rose, the owner of Breckinridge Orchids in North Carolina, will present a wonderful slide show on species Paphiopedilums and will talk about their culture. Mark is well known for his work in Paphs and Phalaenopsis; and, since he grows in a climate similar to Atlanta, he should have a lot of useful information that Atlanta members can apply. He will be bringing plants for sale. You can order plants by phone at 336-656-7991. His website does not appear to be working (www.breckinridgeorchids.com). The cutoff date for preorders is July 8.
Inside This Issue Atlanta Orchid Society 2004 Officers…………………………………………..….…………… Page 2 Collector’s Item……Encyclia cordigera (H.B.K.) Dressler……Ron McHatton…..………... . Page 2 Events Out and About………………Dates for your Calendar…………...……….…….……… Page 3 Minutes of the June Meeting ………………..….…….…...……….………….…………….… Page 3 The June Exhibition Table (with notes by Ron McHatton)….………………………………..... Page 4 Recent AOS Awards from the Atlanta Judging Center…………………………………………. Page 7 American Cattleyas – book info……………………………………………………………….. Page 9 Second Quarter Exhibition Table Results, Notices……………………………………….……. Page 10 Understanding pH Management and Plant Nutrition part 4 : Substrates…….Bill Argo …….... After Page 10
All contents © Atlanta Orchid Society unless otherwise noted.
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THE ATLANTA COLLECTOR’S ITEM
ORCHID SOCIETY Officers Encyclia cordigera (H. B. K.) Dressler President En-SIK-lee-ah cord-eh-JEER-ah Evan Dessasau, III Tribe: Epidendreae 2431 Elkhorn Drive Decatur, GA 30034 Subtribe: Laeliinae 404-241-4819 Etymology: Greek enkyklein, to surround; in reference to the lip enclosing the column. Vice-President/Programs David Mellard As currently circumscribed, the genus Encyclia includes some 153 3409 Regalwoods Drive species ranging from southern Florida south into Mexico and down into Doraville, GA 30340 South America. The genus is characterized by the presence of 770-270-5758 pseudobulbs and, unlike Epidendrum from which the genus was
Secretary separated, the lip is free from the column for most or all of its length. Teresa Fuller The column lacks a column foot and there are four pollinia. 2090 Rockdale Circle Most species are epiphytes and, with the exception of those few Snellville GA 30078 requiring cool conditions, respond well when grown under intermediate 770-972-2634 conditions and light levels at, or slightly exceeding, those provided for
Treasurer Cattleya. In many instances if humid conditions can be provided the Scott Smith plants respond well to mounting. 481 W. Ontario Ave. Encyclia cordigera is arguably one of the most readily recognized and Atlanta, GA 30310 sought-after species. It grows from Mexico south to Colombia and 404-752-6432 Venezuela. This species has been known under the names Epidendrum Immediate Past President atropurpureum, and Encyclia atropupurea although Encyclia cordigera Linda Miller predates both of these and is the name that should be used. The plants 135 Pheasant Drive occur in at least two distinct color forms. The one most commonly Marietta, GA 30067 encountered in cultivation, Encyclia cordigera var. rosea has red-brown 770-953-2853 sepals and petals and a rich, dark rose-red lip. Several generations of line Directors breeding have essentially removed the characteristic folding of the lip along its center-line and in highly selected clones, the flowers can have Term Expiring 2004 exceptionally rich color. While this varietal form is most often Frank Decaminada encountered in cultivation it is not the most common in the wild. The (770) 992-8309 Andrew Dott typical wild color form has brown to red-brown sepals and petals and the 404-256-7858 lip is white with a red to purple-violet blotch at the base of the disc. In addition albinistic clones are occasionally seen, which are typically fewer Term Expiring 2005 flowered with green sepals and petals, a white lip, and a central green Mark Reinke blotch at the base of the lip midlobe. 404-622-4872 Jeff Whitfield 706-675-3583
Term Expiring 2006 Richard Ackerman 770-978-6109 Fred Missbach 404-237-1694
Refreshments
Photo courtesy of Danny Lentz Photo courtesy of Ron McHatton Page 3 www.atlantaorchidsociety.org July 2004
Events Out and About MINUTES OF THE JUNE MEETING
July The meeting was opened by president Evan D. Dessasau,III. Saturday, 7/10. American Orchid Society The May minutes were approved. monthly judging, Atlanta Center, 2 pm, ABG basement workshop. If entering plants, please Fred Missbach reminded everyone of the upcoming annual arrive before 1:30 pm to allow time for research Auction. We were reminded to bring a dish and about the and paperwork. time of the event. He also gave directions to the Lodge and reminded the membership of directions in the Newsletter. Monday, 7/12. Atlanta Orchid Society monthly meeting, ABG, Day Hall. Mark Rose from Fred Missbach, being the Orchid Digest Corp. rep., also Breckinridge Orchids will talk about species spoke to the membership about the Orchid Digest Magazine. Paphs. David Mellard asked the membership to check the final draft August of the roster for corrections. Monday, 8/9. Atlanta Orchid Society monthly David also reminded the membership about greengrowers meeting, ABG, Day Hall. Norman of Norman’s coming up at Ben Lyda's June 26. Orchids will speak about harlequin Phalaenopsis. Plant orders will be accepted An announcement to visitors and latecomers was made until July 30 by calling 1-888-4Orchids. You informing them that our June program was touring the can also visit his website at www.orchids.com to greenhouses. see orchid lists. Preorders get a 10% discount plus free shipping. He will bring plants to sell. Refreshments were served and the ribbon judging was announced by Mark Reinke. Saturday, 8/14. American Orchid Society monthly judging, Atlanta Center, 2 pm, ABG The Raffle was held. basement workshop. If entering plants, please arrive before 1:30 pm to allow time for research With no further business the meeting was adjourned. and paperwork. Respectfully Submitted, E-van D. Dessasau,III
JOIN THE ORCHID DIGEST CORPORATION ORCHID DIGEST DUES INCREASE
Don’t let the name fool you, the Orchid Digest is a non- Orchid Digest dues are being increased due to ever profit membership-based organization dedicated to orchids. Designed to appeal to the mid-range to rising publication and shipping costs. Effective 9/1/04, advanced grower nothing beats the Orchid Digest. For a single year will be $32 and two years will be $60. just $28/year you get 4 issues of full-color, in-depth Anyone who renews prior to the 9/1 cutoff date can articles about orchids. The magazine is large format and still renew at the old rates ($28/$54) regardless of when the fourth issue of the year is always an extra-special issue devoted to a single genus. their subscription ends.
For membership application forms contact Fred Missbach. Page 4 www.atlantaorchidsociety.org July 2004
JUNE 2004 EXHIBITION TABLE AWARDS with notes by Ron McHatton
CLASS 1: CATTLEYA ALLIANCE Blue Laelia tenebrosa Hallberg Red Schombocattleya Margaret Brown Collier/Reinke White Laelia tenebrosa Hansen White Brassolaelia Golden Glory Collier/Reinke
Laelia tenebrosa : In addition to the dark bronze or coppery flower typical of this species, Laelia Laelia tenebrosa tenebrosa also occurs in at least two other rare color varieties. The clone ‘Walton Grange’ lacks the usual bronze pigmentation resulting in a flower with intense citron-yellow sepals and petals and a white lip veined with reddish tones. There are also at least two clones completely lacking in red or purple pigmentation. The flowers of these clones have yellow sepals and petals and a completely white lip. While this species has a somewhat open form, it has been used extensively in hybridizing because of its ability to intensify pigmentation in its offspring. When mated with C. dowiana or C. aurea, the resulting flowers are an intense, glowing, dark magenta to red. One other interesting observation in breeding is that the typical dark color is dominant in crosses between the normal and yellow clones (the white ribbon winner is from such a cross).
CLASS 2: CYMBIDIUM Blue Grammatophyllum marlae ‘Lahing Kayumanggi’ Rinn
Grammatophyllum martae : The Philippines is the center of distribution of this genus with 8 or 9 of the 11 species found throughout the island archipelago. All species in the genus respond best to warm, bright conditions. This Philippine species is found in the Negros Occidental region and was described by Quisumbing but apparently never validly published. As with all Grammatophyllum species, the plants are politely referred to as “robust”. Another trait shared with the other species in the genus is the common occurrence of deformed flowers at the bottom Gramatophyllium of the raceme. This deformity is most often the absence of a lip on the lowermost 1-3 flowers Marlae although partial double flowers are also encountered.
CLASS 3: DENDROBIUM Blue Den. farmeri Hallberg Red Den. Haleahi Nymph Lentz/Morgan White Den. secundum Hallberg
Dendrobium farmeri : This species belongs to the section Callista, a group of about 10 species widespread throughout mainland Southeast Asia. All species grow at moderate to high altitudes in areas with a sharply pronounced dry season. While the species are easy to grow and will adapt Den. farmeri reasonably well to warm conditions, flowering will be poor to absent without a prolonged cool, dry rest. Dendrobium farmeri will easily handle low temperatures down to around 40F and will even survive colder conditions if they are kept dry. Other species is the section are Dendrobium chrystoxum, densiflorum, thyrsiflorum, sulcatum, palpebrae (a very similar species lacking the violet tinge of D. farmeri) and D. lindleyi (syn. D. aggregatum). Page 5 www.atlantaorchidsociety.org July 2004
CLASS 4: EPIDENDRUM Blue Epidendrum Pacific Sunsplash Brinton/Park Red Epicattleya Middleburg ‘Mas’ AM/AOS Collier/Reinke White Encyclia tampensis ‘Mendenhall’ Lyda
Epidendrum Pacific Sunsplash : This plant was entered as an unregistered grex (Epi. Eagle Valley x Epi. Sun Valley). We are beginning to see more and more of these reed-stemmed Epis bred in Japan to reduce the cane height in mature plants. Any of you who have tried to grow Epidendrum Pacific plants of Epi. Ibaguense (syn. Epi. radicans) know that these plants can reach 6-8 feet tall. In Sunsplash addition to their height, the canes are very slender, brittle and have a tendency to produce new growths at some distance from the base of the plant making them difficult to maintain. The newer, smaller growing hybrids are much more manageable and will mature at a height around 3 feet (not counting the inflorescence). In addition, they are much less likely to produce new growth along the cane making them more tailored than their older cousins.
CLASS 5: ONCIDIUM ALLIANCE Blue Odontoglossum cirrhosum Rinn Red Onc. (Golden Sunset x Stunner) Hansen White Miltonidium Summer Fantasy ‘Betty’ Dampog
Odontoglossum cirrhosum : This species is found in southwestern Colombia and western Ecuador and into Peru at altitudes ranging from 1600 to 2200 meter (about 7000 feet). This high elevation makes them not the easiest subjects to grow and flower well. Congratulations to the grower! Robust clones of this species can have flowers approaching 10cm (4 inches) Odontoglossum and carry up to 50 or more flowers per inflorescence. cirrhosum
CLASS 6: CYPRIPEDIUM ALLIANCE Blue Paph St. Swithin Hallberg Red Paph. Madame Martinet Brinton/Park White Phrag. Grande Brinton/Park
Paphiopedilum St. Swithin : Primary hybrids of Paph. rothschildianum are terrific plants. As a general rule, they are smaller, more easily flowered plants and, with the exception of those involving single-flowered species, have high flower count making them a great bargin for the space they consume. Paphiopedilum St. Swithin can be expected to produce 4-5 flowers/inflorescence on a mature plant. This particular plant appears to be of rather light color and great form. The light color is not a fault, just the result of a light color form of Paph. St. Swithin Paph. philippinense as the parent.
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CLASS 7: PHALAENOPSIS ALLIANCE Blue Phal. Brother Lawrence Rinn Red Phal. Brecko Garnet Rinn White Dtps. Pretty Nice 'Purple Magic' Brinton/Park
Phalaenopsis Brother Lawrence : This cross, Phal. (Taipei Gold x Deventeriana) was registered in 1995. The original cross was of high quality as is the remake we are starting to Phal. Brother Lawrence see appear recently. The flowers are easily recognized by their bright yellow sepals and petals with a pronounced white halo surrounding the column. The rust colored markings vary in number and intensity from clone to clone although none are as heavily marked as the Phal. Deventeriana parent, the result of the influence of the soft yellow Phal. Taipei Gold. The flowers are quite long-lasting and inflorescences typically are branched in well-established plants. Substance and texture of the flowers is much improved over the Taipei Gold parent, traits inherited from Phal. Deventeriana as is the white halo.
CLASS 8: VANDACEOUS ALLIANCE Blue Ascocenda ampullaceum var. alba ‘Fuch’s Snow’ CHM/AOS Gilmore Red Paraphalaenopsis (Boediardjo x serpentilingua) Rinn White Paravanda Martin Motes Hallberg
Paravanda Martin Motes : This plant was entered as an unregistered grex involving Paraphalaenopsis laycockii x Vanda denisoniana. Only recently has the RHS begun recognizing hybrids of Paraphalaenopsis as such. Prior to this change, these plants were considered to be
Ascocenda Phalaenopsis and such a cross would have been registered under Vandaenopsis. The yellow color ampullaceum var. alba of Vanda densoniana is largely suppressed by the Paraphalaenopsis parent resulting in typically ‘Fuch’s Snow’ cream colored flowers. As a balance, the longer, more loosely arranged inflorescence of the former is typically dominant. There are two clones of this hybrid with AOS awards and in both cases the flowers were described as carried well above the foliage.
CLASS 9: MISCELLANEOUS OTHER GENERA Blue Bulb. carunculatum ‘Magnifico’ AM/AOS Brinton/Park Red Bulb. lobbii ‘Kathy’s Gold’ Hallberg White Stanhopea oculata Hallberg
Bulbophyllum carunculatum ‘Magnifico’, AM/AOS : This Philippine species was described by Drs. Garay, Hamer, and Siegerist in Lindleyana in 1995. The species epithet refers to the warty surface of the lip. One word of advice; don’t touch that lip. It’s the osmophore (scent producing structure) and if you touch it, your finger will have that foul scent for some time. In addition to the Philippines, the species is also found in Sulawesi. Clones from the Philippines are characteristically solid yellow to chartreuse while some clones from Sulawesi have striped petals. This species responds to typically Bulbophyllum conditions; warm and moist throughout the year with moderate light and high humidity. Bulb. carunculatum ‘Magnifico’ Page 7 www.atlantaorchidsociety.org July 2004
RECENT ACTIVITIES OF THE ATLANTA JUDGING CENTER The following awards were granted at the May session of the AOS Atlanta Judging Center and at the May MAOC Speaker’s Forum in Atlanta. They are provisional awards pending official publication in the Awards Quarterly. Certificates of Horticultural Merit and Certificates of Botanical Recognition are also provisional pending identification by an AOS certified taxonomist prior to publication of the award.
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Dracula inequalis ‘Atrice Hughey’ C. walkeriana var. alba ‘Barney’ CCM 81 pts AM 83 pts (provisional pending id) Exhibitor: Mountain View Orchids Exhibitor: Barney & Aileen Garrison
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Bulb. A-doribil Ring ‘Anna Mae Rhodes’ Bulb. spiesii ‘Stinky Winkie’ AM 80 pts AM 85 pts, CCM 86 pts Exhibitor: Dan & Madeline Nelson Exhibitor: Fred Missbach
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Photo © Judy Cook Photo © Judy Cook Photo © Judy Cook
Paph. Robinianum ‘Ramona Lee’ Phrag. Paul Eugene Conroy Phrag. Ashley Wilkes ‘Charleston’ AM 82 pts ‘Kathy Ann’ AM 84 pts Exhibitor: Fred Missbach AM 83 pts Exhibitor: H.P. Norton Exhibitor: Dennis Billings
Photo © Judy Cook Photo © Judy Cook Photo © Judy Cook
Bulb. A-doribil Surprise Dactylorhiza purpurella C. gaskelliana var. alba ‘Stiff Wind’ ‘Mello Purple’ ‘Ramona Lee’ AM 83 pts CHM 83 pts HCC 78 pts Exhibitor: Robb Rinn Exhibitor: David Mellard Exhibitor: Fred Missbach Page 9 www.atlantaorchidsociety.org July 2004
AMERICAN CATTLEYAS Species and Outstanding Clones That Define American Hybridizing By Professor Courtney T. Hackney University of North Carolina – Wilmington
Coming Summer 2004
A new publication that chronicles the development of all major lines of Cattleya hybrids in the United States will be available this summer. Based on extensive interviews of prominent American hybridizers and commercial growers, scientific articles, the orchid trade magazines, and the author’s 30-year experience growing orchids, this book is oriented towards those with an interest in the “Queen of Orchids”. Written for the hobbyist in an easy to read style are chapters on species that form the basis of modern hybrids, hybridizing strategies, inheritance in Cattleyas, culture, exhibiting and judging different hybrid lines, and on the many nurseries and individuals that contributed to the rich history of this group of orchids in America. Most of the book’s narrative follows the development of the major hybrid lines in the Cattleya Alliance, from foundation species to prominent clones of hybrids responsible for today’s award winners, all illustrated in a 76 page color gallery containing over 300 photographs. Some of these photographs are over 50 years old, while others show the modern culmination of hybrid lines.
To limit the cost of this extensive publication, this volume is being offered as a Limited Edition based on preorders. Copies will not be available from the publisher. To reserve a copy you must submit a preorder form. Send no money. Orchid clubs are urged to pool their orders and save on shipping costs. Commercial orders will also be accepted. At the time of publication those that have submitted a preorder form will receive an order form along with payment information. Preorder forms may be submitted by mail to C. T. Hackney, 7007 Northbend Rd, Wilmington, NC 28411 or via email to [email protected]. The Cape Fear Orchid Society (capefearorchid.org/cat.html) has several pages of the book (including color photos) on its web site for viewing as well as a Preorder Form.
American Cattleyas: Species and Clones That Define American Hybridizing by Courtney T. Hackney, 2004, Falcon Books, 142 pp text, 76 pp color photographs, 4 tables, 4 figures, 4 stand-alone boxes, and extensive bibliography. Preorder price $39-41 plus nominal shipping and handling. Hardcover.
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Second Quarter Exhibition Table Results
Quarter Name April May June Total Brinton/Park 10 24 15 49
Collier/Reinke 16 22 7 45
Rinn 11 21 32 Lyda 21 8 1 30 Lentz/Morgan 16 10 3 29
Mellard/Marino 5 18 23 Hallberg 21 21 Gilmore 9 5 14 Dampog 9 1 10 Ackerman 7 7 Hansen 3 4 7 Grzesik 6 6
From Norman's Orchids Whitfield 5 1 6 Coombs 3 0 3 ...... any pre-order by Atlanta Society Members Brannon 1 1 2 need to be received by our nursery by July 30 , Frank 1 1 2004. This will allow us time to prepare for the Herzfeld 1 1 order. Members can call our toll free number 1 Potter 1 1 888 4 Orchid to place the order and mention it's for Norman to bring to the meeting that night (August 9th).
Here is the link to take a visual tour of our nursery. Please share the To submit material for the newsletter, or links with the members: to sign up for the email version of the http://www.orchids/com/EventImages/2004Sprin newsletter, please contact Danny Lentz: g/index.htm [email protected]
MAIL TO: Danny Lentz 1045 Wordsworth Dr. Roswell, GA 30075 JOIN THE AMERICAN ORCHID SOCIETY For $46.50/year, you reap the following benefits: The deadline for submissions is the 20th. • 12 issues of Orchids, the Society’s monthly full color magazine chock full of insightful articles and tempting ads for plants and supplies. Please visit our web site at • 10% off on purchases from the Society’s Bookstore and Orchid Emporium.Reduced or http://www.atlantaorchidsociety.org . If free admission to participating botanical you have suggestions or, better yet, gardens. material to contribute to the site, contact For a limited time, if you join for two years ($84) you will Tom Kaschak at 678-474-9001 also get a $30 gift certificate (good on an order of $100 or more) at any one of 13 commercial growers who advertise Remember that Tom is a volunteer also and in Orchids. JOIN TODAY. For information, contact Evan Dessasau. will certainly appreciate the help. Understanding pH management and plant nutrition Part 4: Substrates
Bill Argo, Ph.D. Blackmore Company, Tel: 800-874-8660, Int’l 734-483-8661, E-mail: [email protected] Originally printed in 2004 in the Journal of the International Phalaenopsis Alliance, Vol. 13 (3).
A wide range of substrates are available on the space, 0.96 liters of water, and 0.24 liters of solid. In market to grow orchids, or many other plants. Some general, substrates used for propagation tend to be very people are using substrates manufactured by large fine (lots of micropores) and so hold more water (on a companies for the production of container grown crops relative basis) at the expense of air space when other than orchids. Other people are using substrates compared to the “ideal” substrate. Coarse substrates manufactured primarily for growing orchids. Still have lots of macropores and so have greater air space at others are blending their own substrates from individual the expense of water. components. Container height also affects the ratio of The choice of substrates will affect the air:water held in a substrate after an irrigation. In effectiveness of your fertilizer program. Substrates can general, the shorter the height of the container, the differ substantially in both their physical properties and greater the percentage of pore space that is filled with chemical properties. In part 4 or this series, we will water and the lower the air space. For example, after a discuss key aspects of physical and chemical properties, thorough watering, the average air and water porosity of and also leaching, and how these factors affect plant five different commercially available root media in a 6 nutrition. inch (15 cm) tall pot was 19% (air) and 64% (water), in a 4 inch (10 cm) tall pot was 13% (air) and 70% (water), in Physical properties a 3 inch (8 cm) tall cell bedding flat was 7% (air) and Physical properties deal with the ratio of 76% (water), and a 1 inch (2.5 cm) tall plug flat was 2% air:water:solid in a substrate. Container substrates (air) and 82% (water), respectively. The percentage of should be thought of as a sponge. A sponge is made up solid material in the root media remained constant in the of the material used to make the sponge (solid space) different container sizes. It was the ratio of air space to and holes (pore spaces). If a material has a high bulk water space that changed with the different container density (high weight per unit volume), then a sponge of heights. This is one reason why it is easier to overwater this material would have a lot of solid space with little a small pot than it is a large pot because the air space in pore space. Examples of high bulk density materials the small pot is lower than that found in the larger pot are sand, clays, or field soils. In comparison, a sponge after an irrigation. made from materials that have a low bulk density (low Finally, the ability of a substrate to absorb weight per unit volume) would have little solid space water will affect physical properties. Ideal physical but lots of pore spaces. Examples of low bulk density properties are measured in a laboratory by allowing the materials are peat, coir, bark, vermiculite, things substrate to remain submersed in water for 24 hours commonly found in container substrates. before allowing it to drain (the difference between the Pore space can be filled with either air or water. saturated weight and drained weight (in grams) is a The ratio of air to water in a given substrate will depend measure of air porosity). In comparison, a typically on size and distribution of the pores. During an irrigation may last for only 30 seconds or less. That irrigation, small pores (called micropores) tend to fill means that under a typical irrigation, most substrates completely with water, while large pores (called will not rewet to maximum saturation, resulting in more macropores) tend to drain, which allows air to get back air space and less water-holding capacity than is into the substrate. It has been said that after an measured in a laboratory test. irrigation, the ideal container substrate would have 25% Another problem with organic substrates like of its volume taken up with pores filled with air, 60% of peat and (especially) bark, is that they become water- its volume taken up with pores filled with water, and the repellent if allowed to dry too much. Commercial remaining 15% taken up with solids. substrates will often contain a wetting agent or To put numbers on these values, an “average” 6 surfactant that aids in rewetting (increases water inch (15-cm) azalea pot has a volume of about 1.6 liters. absorption). For long-term greenhouse crops, like The volume of air, water, and solid occupied by the hanging baskets, it is often recommended to reapply a “ideal” substrate in this pot would be 0.4 liters of air surfactant to the substrate every month or two because Not for publication or reproduction without the authors consent. Pg. 1 the surfactant will degrade over time, resulting in a base found in 5 pounds of limestone. If you are only decrease in water absorption (more air space). If you watering once a week, then it will take 40 weeks to want to apply a wetting agent to your orchids, choose bring the substrate pH up to an acceptable level. If you one that is designed specifically for organic substrates are using a pure water source without any alkalinity, and cut the rates found on the label in half to reduce the then you may never get the pH up to an acceptable potential for phytotoxicity. level. The presence of limestone in the substrate has also been shown to increase the buffering capacity Chemical properties when using acidic fertilizer solutions. Chemical properties generally refer to a substrates Finally, substrate degradation will affect ability to buffer the water held in the substrate against nutrition and pH management. Degradation is the changes in either pH or nutrition. The term most often breakdown of the substrate, similar to composting. Of used to describe chemical properties is cation exchange all the materials commonly found in container capacity or CEC. CEC refers to the ability of substrate substrates, bark is the least stable, and therefore the particles (such as peat) to absorb and release positively most susceptible to degradation. The problem with charged cations like potassium, ammonium, calcium, or degradation is that it not only absorbs all the nitrogen magnesium, thus buffering the substrate against sudden present (causing nitrogen starvation), but the process changes in pH or nutrient levels. also tends to be very acidic. Hardwood barks tend to be An example of how CEC affects pH and nutrient the most stable. Softwood barks usually require some management occurs when a fertilizer solution is applied composting to make them stable. If a bark (any bark) to a substrate. A fertilizer high in ammoniacal-nitrogen contains any wood, then it is unacceptable for use in produces acid (H+). The acid is absorbed by the container substrates because the wood will cause will substrate and a different cation, usually calcium, is cause rapid degradation and nitrogen absorption. released. Conversely, a fertilizer high in nitrate- nitrogen (usually calcium nitrate based) produces base Leaching (either OH- or HCO3-). The base causes an acid (H+) Leaching is the application of water or fertilizer bound by the substrate to be released, which will then solution beyond what can be held by the substrate. react with the base to produce water (H2O) or CO2. In Applying extra water is recommended to thoroughly both cases, the net result is that the pH and calcium wet the substrate, and to remove excess salts from the concentrations remain stable. Substrates that have high substrate. The leaching fraction is the volume of water CEC (more buffered) can resist a change in pH for long that drains from the substrate relative to the volume of periods of time, whereas pH can change very rapidly in water applied. For example, if you apply 15 fluid substrates that have low CEC (less buffered). ounces (0.44 liters) of water, and 3 fluid ounces (0.08 CEC can play an important role in pH buffering liters) comes out of the bottom of the pot then 3 divided when a field soil is added to a container substrate. by 15, then times 100 equals a 20% leaching fraction. CEC-based pH and nutrient buffering does occur with In other words, 20% of the water applied to the plant field soils because the substrate has a high bulk density came out of the bottom of the pot. (weight). In contrast to field soils, research has shown It is generally taught that you should have that the CEC of peat, coir, or bark-based substrates has between a 10% and 20% leaching fraction with every little effect on resisting change in pH or in supplying watering. However, research has shown that leaching is nutrients. not necessary for long periods of time if you have a This does not mean that the substrate plays no good water source (RO or rain water is ideal) and the role in pH or nutritional management. Peat tends to be fertilizer you use does not contain any harmful salts like very acidic. Limestone is commonly added to peat- sodium or chloride. There are reasons to leach pots, based substrates to neutralize the acidity and bring the usually because the fertilizer concentration that is pH up to an acceptable level for plant growth. The applied to the crop is too high for the growth rate, or the amount of acidity found in most acidic peats will not be water quality is poor, and unused salts (like calcium, neutralized very quickly by bases found in irrigation magnesium, or sodium) build up in the substrate. In water. Using the example given in Part 2 of this series, general, whether or not you leach should be based on a limestone incorporation rate of 5 pounds per cubic soil test information showing salt levels actually yard will supply approximately 100 meq of limestone building up in the substrate, rather than because per 6 inch (15-cm) pot. Applying 16 fluid ounces (0.5 somebody tells you too. liters) of water containing 250 ppm alkalinity to that 6 Leaching rates also affect the optimal fertilizer inch pot will supply about 2.5 meq of lime. That means concentration for your crop. Research has shown that that 40 irrigations are required to equal the amount of the same nutrient levels could be maintained in a peat-
Not for publication or reproduction without the authors consent. Pg. 2 based substrate if a solution containing 400 ppm applied to the crop. The point is that by measuring the nitrogen were applied with 50% leaching or a solution pH and EC of the substrate, they can make sure that a containing 100 ppm nitrogen were applied with 0% particular fertilizer solution is doing what they think it leaching. This research also showed that applying a is doing, and make changes if things are going wrong, solution containing 400 ppm nitrogen with 0% leaching usually long before there are noticeable problems with rapidly lead to salts building up in the substrate to the plant. unacceptable levels, while applying a solution Even though there is not a lot of specific containing 100 ppm nitrogen with 50% leaching lead to knowledge about acceptable ranges for substrate pH and nutrient deficiencies because there wasn’t enough of the EC with orchids, it is probable that they are similar to fertilizer remaining in the pot because of the excess almost all other crops and so will grow best in a leaching. substrate pH around 6.0. Because they appear to be somewhat salt sensitive, they will also grow best with a Applying fertilizer to a substrate substrate EC slightly lower than the optimal level When you apply fertilizer to a substrate, which recommended for most crops. If testing with a pour- is more important, the concentration of the fertilizer thru method, then the desired substrate EC would be solution, or the volume that you apply? In fact, both are between 1 and 2 mS/cm. important because as a plant grows, it adds mass, and a portion of this mass is made up of fertilizer nutrients. It has been shown in a number of experiments that it is the amount of fertilizer applied to a crop that affects crop quality, not simply the fertilizer concentration. To calculate the amount of fertilizer applied, you need to know both the fertilizer concentration and the volume applied. For example, applying 1 liter (about 1 quart) of a fertilizer solution containing 100 ppm (100 mg nitrogen/liter) will supply 100 mg of nitrogen. If only 0.5 liters (about 1 pint) were applied of the same fertilizer solution, then only 50 mg of nitrogen would be applied. This can be especially important when you are only applying fertilizer on a weekly basis. If the amount of fertilizer solution being absorbed into the substrate decreases for any reason (decreased water- holding capacity), they you could end up starving your plants.
How do commercial growers manage pH and nutrient levels Commercial growers have learned that a single fertilizer concentration may or may not work depending on a number of factors including leaching, growth rates, light levels, irrigation frequency, etc. Instead, many growers will manage the pH or nutrient level within the substrate itself. This requires that the grower tests the pH, electrical conductivity, and perhaps even the specific nutrient levels contained in the substrate on a regular basis (see Sidebar). These measured values can be used to make adjustments to the fertilizer solution. For example, if the substrate pH is too high, then a grower might switch to a fertilizer containing more ammoniacal nitrogen, or they may lower the alkalinity of the water. If the EC of the substrate is too high, the grower may increase the leaching rate, or decrease the concentration of fertilizer
Not for publication or reproduction without the authors consent. Pg. 3 Monitoring Media pH and Nutrient Levels For successful pH and nutritional management of container grown crops, the goal is to keep the pH and nutritional levels within an acceptable range and to spot problem trends early on. This is a far better strategy than blindly applying fertilizer and hoping everything is OK, or having to take dramatic steps to rescue stressed plants. Using reliable meters, you can measure pH (which affects the availability of nutrients) and electrical conductivity or EC (the overall concentration of fertilizer salts) in substrates. Other advantages or in-house testing are that the tests are inexpensive and the results to be obtained quickly, typically in less than 1or 2 hours. How often do you test? Typically commercial growers will test substrate pH and EC every 2 to 3 weeks. That does not mean they test every pot or every crop every two or three weeks. Instead, they may do some random sampling to make sure everything is pH and EC are within acceptable levels, or they may test a few know problem crops and then assume that if their pH and EC are within acceptable levels, then other, less sensitive crops are not having problems. There are a number of different testing methods commonly used for measuring the pH and EC in container substrates. 1:2 method Saturated media extract method. Pour-thru method Squeeze Method. For additional information on the saturated media extract For more information on the Pour-thru method, see the web method, see Michigan State University extension bulletin site www.pourthruinfo.com. E-1736 “Greenhouse growth media: Testing and nutrition guidelines” by D. Warncke and D. Krauskopf. Step 1. Collect a small amount of substrate from the Step 1. Collect a small amount of substrate from the Step 1. Irrigate the crop one hour before testing, Step 1. Irrigate the crop one hour before testing, bottom 2/3rd of the pot. For very small plants, like bottom 2/3rd of the pot. For very small plants, like making sure the substrate is thoroughly wet. making sure the substrate is thoroughly wet. those being grown in plug trays or bedding flats, those being grown in plug trays or bedding flats, use Allow the pots to drain for 30-60 minutes. Allow the pots to drain for 30-60 minutes. use the whole cell as a sample. Take samples from the whole cell as a sample. Take samples from 5 to 5 to 10 or more plants distributed in the group of 10 or more plants distributed in the group of plants Step 2. Once drainage has stopped, place the pot to Step 2. Collect a small amount of substrate from the plants to be sampled. When a sufficient amount of to be sampled. When a sufficient amount of be sampled into a plastic saucer and pour onto the bottom 2/3rd of the pot. For very small plants, like substrate is collected, thoroughly mix the sample to substrate is collected, thoroughly mix the sample to surface enough distilled water to get about 2 oz. those being grown in plug trays or bedding flats, ensure uniformity. ensure uniformity. (50 ml) to come out of the bottom of the pot. use the whole cell as a sample. Take samples from 5 to 10 or more plants distributed in the group of Step 2. Measure out a known volume of substrate in a Step 2. About 4 to 8 oz (150 to 300 ml) of fresh Step 3. Measure pH and EC directly in the leachate plants to be sampled. When a sufficient amount of beaker or cup [usually 2-4 oz. (50 to 100 ml)]. The substrate is placed in a cup. Distilled water is substrate is collected, thoroughly mix the sample to beaker should be firmly filled with the substrate so slowly added while the sample is constantly ensure uniformity. that it is slightly more compressed than when it was stirred with a spatula or knife until it has reached in the pot. Place 2 equal volume of distilled water a consistent moisture level. This is determined to Step 3. Squeeze the solution from the media. For a into cup. Allow the solution to equilibrate (30-60 be when the sample behaves like a paste, the cleaner sample, media can be squeezed through minutes) before measuring pH and EC. surface glistens with water, but there is no free a paper towel or coffee filter. The volume of water on the surface of the sample. The solution solution needed will depend on the type of pH or is allowed to equilibrate for 60 minutes EC meter used for testing.
Step 3. Measure pH and EC directly in the slurry. Step 3. Measure pH directly in the slurry. Step 4. Measure the pH and EC in the extracted solution Step 4. Extract the solution from the media by squeezing slurry through paper towel or a coffee filter. Measure EC in extracted solution.
In general, there is no one “best” method for measuring substrate-pH or EC in the greenhouse. However, with orchids, especially with specimen plants, the pour-thru method may work best because it will not damage roots. Other reasons for deciding on which method to use in your greenhouse include any experience that you have with a particular method as well as how much help and advice you can get from other people that are close by such as other growers, extension agents, universities, or soil testing laboratories. Whichever soil testing method you choose, consistency is the key to making that method work. Consistency starts with having a single, trained person taking the test. Other tips include: 1) Choose one soil testing method and stick with it. Different methods can give different results. 2) When removing substrate from the pot, take the sample from the bottom 2/3rd of the pot. The bottom 2/3rd is typically were the roots are in the pot and sampling in this way avoids fertilizer salts that can accumulate at the substrate surface with all irrigation methods (not just subirrigation). 3) Try to take media samples roughly the same time before or after an irrigation. This is especially important with the squeeze method. 4) Choose a reliable pH and EC meter and calibrate it regularly. Calibrating solution has an expiration day and should be discarded when that date is reached. Not for publication or reproduction without the authors consent. Pg. 4 Table 1. Interpretation of media pH levels for container grown crops. Values are the same for all testing methods. Adapted from: W. Argo and P. Fisher. 2002. Understanding pH management of container grown crops, Meister Publishing, Willoughby, OH.
Acceptable range Examples Iron-inefficient Azalea, bacopa, Calibrachoa, dianthus, nemesia, pansy, petunia, rhododendron, or 5.4 to 6.2 snapdragons, verbena, vinca, and any other crop that is prone to micronutrient “Petunia” Group deficiency (particularly iron) when grown at high media pH. General Chrysanthemum, impatiens, ivy geranium, osteospermum, poinsettia, and any other 5.8 to 6.4 Group crop that is not generally affected by either micronutrient deficiencies or toxicities. Iron-efficient Lisianthus, marigolds, New Guinea impatiens, seed geraniums, zonal geraniums, and or 6.0 to 6.6 any other crop that is prone to micronutrient toxicity (particularly iron and manganese) “geranium” group when grown at low media pH
Table 2. Interpretation of media electroconductivity (EC) or soluble salt levels. For salt sensitive crops, like orchids, the low fertility level range would be a good starting point. Values are reported in mS/cm. 2:1 Saturated media Pour-thru Squeeze method extract method method method No fertility 0 – 0.25 0 to 0.75 0 to 1.0 0 to 1.0 Low fertility 0.30 to 0.75 1.0 to 2.0 1.0 to 2.5 1.0 to 2.5 Acceptable range 0.30 to 1.50 1.0 to 3.5 1.0 to 6.0 1.0 to 5.0 High fertility 0.75 to 1.50 2.5 to 3.5 4.0 to 6.0 2.5 to 5.0 Potential root damage >2.50 > 5.0 > 8.0 > 8.0 The units of measure for EC can be mMho/cm, dS/m, mS/cm, µM/cm, or mMho x 10-5/cm. The relationship is 1 mMho/cm=1 dS/m=1 mS/cm=1000 µS/cm=100 mMho x 10-5/cm.
Special Note: It is important to remember that EC is a measure of the total salt concentration in the extracted solution. It does not give an indication of the concentration of any of the plant nutrients. The only way to determine exactly what ions make up the EC is to use a more extensive commercial laboratory analysis.
Not for publication or reproduction without the authors consent. Pg. 5