Our project demonstrates the viability of logs from invasive trees to produce shiitake mushrooms on small farms in North Florida and South Georgia. This year, two farms successfully produced shiitake mushrooms on both Chinese tallow and oak logs. Yield varied by farm, mushroom strain, and log species. No mushrooms of either strain were produced on Chinaberry or mimosa logs.
Summary: A comparison of edible shiitake mushroom production on logs of native oak versus non-native invasive weed-trees identified Chinese tallowtree as a feasible alternative on small farms in North Florida. Although overall yield on oak logs was higher, based on total number and total weight of shiitake mushrooms, the weight of individual Chinese tallowtree mushrooms was significantly larger than an oak derived mushroom. Two other non-native trees evaluated for shiitake mushroom production, Chinaberry and mimosa, failed to produce mushrooms. Edible mushroom fungi can be used to recycle invasive non-native trees and transform this detrimental resource into an income producing, natural resource.
Project Objectives: Removal of invasive species, especially trees, is often time consuming and expensive. Even for a private landowner or small farmer, the cost of cutting down invasive trees and removing the waste generated by branches and trunks consumes resources in time, effort, personnel, and finances; negatively impacting farm sustainability. In an effort to help offset some of these expenditures for small farmers, our overall objective was to evaluate the potential of using non-native tree logs, common to the southern region, to produce edible and marketable mushrooms. We proposed to turn unsustainable, non-native tree species into a sustainable, small farm commodity. Three invasive species were targeted in this study: Chinese tallowtree (Triadica sebifera), mimosa tree (Albizia julibrissin) and Chinaberry tree (Melia azedarach).
This two year study addressed three objectives:
1) Determine the yield of edible mushrooms (shiitake) on logs of four tree species common in the southeastern USA (three non-native invasive species and native oak species);
2) Determine the economic profitability for small farmers in marketing edible mushrooms;
3) Provide hands-on training to farmers on growing mushrooms on invasive tree species.
Our initial Objective 1 submitted with the grant request was to evaluate the yield of two commercially grown fungi species; golden oyster (Pleurotus cornucopiae) and shiitake (Lentinula edodes). Because data collected from a pilot study initiated in 2014 identified poor production on oak from the golden oyster fungi, a second strain of shiitake was substituted for the golden oyster. Logs of all test tree species were inoculated with one of two shiitake varieties, Wide Range (WR) 46TM or Snow CapTM. Significant differences in mushroom production between the two shiitake strains were not found so the results from the two strains were combined and only WR 46 was used in the second year inoculation.
Objective 2 economic data relating to the sale of mushrooms was collected by the farmers. Farmers sold shiitake mushrooms primarily at several Farmer’s Markets, but also to Community Sustainable Agriculture (CSA) members, small local food stores, and at road-side stands.
Efforts on the third objective included the training of four farms in shiitake production on logs, establishment of mushroom production shade houses, and posting of photos and short videos on farmer websites of the project to produce edible mushrooms on non-native tree logs.
Log Preparation and Inoculation Process: The following four steps were followed for all logs in the study and proved successful in producing edible mushrooms on acceptable tree species.
Step 1 – Log preparation. Trees used for mycelium substrate were identified from woodlots, fencerows, and waste areas at farms cooperating in this study and adjacent properties. Trees were cut in February-March when the sapwood was rich in sugars and before foliation. Cut stumps of invasive species were treated with Garlon 3A immediately after cutting to kill roots and prevent sprouting (Miller et al. 2010). Trunks were cut into 3ft long logs of 4-8in diameter. Once logs were felled, they were kept away from soil to avoid contamination with saprophytic fungi and handled in a manner to not damage the bark layer (Stamets and Chilton 1983). Logs were stacked on pallets, kept close to the ground, and shaded for a 2-3 week period before inoculation. This “resting” period allowed antifungal properties of the wood to dissipate (Stamets 2005).
Step 2 – Inoculation: Before inoculation, the log surface was lightly cleaned with a wire brush to remove soil, algae, lichens, and insect eggs. Catalogues of mycelium spawn producers/sellers generally suggest 45-50 spawn plugs per 3ft x 6in log (Field & Forest Products 2017, Fungi Perfecti 2017). Our inoculation rate was based on the surface area of this “standard log”: (S = 2Πrh = 678 in2), where r = log radius and h = log height. Therefore, assuming a 6in diameter log received 50 plugs, each inch change in log diameter correlated to an increase (or decrease) of 8 plugs (Table 1). FinalReport_SSARE_OS14-086_Table1 The number of plugs/log was determined, the information recorded, and each log marked with an aluminum tag containing a unique number, tree species, and randomly selected fungus treatment (shiitake strain). Evenly spaced holes (5/16 in diameter x 1in deep) were power drilled into each log 4in apart arranged longitudinally down the log axis in a diamond pattern (Stamets 2000). Each hole was “plugged” with a dowel inoculated with mycelia of the appropriate species, then sealed with a layer of soy wax to conserve moisture and prevent infection by competing organisms.
Step 3 – Incubation: Inoculated logs were stacked on pallets under shade for 7 months to allow the spawn to fully colonize the logs. Logs were watered using a sprinkler system during the summer incubation period as needed to support mycelium growth. Supplemental watering in our humid southern climate was required only once per week during dry spells.
Step 4 – Production: “Initiating” the logs took place in October, nearly 8 months after inoculation. Mycelium growth in the logs was visible at either cut face as a mottling pattern. Each log was removed from the pallet stack and soaked in a tank of water for 24 hr before being placed along a fence in an “A-Frame” manner. The fence was constructed of wire stretched between fence posts and a short platform to keep the log base away from the soil. Logs were spaced to allow access to all surfaces for mushroom harvesting. Mushroom primordia started forming within 2 weeks of initiation. Mushrooms formed throughout the log surface, not only the spawn plugged holes. Logs were watered as needed to maintain moisture and generally soaked every 6 weeks to stimulate mushroom production.
Pilot Study: In February 2014, a pilot study was initiated to evaluate the ability of two common fungi species to successfully inoculate logs from three invasive tree species and produce edible mushrooms. To evaluate our log inoculation technique, we also included a mix of the native oak species, Q. nigra and Q. laurifolia, commonly used by small farm shiitake cultivators in north Florida. The two common fungi species used for mushroom cultivation were a native Florida variety of oyster mushroom, P. ostreatus var. florida, a preferred variety for southern climates because it fruits at warmer temperatures (Stamets 2000), and shiitake, Lentinula edodes (Berk.) Pegler. The three non-native tree species were paperbark, Melaleuca quinquenervia (Cav.) S.T. Blake, tallow, and earleaf acacia, Acacia auriculiformis A. Cunn. ex Benth. Although mycelial growth was recorded on all four species of trees during summer 2014, only shiitake mushroom fruiting occurred in fall 2014. No mushrooms occurred on acacia, only a few mushrooms occurred on paperbark, but a substantial production of shiitake was gathered from oak and tallow.
First Year Study: Based on results from the 2014 pilot study, our inoculation and storage techniques were proper and we successfully produced mushrooms in the north Florida region. Deviations from the pilot study that were made for the first year study included the use of non-native tree species found in the north Florida region and inoculation with only shiitake spawn. Logs from three species of non-native invasive trees were used in the first year study:
1) Chinese tallowtree, Triadica sebifera (L.) Small, was introduced into Georgia in the late 1700’s and is now invasive throughout the southeastern USA where it forms dense stands in mesic prairies, and floodplain forests (Jubinsky and Anderson 1996). It is listed as a Category I “most invasive plant species” by the Florida Exotic Pest Plant Council (FLEPPC 2011). Chinese tallow is considered a Noxious Weed by the Florida Department of Agriculture and Consumer Services (FDACS), meaning propagation, commerce, and transport is prohibited (McCormick 2005).
2) Mimosa tree, Albizia julibrissin Durazz., was introduced from China to the USA in 1745 and Florida in 1883, and is widely cultivated as an ornamental (Lakeland et al. 2008). However, due to its tendency to readily establish in a variety of habitats after escaping from cultivation, mimosa is considered a Category I “most invasive plant species” by the FLEPPC (FLEPPC 2011). Restrictions on planting exist in Okaloosa and Seminole counties in Florida (Lakeland et al. 2008).
3) Chinaberry tree, Melia azedarach L., was released in the early 1800s as an ornamental, planted in many southern states, and now occurs north to Virginia and west to Oklahoma (Langeland et al. 2005). Chinaberry occurs primarily in disturbed areas (right-of-ways and fencerows), but also invades floodplain hammocks, marshes, and upland woods (Langeland et al. 2005), and is listed as a Florida Category II invasive that has “increased in abundance … but not yet altered Florida plant communities” (FLEPPC 2011). Fruits are highly poisonous if ingested by humans, but birds readily spread the seeds without harm (Russell et al. 1997).
Logs of each of the three non-native species and logs of oak were harvested, inoculated, and stored at two cooperating small farms; Full Earth Farm, Quincy, FL, and Little Eden Heirloom Farm, Crawfordsville, FL. Our target number of logs for each tree species at each farm was 20 (Table 2A). Tallow was included in this first year to insure mushroom production on a non-native species; we were unaware of mushroom production trials on Chinaberry or mimosa. Logs of all test tree species were inoculated with one of two shiitake varieties, Wide Range (WR) 46TM or Snow CapTM. Each farm received 80 logs, divided into eight treatments (10 logs/tree species/shiitake strain) (Table 2A). Logs were processed in the manner explained above.
Second Year Study: In the projects’ second year, the non-native tree species and shiitake fungus variety combination identified with the highest yield during the previous year was selected for mushroom production, and our efforts were focused on training additional farmers and demonstrating potential commercial production. Since both Chinaberry and mimosa failed to produce even one shiitake mushroom and the production by the two shiitake strains were not significantly different, the second year study was conducted on tallow and oak logs with only the Wide Range (WR) 46TM shiitake strain. Two additional cooperating small farms were added to the study; Sanguan Asian Herbs, Climax, GA, and Artzi Farm, Thomasville, GA. A goal of 40 logs of oak and 40 logs of tallow (Table 2B) were harvested, inoculated, and stored at each of the four farms using the same process as explained above.
Data Analysis: Mushrooms were harvested by log, counted, weighed (as daily production per log), and the information recorded. Since no mushrooms were produced on any of the Chinaberry or mimosa logs, logs of these tree species were removed from data analysis. Data from logs inoculated in the first and second year studies were combined. For each of the three farms in which data were collected, the experimental design was a completely randomized design with two levels of replication; multiple trees for each log species and multiple logs from each tree. For each inoculation year and harvest period, analysis of variance (ANOVA) was performed on data combined over farms with farm and farm by trees species interactions treated as fixed effects with the diameter of each tree log as a covariate. ANOVA of mushroom size (weight per mushroom) and log transformed mushroom weight used a general linear mixed model. Analysis of number of mushrooms used a generalized linear mixed model with a negative binomial distribution and a log link function. Mean yield values were computed by farm, tree species, and inoculation year and harvest period and compared using the means separation test of LSD pairwise comparison. Tallow and oak logs that did not fruit were not included in this analysis. The probability and associated confidence interval that logs at each farm would produce mushrooms was computed for all the logs and compared with a chi square test. Measures of central tendency were presented as means ± SEM.
Economic Investigation: Full Earth Farm, Little Eden Heirloom Farm, and Artzi Farm have produced vegetables for several years and have established markets for their products. Their various market types allowed assemblage of economic information immediately upon mushroom harvest. When a farmer marketed their edible mushrooms, they recorded the following information: date-of-sale, establishment name, market type, mushroom weight sold, and income. Comparisons were made of income earned by market type and mushroom species. Income in the second year of this project was expected to be higher due to the use of host logs identified the first year to be most productive and a second year of production from the first year logs.
The first year study logs were inoculated in late winter 2015 and mushrooms were harvested during two periods; fall of 2015 through winter of 2016, and fall of 2016 through winter 2017. The second year study logs were inoculated in late winter 2016 and harvest data were collected for this project only during the period of fall 2016 through winter 2017. Shiitake mushroom yield comparisons presented in this report between logs of oak and tallow were made for both inoculation years and all three harvest periods. A detailed time-line of the inoculation and harvest process is presented below:
First Year Study Logs (2015-2017)
March: Trees were felled, cut to length (3 feet), inoculated with shiitake plug mycelium (Fig. 1), and stacked in the shade on pallets.
March-October: Logs were irrigated as needed to prevent drying.
May: A shade cloth, hoop house was constructed at each farm to store inoculated logs. Logs were stacked on wood pallets in crisscross manner under shade house and irrigation repositioned for watering logs as needed (Fig 2).
September: Log stacking fences were constructed under each shade cloth, hoop house (Fig. 2), logs were moved from pallets to stacking fence, and irrigation reassembled.
October: Mushrooms began to form on logs (Fig. 3). Mushrooms were harvested, data were collected, and mushrooms were sold from YEAR-1-LOGS.
October-March 2016: Mushrooms were harvested and production data collected by farmers; mushrooms sold; mushroom sales economic data collected by various outlets.
April-October: Logs remained under shade house, along stacking fence, and were irrigated as needed to prevent drying.
September-March 2017: Mushrooms were harvested, data were collected, and initial mushrooms were sold from YEAR-1-LOGS.
Second Year Study Logs (2016-2017)
February: Trees were felled, cut to length (3 feet), inoculated with shiitake mycelium, and stacked in the shade on pallets.
March-October: Logs were irrigated as needed to prevent drying.
May: Logs were stacked on wood pallets in crisscross manner under shade house and irrigation repositioned for watering logs as needed.
September: Additional log stacking fences were constructed under each shade cloth, hoop house, logs were moved from pallets to stacking fence, and irrigation reassembled.
October: Mushrooms began to form on logs. Mushrooms were harvested, data were collected, and mushrooms were sold from YEAR-2-LOGS.
October-March 2017: Mushrooms were harvested and production data collected by farmers; mushrooms sold; mushroom sales economic data collected by various outlets.
The overall production of shiitake mushrooms on logs of the two tree species revealed that oak logs produced significantly more mushrooms than tallow logs for both yield measurements of mean weight of mushrooms produced (Fig. 4) and mean number of mushrooms produced (Fig. 5). However, the mean weight of an individual mushroom was significantly larger for tallow logs than oak logs (Fig. 6). FinalReport_SSARE_OS14-086_Graphs
Economic Analysis — One of the farms brought into the study during the second year failed to collect data for the research project. At the remaining three farms, farmers sold all the mushrooms that they produced; the vast majority of mushrooms (over 95% of sales) were sold at farmers’ markets. The financial gain that each farm made on mushrooms was determined for oak produced and tallow produced shiitake mushrooms at the rate of $16/pound (Table 3). FinalReport_SSARE_OS14-086_Table3 The harvest period for shiitake mushrooms started in October when the nights began to cool and continued through March when the temperatures warmed. Production and income was greater the second harvest period because additional logs were added the second year of the project.
Altieri, M.A. 1995. Agroecology: The Science of Sustainable Agriculture. Westview Press, Boulder, CO.
Baran, J.K. 2010. Field study of a technique for combining low-cost, herbicide-free control of woody invasives, in particular Ailanthus altissima, with production of edible mushrooms. Final Report FNC07-670-07, NCR-SARE Farmer Rancher Grant Program, University of Nebraska, Lincoln, NE.
EddMapS. 2017. Early Detection and Distribution Mapping System, http://www.eddmaps.org.
Field & Forest Products. 2017. Specialty Mushrooms, 2017 Spawn and Supply Catalog. http://www.fieldforest.net/
FLEPPC. 2011. Florida Exotic Pest Plant Council’s 2011 list of invasive plant species. Wildland Weeds 14:11-14.
FLEPPC. 2014. Invasives 101. http://www.fleppc.org/FLEPPC_main.htm
Fungi Perfecti. 2017. From the Forest, to Our Farm, to You! http://www.fungi.com/
Langeland, K.A., and K.C. Burks (eds.). 2005. Melia azedarach, pp. 96-97. In Identification and Biology of Non-Native Plants in Florida’s Natural Areas. University Florida, Gainesville, FL.
Langeland, K.A., H.M. Cherry, C.M. McCormick, and K.A. Craddock-Burks (eds.). 2008. Albizia julibrissin Durazz., p. 76. In Identification and Biology of Nonnative Plants in Florida’s Natural Areas, 2nd Edition. IFAS Publication SP 257, University of Florida, Gainesville, FL.
Russell, A.B., J.W. Hardin, and L. Grand. 1997. Melia azedarach. In Poisonous Plants of North Carolina. NC State University, Raleigh, NC. http://plants.ces.ncsu.edu/plants/poisonous-plants/melia-azedarach/
Stamets, P. 2000. Growing gourmet and medicinal mushrooms, 3rd ed. Ten Speed Press, Berkely, CA.
Stamets, P. 2005. Mycelium Running: How mushrooms can help save the world. Ten Speed Press, Berkely, CA.
Educational & Outreach Activities
(1) Publication (in progress): Hight, S.D., K. Bowers, N. Miller, and J. Taylor. Use of non-native invasive tree logs for commercial mushroom production on small farms. Natural Areas Journal OR Weed Technology.
(2) Video (undergoing final editing) of log inoculation event at Full Earth Farm during second year of project. Video includes short narration of research project, instruction and discussion of mushroom inoculation by farmer, and documentation of various inoculation steps.
(3) Market Square Farmers Market Demonstration, Tallahassee, FL, 5 November 2016. The shiitake mushroom inoculation procedure was explained and demonstrated to Market shoppers, and a local high school culinary arts class conducted a “Cooking with Shiitake Mushrooms” demonstration and tasting. Two dishes were prepared by a high school student during the three hour demonstration; 1) Sautéed Shiitake Mushrooms, and 2) Orzo Pasta with Shiitake Mushrooms and Basil. Recipes of both dishes and a list of mushroom “Fun Facts” was printed and made available to audience members. A variety of questions were answered on mushroom inoculation and mushroom cooking. In addition, attendees were encouraged to participate in a drawing for a free pound of shiitake mushrooms. Eighteen attendees filled out a brief form that consisted of two questions about mushroom production on logs and their name and contact information. Ten winners were randomly selected and they picked up their free mushrooms at the market at a later date. Shiitake-Mushroom-Recipe-Facts-Sheet_SHedit
(4) Poster presented at Market Square Farmers’ Market Demonstration, 5 November 2016.
(5) Shiitake and Oyster Mushroom Workshop at Small Farms Academy, Suwannee Valley Extension Station, IFAS, Live Oak, Florida, 10 February 2017. Fifteen minute presentation was made about the project to produce shiitake mushrooms on logs of non-native trees. Several questions by attendees were answered after the presentation and during a discussion period at the end of the workshop. Workshop attended by over 50 small scale farmers in the North Florida and South Georgia area.
(6) Educational experience at Montford Middle School, Tallahassee, FL, 6th Grade class, 10 March 2017. Presentation on the steps of inoculating logs with shiitake mushroom spawn was made to the class. Information on the problems of non-native weedy species and the use of non-native logs in the project were presented and discussed with the students. Logs that had been pre-drilled were brought to the class so the students could have an on-hands experience of pounding mycelium coated wood plugs into the holes and covering them with melted soy wax. Logs remained at the school for the students to observe during next year’s harvest season.
(1) Invasive trees were removed from farms and surrounding locations for use in mushroom production.
(2) Chinese tallowtree, listed as a Florida Category 1 Invasive Species (“most invasive plant species”), produced edible shiitake mushrooms. Although the number of mushrooms was fewer on Chinese tallowtree logs than on oak logs, the weight of individual mushrooms was greater on Chinese tallowtree than oak.
(3) Four invasive tree species were deemed unsuitable for shiitake mushroom production – paperbark, earleaf acacia, Chinaberry, and mimosa.
(4) Shiitake mushrooms were harvested, counted, weighed and subsequently sold by the farmers primarily at weekly markets, but also at roadside stands, in CSA baskets, and small local food stores from October 2015 to April 2017.
Farmer Adoption — Three out of four farmers that participated in the project had not cultivated shiitake mushrooms previously. All of the farmers who participated indicated that they planned to continue cultivating the mushrooms in the future. The two farms added in the second year of the project had difficulty fulfilling their data collection responsibilities; one farm completely failed to record their mushroom harvest, and the other farm only recorded mushroom production for the first three months of the harvest period, failing to record the remaining three months of the production period.
Agricultural Sustainability — This project addressed three of the SARE On-Farm Focus Areas; alternative crops, sustainable marketing projects, and increasing sustainability of existing farming practices.
Sustainable agriculture can be understood as an ecosystem approach to agriculture (Altieri 1995). Many farmers are adopting sustainable practices with the goals of reducing input costs, preserving the resource base, and protecting human health. The center point of a sustainable farming operation is not the rejection of conventional practices, but the incorporation of innovative sustainable practices. Sustainable systems integrate and take advantage of naturally occurring beneficial interactions. The objective is to sustain and enhance rather than reduce and simplify the biological interactions, thereby reducing harmful off-farm effects of production practices. Sustainable farms produce crops without relying on chemical pesticides, synthetic fertilizers, genetically modified seeds, or practices that degrade soil, water, or other natural resources. By growing a variety of produce and using diversified production techniques, sustainable farms protect biodiversity and foster the development and maintenance of healthy ecosystems.
Our mushroom project makes agriculture in the southeastern US more sustainable by
(1) adding a niche market commodity to small farmers’ production array,
(2) enhancing the environmental quality of small farmer land by managing non-native, invasive, weedy trees,
(3) efficiently using on-farm resources integrated with natural biological cycles,
(4) increasing economic viability of farm production by creating a high value commodity grown on a small scale, and sold locally,
(5) enhancing the quality of life for small farmers and their customers that purchase their edible mushrooms, and
(6) building the capacity of small farmers to succeed through relevant education and hands-on training.
The way that crops are sold must be accounted for in the sustainability equation. Food sold locally does not require additional energy for transportation (including consumers). Our project sought to maximize the “local food system” by producing and distributing a local commodity close to consumers’ homes. We evaluated the income earned by small farmers at various local avenues which small farmers in this region access to sale their mushroom product to consumers.
The advantage of log mushroom culture is that it is a simple and natural method. Log mushroom culture was developed in Asia over a thousand years ago, and even today, thousands of small-scale shiitake growers use log culture to provide the majority of mushrooms sold to markets (Stamens 2000). These growers supply local markets with their product, generating an income for their families. Yet, to date, the local production of mushrooms largely remains a vast, untapped resource in the US (Stamens 2000).
As an alternative to burning non-native invasive trees (which causes pollution, sudden emissions of carbon dioxide, and denitrification of soil) growing fungi on wood allows for the incorporation of nutrients back into the ecosystem, improvement in soil structure, and the gradual release of carbon dioxide. Fungi are the premier recyclers of organic wastes and they efficiently return nutrients back into the ecosystem. Utilizing edible mushroom fungi to recycle invasive non-native trees transforms a detrimental constituent on small farms into an income producing natural resource.
Areas Needing Additional Study
(1) Conduct additional screening of other non-native tree species for their ability to produce edible mushrooms.
(2) Although no information was found on negative effects to humans from eating mushrooms produced from plant species containing potentially toxic chemicals, no negative aspects were experienced by eating mushrooms produced on tallow logs. In addition, assumptions made about the non-toxicity of logs that served as mushroom producing media included 1) plant chemicals that serve as non-herbivore deterrents occurred primarily in the leaves and reproductive structures of the plants, not the wood, 2) if high levels of toxins were present in the wood, then they would interfere with the growth and survival of mycelium, preventing the formation of mushrooms (which was probably true for Chinaberry), and 3) commercially marketed edible mushrooms are safely produced on tree log species (i.e., black cherry, Prunus serotina Ehrh.) that contain toxic chemicals without detrimental effects regarding human consumption. However, an additional line of research could be the identification and quantification of various compounds in mushrooms grown from various tree species’ logs and/or other media (i.e. wood shavings).