ª 2014 by the Academy of Nutrition and Dietetics.

RESEARCH

Research and Practice Innovations

Vegetable Output and Cost Savings of CommunityGardens in San Jose, CaliforniaSusan J. Algert, PhD, RD; Aziz Baameur, MS; Marian J. Renvall, MS, RD

ARTICLE INFORMATION

Article history:Accepted 27 February 2014

Keywords:Community gardensUrban agricultureFood systems

Copyright ª 2014 by the Academy of Nutritionand Dietetics.2212-2672/$36.00http://dx.doi.org/10.1016/j.jand.2014.02.030

ABSTRACTUrban dwellers across the United States increasingly access a variety of fresh vegetablesthrough participation in neighborhood-level community gardens. Here we documentvegetable output and cost savings of community gardens in the city of San Jose, CA, tobetter understand the capacity of community gardens to affect food affordability in anurban setting. A convenience sample of 83 community gardeners in San Jose completeda background survey during spring and summer 2012. On average, gardeners were aged57 years and had a monthly income of $4,900; 25% had completed college. A repre-sentative subset of 10 gardeners was recruited to weigh vegetable output of their plotsusing portable electronic scales at three separate garden sites. Accuracy of each portablescale was verified by comparing the weight of a sample vegetable to weights obtainedusing a lab scale precise to 0.2 oz. Garden yields and cost savings were tabulated overallfor each plot. Results indicate that community garden practices are more similar tobiointensive high-production farming, producing 0.75 lb vegetables/sq ft, rather thanconventional agricultural practices, producing 0.60 lb/sq ft. Gardens produced onaverage 2.55 lb/plant and saved $435 per plot for the season. Results indicate that costsavings are greatest if vertical high value crops such as tomatoes and peppers are grownin community gardens, although yields depend on growing conditions, gardener’s skill,availability of water, and other factors. Future research is needed to document costsavings and yields for specific crops grown in community gardens.J Acad Nutr Diet. 2014;-:---.

THERE ARE MORE THAN 1 MILLION GARDENERS IN18,000 community gardens in the United States andCanada.1-3 Understanding the capacity of communitygardens to feed urban populations and improve their

nutrition depends on estimates of how much food can begrown in a given area. Studies documenting vegetable outputand associated cost savings of community gardens can pro-vide data to preserve existing gardens and promote thegrowth of new ones; however, the reliability of methods usedin documenting the amount of produce being grown in com-munity gardens has not been established or described indetail in the literature.4

Differences in vegetable production in community gar-dens can be due to a number of factors, including cropvariety, weather, soil conditions, seed species, gardener’sskill, and availability of water.5,6 Researchers have sug-gested that biointensive methods more closely resemblewhat community gardens practice rather than large-scaleindustrial farming.7 Data available from the US Depart-ment of Agriculture on conventionally grown crop pro-duction using commercial farming methods indicatesaverage yields of about 0.6 lb/sq ft for most vegetablesproduced in the United States. 5 Biointensive farming,which focuses on improving soil quality and organic, highyield methods produces approximately 0.83 to 0.95 lbvegetables/sq ft.5,7,8

The few studies that have documented crop yields fromcommunity gardens in the United States have reported highlyvariable results.5-9 The city of Philadelphia found that gar-deners were able to produce up to 1.4 lb/sq ft vegetables, anextremely high yield given plot sizes were small.9 However,gardeners were growing primarily tomatoes, a highly-productive vertical crop. The Farming Concrete projectdocumented that community gardens in New York City wereable to grow more than 1.2 lb/sq ft of produce.8 In contrast,the National Gardening Association (NGA) reported thatbackyard gardeners achieved a much lower average of0.5 lb/sq ft in small-scale food gardens.1 Similarly, an as-sessment of the potential for urban agriculture in Oakland,CA, found expected yields to be only about 0.46 lb/sq ft.4

The numerous benefits of community gardens includesavings over the cost of purchasing the same amount ofvegetables in a retail setting.8-12 Data on cost savings ofcommunity gardens is not readily available and what hasbeen published can vary widely. The Philadelphia study9

showed that garden plots yielded an average annual netvalue, after expenses, of $113.40. Other researchers estimateda cost savings of between $75 and $380 every seasonadjusted for inflation from 1994 to 2011.8

Previous research suggests that community gardeners eatmore vegetables, yet very little is known about the overalloutput of gardens in pounds harvested and associated cost

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savings.11-13 Therefore, we tested two hypotheses using re-sults from the weighing of vegetables in community gardens:the average harvest from the gardens would exceed by0.6 lb/sq ft the amount of produce typically grown usingconventional agricultural practices established by the USDepartment of Agriculture,5 and overall cost savings associ-ated with the amount of produce grown by communitygardeners would equal the $2/lb average in-season produceprices reported by the NGA.1 Our pilot study providesimportant additional data on the economic value of com-munity gardens in the western United States.

METHODSOur study was a partnership with the Parks, Recreation, andNeighborhood Services Department of the City of San Jose.The Department manages 18 community gardens on 35 acresserving more than 1,000 community gardeners. Part one ofthe study obtained a background survey of community gar-deners and part two recruited a subset of the survey partic-ipants to weigh produce output of their gardens during a4-month period.A pilot version of the survey was validated in 20 individuals

from a single community garden during March 2012. Therevised 30-question background survey was collected from aconvenience sample of 83 gardeners aged 18 years or olderrecruited from four separate community gardens during Aprilthrough September 2012. The survey was administered bythe investigators at the garden sites during times gardenerswere working on their plots. The University of CaliforniaInstitutional Review Board approved the study procedures,and study participants provided written informed consent.Participants were compensated for their time by receiving $5in incentives.The survey obtained background information on the gar-

deners, including crop types grown in their gardens. Thesecond part of this project documented the yield of vegeta-bles harvested from 10 community garden plots in threeseparate locations during the spring to summer 2012 seasonin San Jose. The 10 gardeners who weighed output of theirgardens were recruited as a subset of volunteers from thosewho completed the survey. The areas that were planted bythe gardeners varied in size from 100 to 600 sq ft.Gardeners who agreed to weigh produce received a

portable electronic scale that they could easily hang in thegarden (Chestnut Tools). The scale weighed in ounces andpounds. Accuracy of each scale was determined before dis-tribution to the 10 gardeners by weighing an object using theportable scale and comparing it with a more precise lab scaleaccurate to the 0.2 oz level (model SJ-12KHS; A & D electronicscale). Specifically, investigators compared weights of threedifferent tomatoes using each scale, and, in all 10 cases, theportable electronic scale weighed within 3% of the moreprecise electronic scale. Only vegetables were weighed forthis study.Our project borrowed from citizen science principles used

by the Farming Concrete crop weighing project in New YorkCity.8 Citizen scientists are lay volunteers who help to collectand analyze data as part of a researcher-led project.14 In thecase of our study, participation by nonscientists in designingand implementing the study improved garden participationand created a method easily replicated by other projects. The

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citizen scientists who committed to weighing produce in thisstudy were involved in decision-making regarding data-collection methods such as the preferred choice of scale forweighing and the use of results.The citizen scientists were experienced gardeners,

including five Cooperative Extension master gardeners, twoCooperative Extension master composters, a computer engi-neer, a retired teacher, and an administrative assistant. Threeof the 10 had <5 years’ experience as gardeners, four had 6 to10 years’ experience gardening, and three had �11 years’experience. Each citizen scientist gardener was given a dailylog in which to record the produce that was harvested andweighed in the garden. The investigator or assistant was inweekly communication with the citizen scientists to deter-mine compliance and review log entries for accuracy andcompleteness. The logs were collected every 2 to 4 weeks for4 months and data was entered into an Excel spreadsheet(Microsoft Corp) by the investigator.Each citizen scientist gardener weighing produce was

compensated with a $20 gift card before, during, and at theend of the study. The amount spent on overhead for eachgarden, including plants, seeds, fertilizers, tools, and soilamendment was recorded from memory by the citizen sci-entist gardeners. The itemized overhead costs were recordedin logs and reviewed for completeness by investigators.Overhead costs of individual garden plots varied widelybecause compost was provided free of charge, tools werepurchased collectively, and many gardeners planted seedsfrom a previous year.Yields for each crop were tabulated as total pounds, pounds

per plant, and pounds per square foot, including means andstandard deviations. Average retail prices for produce werecalculated using data obtained from the Bureau of LaborStatistics for the western region 2012 for tomatoes, lettuce,peppers, and broccoli.15 Average prices for all other vegeta-bles were obtained from a local grocery store in the San Josearea during November 2012. Prices were considered com-parable to what participants would pay in a local retail outlet.

RESULTSThe summary of the demographic data for the 83 gardenersindicates that the subset of 10 citizen scientist gardeners whoweighed produce were closely representative of the overallgroup completing the survey. The average age of surveyparticipants was 57 years, and the average age of the groupweighing produce was 60 years. Educational background wassimilar for survey respondents and the citizen scientist gar-deners: 30% had completed high school and 25% hadcompleted college. Income ranged widely but averaged$4,900 per month for survey respondents and $4,000 permonth for the 10 citizen scientist gardeners weighingproduce.Due to the high level of commitment and engagement in

the research study, all 10 citizen scientist gardeners com-pleted the study. As depicted in the Table, the 0.75 lb/sq ftvegetables harvested from the community gardens in ourpilot study were more similar to the 0.83 to 0.95 lb/sq ftvegetables from biointensive farming practices than the0.60 lb/sq ft typical of conventional agriculture. The mostcommon crops grown by gardeners in descending orderincluded tomatoes, squash, green beans, peppers, onions,

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Table. Results of weighed gardens’ vegetable production and potential cost savings of 10 citizen scientist gardeners

ParticipantWeightproduced (lb)

Weightper/sq ft (lb)

Weightper plant (lb)

Totalsavings ($) Savings/lb ($)

1 593 0.97 3.1 786.57 1.33

2 411.8 0.69 2.75 586 1.42

3 356.22 0.71 2.37 619.27 1.74

4 339 0.85 2.82 580.6 1.71

5 295.8 0.49 2.46 375 1.28

6 265.8 0.45 2.3 403.1 1.52

7 262.21 0.66 3.2 391.9 1.49

8 163.34 1.13 2.47 319 1.95

9 150 0.75 2.5 197.42 1.32

10 84.6 0.84 1.52 126 1.49

Mean 292.18 0.75 2.55 438.49 1.53

Mean�standard deviation 292.1�146.2 0.75�0.20 2.5�0.47 435�203 1.5�0.2

RESEARCH

eggplants, and cucumbers. Two of the most common crops—tomatoes and green beans—were grown vertically, whichcontributed to a higher output per square foot and mayexplain, in part, the higher output per square foot overall bygardeners in our study.The estimate of the cost savings of community gardens

found in the Table is based on the total number of pounds ofproduce grown in the garden. The average savings of vege-tables harvested from gardens in this study was $1.53/lb,which was slightly less than the standard of $2/lb reported bythe NGA. The gardeners saved an average of $435 per plot forthe 4-month season.

DISCUSSIONAverage cost savings per community garden plot was higherin our study than results reported by other researchers,although savings were less than the $2/lb cited as an averageby the NGA.1 The prices are a rough estimate intended pri-marily for comparison purposes. Garden output and theassociated cost savings can vary widely based on a multitudeof factors cited previously; however, the results suggest thatcost savings from growing one’s own vegetables can besubstantial.One criticism of comparing cost savings of community

garden output to retail prices is that the cost of labor bygardeners is not factored in. Intensively-farmed land requiresa great deal more labor per square foot than conventionalagriculture. If labor invested in community gardens is takeninto consideration, the cost of produce could be considerablyhigher. However, the often-cited benefits of community gar-dens include community cohesion, improved health, andcross-cultural sharing of food, all factors that are hard toquantify when making a comparison to other forms of urbanagriculture.16-21

The Farming Concrete project in New York was the firsturban garden project to weigh produce output and report

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results in pounds per plant in addition to pounds per squarefoot.8 The authors make the point that reporting weights byplant rather than by square foot is more informative becausecommunity gardeners most often tend their own plots withmultiple crops in each bed. It is easier for a gardener to countthe number of plants than to count the square foot coverageof each plant or the entire bed. This is especially true withintensive growing and with the use of vertical crops such astomatoes. Reporting crop output by plant is also a usefulmethod for comparing vegetable output between plots aswell as overall plot output in a community garden.Greater accuracy in determining the size of the plot dedi-

cated to specific crops might produce more significant find-ings than calculating overall garden output for all cropvarieties grown. For example, calculating pounds per squarefoot dedicated just to one crop such as tomatoes could likelyshow a relationship between size of plot planted and output.Vertical growing of high-yield, higher-value vegetables suchas tomatoes, cucumbers, and peppers, provides the greatestcost savings. Future studies need to determine plot sizedevoted to specific crops to determine whether there is arelationship between pounds harvested, cost savings, andsquare footage in community gardens.The use of a small convenience sample in one geographic

region limits the generalizability of our study findings. Thehigher degree of error with lighter-weight produce wouldincrease error for those gardeners planting vegetables such aslettuce, herbs, and greens. The portable scale used in thisproject is most accurate for use in weighing output of heaviervegetables such as tomatoes, squash, cucumbers, beans, on-ions, potatoes, corn, and eggplants.Results may also be limited by the self-selection of the

gardeners to participate in both the survey and weighingprojects.Our study included only gardeners with between 4 and 25

years’ experience. Novice gardeners would likely requireadditional training and oversight to commit to weighing

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RESEARCH

projects similar to this one. We have a study under way withnovice backyard gardeners from low-income neighborhoodswho are weighing produce output. That study will determinewhether novice gardeners need more supervision and sup-port to ensure data collection is complete and reliable.

CONCLUSIONSOur study found that community garden practices are moresimilar to biointensive high-production farming producing0.75 lb vegetables/sq ft, rather than to conventional agricul-tural practices, producing 0.6 lb/vegetables/sq ft. We describein detail an easily reproducible method to quantify cropyields using a portable electronic scale, which empowersgardeners to track output and cost savings of their gardensthemselves. More data are needed to extrapolate findings tocommunity gardens on a larger scale, including variability ofoutput with seasonal variations, crop rotations and varieties,and environmental conditions. Cost savings may be sub-stantial if vertical high value crops are grown in communitygarden plots.Documenting the harvests of urban community gardens

helps to define their roles in the local food economy, partic-ularly when yields are monetized, because most of the pro-duction and consumption takes place in the informaleconomy and is not otherwise tracked. The method used inour study of reporting vegetables harvested in pounds persquare foot and pounds per plant provides data on cost sav-ings in community gardens. Future research is needed todocument cost savings and yields for specific crops grown incommunity gardens to determine the economic influence ofcommunity gardens in areas where fresh vegetable intakecan be limited, of poor quality, and/or of low culturalrelevance.

References1. National Gardening Association. The impact of home and community

gardening. 2009. http://www.gardenresearch.com/files/2009-Impact-of-Gardening-in-America-White-Paper.pdf. Accessed December 4,2013.

2. Birky J. The modern community garden movement in theUnited States: Its roots, current conditions and prospects for thefuture. 2009. http://scholarcommons.usf.edu/cgi/viewcontent.cgi?article¼2859&context¼etd. Accessed February 25, 2014.

3. American Community Garden Association. Binational communitygarden database. http://acga.localharvest.org/. Accessed February25, 2014.

4. McClintock N, Cooper J. Cultivating the Commons: An Assessment ofthe Potential for Urban Agriculture on Oakland’s Public Lands. Berkeley,CA: University of California Berkeley; 2009.

5. Columbia University Earth Institute. The potential for urban agri-culture in New York City, 2012. http://www.urbandesignlab.

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columbia.edu/sitefiles/file/urban_agriculture_nyc.pdf. AccessedDecember 19, 2013.

6. Brown KH. Urban agriculture and community food securityin the United States: Farming from the city center to the urbanfringe. 2002. http://foodsecurity.org/PrimerCFSCUAC.pdf. AccessedFebruary 25, 2014.

7. Jeavons J. How to Grow More Vegetables than You Ever Thought on LessLand than You Can Imagine. 7th ed. Berkeley, CA: Ten Speed Press;2006.

8. Gittleman M, Jordan K, Brelsford, E. Using citizen science to quantifycommunity garden crop yields. http://digitalcommons.lmu.edu/cgi/viewcontent.cgi?article¼1095&context¼cate. Accessed December17, 2013

9. Vitiello D, Nairn M. Community Gardening in Philadelphia, 2008.Philadelphia, PA: Penn Planning and Urban Studies of the Universityof Pennsylvania; 2009.

10. Blair D, Giesecke CC, Sherman S. A dietary, social and economicevaluation of the Philadelphia urban gardening project. J Nutr Educ.1991;23:161-167.

11. Carney PA, Hamada JL, Rdesinski R, et al. Impact of communitygardening project on vegetable intake, food security and family re-lationships: A community based participatory research study.J Commun Health. 2012;37(4):874-881.

12. Litt JS, Soobader MJ, Turbin MS, et al. The influence of socialinvolvement, neighborhood aesthetics and community gardenparticipation on fruit and vegetable consumption. Am J Public Health.2011;101(6):1466-1472.

13. Alamo K, Packnett E, Miles RA, et al. Fruit and vegetable intakeamong urban community gardeners. J Nutr Educ Behav. 2008;40:94-101.

14. Gura T. Citizen science: Amateur experts. Nature. 2013;496(7444):259-261.

15. Bureau of Labor Statistics. Average retail and energy prices, US cityaverage and West region 2012. http://www.bls.gov/ro3/apwe.htm.Accessed December 13, 2013.

16. Saldivar-Tanaka L, Krasny M. Culturing community development,neighborhood open space, and civic agriculture: The case of Latinocommunity gardens in New York City. J Agr Human Values. 2004;21:399-412.

17. Hale J, Knapp C, Bardwell L, et al. Connecting food environments andhealth through the relational nature of aesthetics; gaining insightthrough the community gardening experience. Soc Sci Med. 2011;72:1853-1863.

18. Comstock N, Dickinson M, Marshall JA, et al. Neighborhoodattachment and its correlates: Exploring neighborhood conditions,collective efficacy and gardening. J Environ Psychol. 2010;30:435-442.

19. Tieg E, Amulya J, Bardwell L, et al. Collective efficacy in Denver,Colorado: Strengthening neighborhoods and health through com-munity gardens. Health Place. 2009;15:1115-1122.

20. MacRae R, Gallant E, Patel S, et al. Could Toronto provide 10% of itsfresh vegetable requirements from within its own boundaries?Matching consumption requirements with growing spaces. http://dx.doi.org/10.5304/jafscd.2012.022.002. Accessed March 16, 2014.

21. Van de Berg AE, Van Winsum-Westra M, De Vries S, et al. Allotmentgardening and health: A comparative survey among allotment gar-deners and their neighbors without an allotment. J Environ Health.2010;9:74.

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AUTHOR INFORMATIONS. J. Algert is a nutrition advisor and A. Baameur is a small farm advisor, University of California Cooperative Extension Santa Clara County,San Jose. M. J. Renvall is a biostatistician in private practice, El Cajon, CA.

Address correspondence to: Susan J. Algert, PhD, RD, University of California Cooperative Extension Santa Clara County, 1553 Berger Dr, Bldg,1 Floor 2, San Jose, CA 95112. E-mail: salgert@ucanr.edu

STATEMENT OF POTENTIAL CONFLICT OF INTERESTNo potential conflict of interest was reported by the authors.

FUNDING/SUPPORTThis study received funding from the University of California Division of Agriculture and Natural Resources.

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