Published by City Farmer, Canada's Office of Urban Agriculture


A Dietary, Social and Economic Evaluation of the Philadelphia Urban Gardening Project

By Dorothy Blair, Carol C. Giesecke, And Sandra Sherman

Nutrition Department, College of Health and Human Development, The Pennsylvania State University, University Park, PennsyIvania 16802; and National Child Nutrition Project, 1501 Cherry St.,Philadelphia, Pennsylvania 19106

Used with the permission of Carol C. Giesecke
This Web version does not include tables and footnotes. They can be found in The Journal of Nutrition Education, July/Aug, 1991 (JNE 23:161-167, 1991)


To evaluate the Philadelphia Urhan Gardening Project. 144 gardeners were selected from a stratified random sample of garden sites throughout the city. Sixty-seven non-gardening controls were selected from thc neighborhoods surrounding these sites. Data collected during home or garden interviews included demographic variables, food frequencies and dietary habits, measures of life satisfaction, and neighbor-hood involvement. The yield of 151 garden plots was assessed and the economic value calculated, based on retail produce prices. Garden sites yielded an average of $160 worth of produce. Gardeners ate 6 out of 14 vegetable categories significantly more frequently, and milk products, citrus, sweet foods and drinks less frequently. Except for citrus, the reduced gardener consumption remained significant when other key variables were controlled. Gardening was positively associated with community involvement and life satisfaction.


An estimated one million households are involved annually in community gardening in the U.S. Intuitively, gardening projects would seem to be a potent tool for improving dietary quality, especially vegetable consumption. However, there is little concrete data to test this assumption. Brownrigg's review of the existing information on gardening projects in international settings and in the U.S. shows that little information exists on nutritional, social and economic outcomes, although these have been assumed to be favorable. No systematic or detailed evaluation of a U.S. community gardening project can be found in the literature.

If diet is positively affected by gardening, then improving access to gardening could provide nutrition eductors with an alternative to traditional methods of improving dietary behavior. Where low income is a barrier to following nutritional advice, gardening could possibly be an empowering component of a nutrition intervention strategy.

This report describes a study of the dietary, social and economic correlates of involvement in the Philadelphia Urban Gardening Program. One of the largest gardening projects in the country, this program is sponsored by the Pennsylvania State University Cooperative Extension Service which provides technical assistance, and the Philadelphia Horticultural Society, which provides soil amendments, water and fencing. Nearly 5000 families, including the urban poor, the elderly, and members of diverse ethnic groups, are involved in local projects at 560 gardening sites, many of which are located in vacant lots.

The study addressed the following types of questions:

  1. Dietary: Do gardeners eat more vegetables than non-gardners? If vegetable consumption is increased, are other foods eaten in lesser quantity? Do gardeners use vegetables differently than do controls?
  2. Psycho/social: Why do people garden? How is gardening related to life satisfaction and neighborhood involvement?
  3. Economic: What is the monetary value of the produce grown?
  4. Ethnicity: Are there differences among ethnic groups in the above parameters? Do different ethnic groups obtain different benefits from the gardening experience?


Sample selection. The primary sampling unit was the garden site. The 560 garden sites were stratified by primary ethnic group users, location in Philadelphia. number of plots per site, the length of time the garden had been established (between I and 18 years), and the number of old and new families using the garden site. A random numbers table was used to select a subsample of 64 garden sites. Individual gardeners at these 64 sites were either selected randomly from a garden coordinator's list when available, or were recruited directly at the garden site. The gardeners were interviewed either in their homes or at their garden site. Control subjects were selected on the same ethnic and geographic criteria as were the gardeners. Intent to garden was the third criterion for selecting control subjects so as to minimize gardener/control differences on factors other than vegetable access. However, waiting lists for garden plots from which to make random selections proved to be unavailable. Therefore, friends of the gardeners and potential gardeners identified by the garden coordinators were selected. Data were collected on 144 gardeners and 67 controls: 40 black gardeners and 21 controls, 40 Korean gardeners and 20 controls, 40 white gardeners and 20 controls, and 24 Hispanic gardeners and 6 controls. The full complement of Hispanic subjects was not obtained because of the difficulty of retaining skilled bilingual Hispanic interviewers.

Subjects provided informed consent as approved by the Human Subjects Committee of the Pennsylvania State University. Each subject was paid $20 for his or her participation.

Interviewer selection and training. Interviewers were selected for their ethnicity, linguistic ability in the cases of the Hispanic and Korean subsamples, familiarity with the neighborhoods, and ability to collect dietary data. Interviewers were trained in data collection techniques and were observed while practicing 3-4 interview schedules. Their recorded responses were compared, and more training was provided, if necessary, to improve interviewer reliability.

Dietary information. A non-quantitative food frequency questionnaire, patterned after the National Nutrition Health Examination Survey form, was used to collect information on 23 categories of vegetables, six categories of fruits, and six other categories of foods consumed in the past month. Additional questions were asked about vegetable use in meals. The vegetable categories were later recategorized into 14 groups based on nutrient content. The collection of quantitative dietary data was not feasible, as bilingual nutritionists familiar with intercity populations were not available.

Measures of life satisfaction. Two questions from a compendium of tested measures of social psychological attitudes were used to measure subject mood. Two other questions measured the frequency of positive life events.

Garden plot assessment. A horticulturalist evaluated the potential yield of 160 garden plots drawn from the original subsample of 64 garden sites; 100 were the plots assigned to interviewed gardeners and 60 were chosen randomly. Because recruitment of the gardener subjects was delayed, early harvest yields were not estimated for 100 plots. Garden plots were assessed in July/August and again in September/October 1987. Data on nine gardens was incomplete; thus, 151 plots were characterized by the amounts of different fruits and vegetables grown. As it was not feasible to monitor the actual harvest, each planting was rated for its potential yield on a scale of very good (90% of potential yield) to poor (25% of potential yield).

Economic value of gardening. The market value of inseason vegetables and fruits was collected from retail market outlets in the summer and fall of 1987 and 1988. Expected yields per vegetable and fruit species. and in some cases per variety, were calculated from unpublished 1986-1988 yield data provided by the Rodale Institute and from Jeavons. In the few cases where yield data were unavailable, yields per plant were assumed to be similar to those of the closest species. The economic value of each vegetable and fruit was calculated as the expected yield/plant x assessed number of plants grown x assessed potential yield (0.90 to 0.25) x 1987-1988 dollar market value. These dollar figures were then summed to obtain the market value of the garden.

Time frame. The survey began in June 1987. All data on garden plots were collected by October 1987. Interviews of gardeners and controls began in July 1987 and were completed for all but the Hispanic subjects by November 1987. Hispanic interview data were collected in the last quarter of 1988.

Data analysis. All data were analyzed on the Pennsylvania State University IBM 3090-400E, using The Statistical Package for the Social Sciences. Analysis of variance was used to test for differences between groups, and the Scheffe test was used to test the difference between pairs of ethnic groups. Covariance and multiple regression techniques were used to examine the effects of possible confounding variables on group differences.

Results And Discussion

Comparison of gardeners and controls. Table 1 (Tables not included in this web version) provides means and standard deviations or percentages comparing gardeners, controls, and gardener ethnic groups by age, gender. education and income. The gardeners were older than the controls (p >.001), but there was no significant gender difference between gardeners and controls. Gardeners had a lower mean education by category compared with the controls (p >.001). Income by category was not significantly different between gardeners and controls, though gardeners tended to have lower incomes. Overall, the Korean and black gardeners were older than the white or Hispanic gardeners, and Korean gardeners were most likely to be male. By observation, whites had strikingly higher incomes and education than the other gardener groups.

Gardeners were longer-time Philadelphia residents than tbe non-gardeners (26.3 + /- 19.7 years vs. 18.1 + /- 13.4 years; p <.05) and had lived in their neighborhoods significantly longer (15.2 t 14.2 years vs. 10.4 t 8.9 years; p > .05). Consistent with their age. fewer gardeners reported working full time (20. 1% vs. 35.8%) and more reported being retired (21.5% vs. 1.5%). Almost equal percentages of gardeners and controls reported not working at the present time (39.6% vs. 38.8%), primarily because Korean gardeners of retirement age consistently reported their work status as not working at the present time.

Description of gardeners. Of the sample of 144 gardeners, 77.8% were cultivating a plot at a community garden and 20.8% were gardening in a vacant lot or space near their home. Fifty-one percent had never gardened before the 1987 season. Gardeners had maintained their garden plot a mean of 4.1 + /- 3.0 years. with a range of 1-13 years. A mean of 11.7 + /- 11.3 hours per week were spent in the garden; 5.6 + /- 7.1 of these hours in "heavier" work like hoeing. digging. planting or pulling weeds.

On the average gardeners ate their produce fresh from the garden for 5.0 + /- 3.1 months of the year; 9 7% harvested vegetables for 12 months a year. Food preservation was practiced by 62%. Thirty-five percent of the gardeners had access to a separate freezer where they froze an average of 17.4 + /- 27.5 pints of produce. The freezer compartment of a refrigerator was used by 47.2% of the gardeners to freeze a mean of 13.0 + /- 20.0 pints of produce. Thirty-six percent of the gardeners canned a mean of 16.0 + /- 25.3 pints of produce. Twenty-nine percent dried a mean of 4.4 + /- 15.3 pint equivalents. Home preserved food was consumed for an average of 7.2 + /- 4.2 months per year.

Table 2 shows with whom and how often the gardeners shared their produce. Gardeners were most likely to share their produce with their neighbors and relatives, often on a weekly basis. More than 40% of the gardeners had shared their produce with a church or community organization.

Gardeners were asked in an open-ended question the reasons they gardened and which was the most important reason. Their responses to the latter question were grouped into categories. Recreation (21%), mental health (19%), physical health and exercise (17%), produce quality and nutrition (14%), spiritual reasons, including contact with nature (10%), self expression/self-fulfillment (7%), and cost and convenience (7%) accounted for 95% of the responses. Even in this predominantly inner city, low income sample the perceived monetary benefits of gardening were outweighed by the perceived positive effects of life quality and health. Nearly 53% of thc Korean gardeners named physical health and exercise as primary reasons for gardening whereas no whites gave these reasons as primary. Twenty percent of the black and the white gardeners were primarily motivated by the nutritional benefits of gardening, whereas few Hispanics and Koreans gave this reason.

Tbe effect of gardening on diet. Tables 3 and 4 report the mean number of times per month that gardeners, controls and gardener groups reported consuming vegetables, fruits and other foods. Gardeners consumed the following vegetables significantly more frequently than did controls: cole crops (cabbage, broccoli, brussels sprouts, kale, cauliflower, pak choi and a variety. of Chinese vegetables), okra and eggplant, sweet and hot peppers, summer squash (zucchini, bitter melon and chayote), tomatoes, and herbs. Other than iceberg lettuce, celery and fresh salad greens, the gardeners' vegetable consumption frequency was always slightly'higher than the controls.' White gardeners had consumption frequency significantly higher than at least one other ethnic group for eight of the vegetable categories. Korean gardeners had a low consumption frequency for eight of the vegetable categories, in part because the categorization used does not reflect Asian eating patterns.

Non-gardeners consumed more fruits than the gardeners, specifically in the category of citrus fruits and juices. White gardeners consumed more fruits that other groups. Meat, poultry, fish and egg consumption was similar between gardeners and controls. Korean gardeners consumed animal flesh less frequently than did the other gardener groups. Gardeners consumed less milk products (fluid milk, cheese. ice cream, buttemilk, cottage cheese). sweets (cakes. pies. sweet rolls, doughnuts. candy, and chocolate). and sweet drinks soda, Kool-Aid and punch than did the controls. Korean and black gardeners consumed fewer milk products than did the white or Hispanic gardeners, perhaps due to intolerance to the lactose in milk.

The Nationwide Food Consumption Survey data suggest that the consumption of dark green and deep yellow vegetables increases with age. Controlling for age, the differences shown in Table 3 between gardener and non-gardener vegetable consumption remained significant, except for the pepper category. Controlling for education increased the significance of the difference between gardener and control consumption of cole crops.

Age and income, but not education, were significantly related to milk consumption frequency. Gardening remained a significant predictor of milk consumption after controlling for age and income (r = - 0.225, partial r = - 0.182, p > .01). Controlling for age and education did not affect the significance of the difference in gardener and control consumption of sweet drinks (r = -0.271, partial r = -0.236, p > .01) and only slightly lowered the significance of the difference in consumption of sweet foods (r = 0.264, partial r -0.171, p > 05). Age explained the difference between gardeners and controls in the frequency of consumption of both total and citrus fruits.

Gardeners and non-gardeners reported similar vegetable eating patterns. There were no differences in how often they ate vegetables cooked as a side dish, in stews and casseroles, raw in salads, or between meals for snacks. However, gardeners were more likely than non-gardeners to eat vegetables in meatless meals (p > .05). White gardeners were significantly more likely than other groups to eat vegetables raw in salads, and more likely than blacks to eat vegetables between meals and in meatless meals.

Community perceptions and participation. Gardeners were more likely than controls to regard their neighbors as friendly, but were no more likely to regard their neighbors as helpful. Gardeners and controls were in close agreement about the conditions in their neighborhoods with regard to vandalism and to cleanliness of public areas and private property.

Gardeners were more likely than controls (p > .001) to participate in food distribution projects, neighborhood cleanups or beautification projects, and neighborhood barbecues and social events. Controlling for the number of years in the neighborhood slightly reduced the significance of this relationship for participation in cleanups, but had no effect on gardeners increased involvement in food distribution and social events. Korean gardeners were most likely to distribute food, and black gardeners were more likely than whites or Hispanics to participate in neighborhood cleanups.

Life satisfaction. Table 5 presents the responses to the questions on psychosocial wellbeing and frequency of meaningful life events. Gardeners gave a significantly more positive response than did the controls to each question. There were no significant differences among the gardener groups. Though causality cannot be inferred, it appears that those who are involved in gardening find life more satisfying and feel they have more positive things happening in their lives than those who are not.

Evaluation of the garden plots. Garden plots varied tremendously in quality of care, diversity of plantings and gross value. The mean quality factor of the garden plantings was .77 +/- 0.13. Thus, an average planting yielded 77% of its potential. Gardens contained a mean of 8 1 +/- 5.1 species of plants, with a range of 1 to 29 species.

The mean economic value of the 151 assessed garden plots was $160 +/- $178 for one year, with a range of $2 to $1134. This is similar to the median yield value category of $101 to $250 for community vegetable production reported by the National Gardening Association survey of community gardens. Using these value categories, 49.7% of the Philadelphia urban garden plots yielded produce worth >$100, 29.2% had a yield worth between $101 and $250, 15.1% yielded between $251 and $500, and 6% yielded produce worth >$500. The comparable figures from the National Community Gardening Survey were 44%, 26%, 23% and 7%, respectively. Most likely the average value of the Philadelphia garden plot assessment was underestimated, as neither early planting nor the value of flowers were assessed.

Gardeners spent an average of $47 per person on plants, seeds, fertilizers and pesticides, tools, soil, soil improvements, and fencing. This is close to the $41 estimated for all gardeners nationally. The net value of the garden plots after expenses was $113.

Differences in gardening benefits among ethnic groups. Though gardeners were divided into ethnic groups for the purposes of this study, gardeners at specific sites tended to reflect the ethnic mixture of the community, however, some generalizations can be made. The older community gardens in predominantly black neighborhoods often served as social centers for the community, green oases in the hot Philadelphia summers. Smaller and newer gardens in Hispanic areas were often sources of neighborhood pride. Gardens helped reinforce social cohesiveness among the Koreans, who frequently worked together on their garden plots. Whites tended to garden in large sites distant from their neighborhoods, thus their gardening did not strengthen neighborhood relations.

White and black gardeners tended to eat vegetables more frequently than did the Hispanic or Korean gardeners. Interest in nurtrition and nutritional spinoffs of gardening appeared to be greater for the former groups.


The major findings of this study are that gardening is related to an increased frequency of vegetable consumption and to the reduced frequency of milk product consumption. However, the lack of a completely random sample selection limits the interpretation of these data. Gardening remained a significant negative predictor of milk product consumption even when significant predictors such as age and income were controlled. Gardeners also ate sweet foods and drinks less frequently than did the controls. Thus. it appears that gardeners do eat some foods less frequently when vegetable consumption frequency increases. However, it cannot be inferred from this non-quantitative food frequency data that the diet of the gardeners suffered from lack of calcium. It is possible that cole crops helped provide some of the calcium that the milk products would have provided for the gardeners. The finding that gardeners consume milk products less frequently indicates that nutrition advice should be dispensed along with horticultural advice for gardeners. Perhaps gardeners could be provided with produce-utilization recipes that incorporate milk products or vegetables high in calcium.

Inner city residents may have difficulty obtaining fresh vegetables due to the cost, the exodus of supermarkets, and a lack of adequate transportation. Using the criteria of Rody (11), this study provides evidence that gardening access in the inner city is an empowering nutrition strategy that overcomes many of the barriers to increasing vegetable consumption. Gardeners are able to use their own resources to meet part of their food needs in the manner they deem appropriate, Gardeners have greater control over the variety, quality, and quantity of the produce they consume, Finally, gardening appears to facilitate community' self-help. Gardeners were more active than non-gardeners in community projects, and shared their vegetable wealth with family, friends, passers-by, and church food pantries, thereby becoming nutrition change agents in their own right.

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Revised February 18, 1997

Published by City Farmer
Canada's Office of Urban Agriculture