Food Source Information Swiss Chard

The colorful, leafy green known as Swiss chard is actually a beet that was developed specifically for its edible stems and leaves, which are often used in recipes as a substitute for spinach. Though it closely resembles spinach, and is a member of the same plant family, Amaranthaceae, Swiss chard is often compared to kale. Swiss chard is a biennial crop, available year-round and is unique in that it does well in both cool and hot temperatures. It can be eaten either cooked or raw depending on the consumer’s preference. Like many vegetables in the leafy green family, Swiss chard is susceptible to foodborne pathogens if Good Agricultural Practices (GAPs) are not followed. Because they support a medium for pathogen growth, these potentially hazardous vegetables are safer when kept at temperatures of 41° F or lower.

Swiss chard’s history can be traced to Sicily but, over the years, it has gained popularity amongst Mediterranean chefs and across Europe. Chard’s name was changed to “Swiss chard” as producers sought to distinguish it from French chard. By the 19^th century, the new name had taken hold and was being printed in seed catalogs. Until the 1850’s, Swiss chard was categorized as a specialty plant produced mainly for European markets; however, following the American Civil War, the United States began increasing cultivation of the crop. The non-native species of North America became domesticated from the wild variety of the Mediterranean region. Originally, the young plant’s leaves were added to salads; however, in the 19^th century, chefs began separating the leaves from the mid rib for cooking, which helps to remove the bitter flavor.

Leafy greens are highly perishable and considered to be one of the riskiest foods on the market. The first major foodborne illness case involving leafy greens was a 2006 spinach outbreak. Since then, the Centers for Disease Control and Prevention (CDC) and the Food and Drug Administration (FDA) have brought awareness to the potential contamination of raw, fresh commodities being packaged and sold. The pathogens of most concern for contamination of leafy greens like Swiss chard are E. coli, Salmonella, and Listeria.

A recall in 2016 was the result of contaminated Swiss chard pesto produced by One Heart organics brand in Canada. The pathogen associated with the recall was Clostridium botulinum, which was discovered during a routine inspection by the Food Safety Inspection Service.

An outbreak involving Swiss chard resulted in a recall in November of 2010. Salmonella was found to have possibly contaminated the Little Bear Brand of leafy greens, which included both rainbow chard and green chard. The manufacturing company in Edinburg, TX, was identified as J & D produce.

There was a multi-state outbreak involving prepackaged leafy greens manufactured by State Garden Produce Company operating in Chelsea, Massachusetts in 2012. The CDC and FDA covered the investigation and found the Shiga-producing toxin E. coli O157:H7 had infected 33 people across 5 states. Those infected ranged in age from 4 to 66. Two cases of kidney failure were reported as a result of hemolytic uremic syndrome (HUS), and a total of 13 people were hospitalized during the outbreak. Those who fell ill reported eating a variety of packaged leafy greens and a large portion had eaten organic spring mix and spinach, but the specific type of lettuce responsible for the outbreak was never identified.

In 2021, there was a recall due to an E.coli O157:H7 outbreak linked to packaged salads sourced from California and Arizona. Simple Truth Organic Power Greens and Nature’s Basket Organic Power Greens recalled all packaged salads that included spinach, mizuna, kale, and chard. There were 10 illnesses, 4 hospitalizations, and no deaths.

Swiss chard’s bulky leaves are highly perishable and do not fare well in large commercial production. However, they can be readily found at farmers’ markets, where the crop is marketed directly to consumers. The bulk of Swiss chard produced is sold either as bunched leaves or as young leaves sent to be processed into salad mixes. The major appeal of Swiss chard is the vibrant color of its stalks and its ability to be eaten raw or cooked like spinach.

Pre-Harvest

Swiss chard is like other leafy greens which prefer a well-drained, fertile loom soil with a healthy amount of organic matter incorporated. However, Swiss chard will grow well regardless of soil type, temperature, or day length. Chard can be either direct seeded 0.5 to 1.0 inches deep, or transplanted when the seedlings have 4 to 6 leaves. Germination occurs best above 40° F. The plant flourishes in full sun, which is about 8 to 10 hours a day, and is generally planted in wide rows spaced 6 inches apart. Once the crop begins to grow, thinning is advisable. Swiss chard fares best in soil that has a pH of 6.5 to 7.5 and it thrives during spring and fall months when cool night temperatures range from 60° to 75° F. Hot summer temperatures diminish the quality of the crop, reduce growth, and contribute to bitter taste. The best method of irrigation for Swiss chard is about 10 to 15 inches throughout the season. Overhead sprinklers are a common method for watering these crops; however, Swiss chard is susceptible to foliar disease and does better with other types of irrigation. Ensuring the plant has consistent moisture is important, especially during development; a fluctuating water consistency can result in an inadequate uniformity and taste. Ultimately, the location where the Swiss chard is being grown will determine the amount of water needed, but mulching can be beneficial for retaining an even moisture content. Harvesting the outer leaves first allows the plant to continue to produce throughout the season by avoiding damage to the terminal bud at the center of the plant. The outer leaves should be harvested while they are still young and tender, when they are anywhere from 8 to 12 inches long. Swiss chard is typically harvested by hand and yields approximately 150 hundred weight per acre. A 10-foot row of Swiss chard plants can produce up to 12 pounds for sale. The plant continues to produce until it begins to bolt or flower.

Post-Harvest

Chard can be stored for one to two weeks, as long as it is refrigerated at 40° F or below. Chard should be handled much like spinach and benefits from precooling by a vacuum cooler before being packed with fresh ice to preserve its quality and freshness. It is then typically stored in a 32-pound crate with holes to maximize the yield.

As is the case with other leafy greens, Swiss chard is a raw, fresh, highly perishable product. It is important, therefore, to follow safety protocols throughout the production process in order to prevent contamination. Leafy greens are categorized as potentially hazardous foods because they are highly vulnerable to pathogenic contamination and must be kept at temperatures of 41° F or less to be safe for consumption. If leafy greens are not kept at these recommended temperatures, pathogens can potentially survive and counteract any prewashing steps previously taken. Leafy greens are particularly susceptible to pathogens because the pH, water activity, available moisture, and nutrients from the greens provide an excellent habitat for pathogens to thrive. It is best to prevent contamination before it occurs by sanitizing all tools used in the field and by cleaning the greens before they are sent to market.

Good Agricultural Practices (GAPs) should be adhered to at all times. These practices include taking basic steps to prevent contamination as well as following proper methods to eliminate microbial contamination once it occurs. Leafy greens can become contaminated at any time during the harvesting, washing, cutting, packaging, or shipping processes. The most common sources of contamination are Salmonella, E. coli and sometimes Listeria.

As a member of the leafy greens category of produce Swiss chard is included in California’s Leafy Greens Marketing Agreement (LGMA), which has helped address safety protocols for leafy greens by finding the best strategies for preventing contamination and by identifying a set of common practices producers can follow.

The greens covered by the LGMA include: arugula, baby leaf lettuce, spring mix, butter lettuce, cabbage (red, green, and savoy), chard, kale, endive, escarole, green leaf lettuce, iceberg lettuce, red leaf lettuce, romaine lettuce, and spinach.

Consumers should use care when handling and preparing leafy greens in order to avoid cross-contamination in the kitchen. The best way to clean leafy greens is by washing them in cold water. If there is extra soil on the leaves or stems, fill an empty bowl with cold water and let them soak briefly, one to two minutes. Use a dry, unused towel to blot the greens.

Swiss chard is a favorite leafy green of consumers because of its red, white, orange, pink, and purple colors, its nutritional benefits, and its versatility. Chard has a mild, sweet earthy taste with some bitterness and is often found bunched at farmer’s markets or on store shelves. Chard is a unique green because both the leaf and the colorful stalk can be cooked and enjoyed, unlike kale, where the petiole is usually discarded prior to consumption. The vegetable loses its bitter flavor and takes on a more refined taste when it is cooked. Swiss chard is typically enjoyed fresh, but it can be frozen, canned, or dried as well.

Information on how to properly store Swiss chard and other leafy greens can be found at Food Keeper App.

Swiss chard is similar to other leafy greens in that it is loaded with vitamins and minerals, making it a nutritious addition to a balanced diet. It contains vitamins A, C, and K in addition to minerals, phytonutrients, and fiber. Phytonutrients have been known to protect against cataracts and macular degeneration, vitamin A helps to maintain healthy skin, vitamin C helps to boost the immune system, and calcium improves bone health. Although chard has a higher sodium content than other vegetables of its kind, it also has high levels of the minerals iron, magnesium, phosphorus, potassium, and calcium.

1. American Cookery & A History of Its Ingredients [Internet]. [cited 2017 Jul 31].
2. Chard – Vegetable Directory – Watch Your Garden Grow – University of Illinois Extension [Internet]. [cited 2017 Jul 31].
3. Commercial Production and Management of Cabbage and Leafy Greens | UGA Cooperative Extension [Internet]. [cited 2017 Jul 31].
4. Davidson, Gordon R. B Annemarie L, Ryser, Elliot T. Efficacy of Commercial Produce Sanitizers against Nontoxigenic Escherichia coli O157:H7 during Processing of Iceberg Lettuce in a Pilot-Scale Leafy Green Processing Line. Journal of Food Protection [Internet]. 2013 [cited 2017 Jul 27];76(11):1838–45.
5. Drost, Dan. Swiss chard in the garden. 2010 [cited 2017 Jul 31]
6. Explore Cornell – Home Gardening – Vegetable Growing Guides – Growing Guide [Internet]. [cited 2017 Jul 31].
7. Food Code Fact Sheet #11: Cut Leafy Greens| Oregon Department of Agriculture, Food Safety Division [Internet].
8. From Garden to Table: Leafy Greens! — Publications [Internet]. [cited 2017 Jul 31].
9. Greens| Mississippi Extension Service [Internet]. [cited 2017 Jul 31].
10. Home Garden Swiss Chard | UGA Cooperative Extension [Internet]. [cited 2017 Jul 31].
11. HS1279/HS1279: Leafy Greens in Hydroponics and Protected Culture for Florida [Internet]. [cited 2017 Jul 31].
12. J&D Recall Expands to 18 Other Vegetables, Greens | Food Safety News [Internet]. [cited 2017 Jul 31].
13. Joe Masabni. Swiss Chard [Internet]. Texas AgriLife Extension Service, Department of Horticulture.
14. Kale | Produce Market Guide [Internet]. [cited 2017 Jul 31].
15. Leafy Greens & Mixed Greens [Internet]. [cited 2017 Jul 31].
16. Lee Taylor GV, Linda Whitlock MW. Smart Gardening: How to grow greens [Internet]. Michigan State University Extension.
17. Mishra, Abhinav G Miao, Buchanan, Robert L. S Donald W, Pradhan, Abani K. Development of growth and survival models for Salmonella and Listeria monocytogenes during non-isothermal time-temperature profiles in leafy greens. Food Control [Internet]. 2017 [cited 2017 Jul 31];71:32–41.
18. Mishra, Abhinav G Miao, Buchanan, Robert L. S Donald W, Pradhan, Abani K. Prediction of Escherichia coli O157:H7, Salmonella, and Listeria monocytogenes Growth in Leafy Greens without Temperature Control. Journal of Food Protection [Internet]. 2017 [cited 2017 Jul 27];80(1):68–73.
19. Multistate Outbreak of Shiga Toxin-producing Escherichia coli O157:H7 Infections Linked to Organic Spinach and Spring Mix Blend (Final Update) | Multistate Outbreak Linked to Organic Spinach and Spring Mix Blend | E. coli | CDC [Internet]. [cited 2017 Jul 27].
20. Program Information Manual Retail Food Protection: Recommendations for the Temperature Control of Cut Leafy Greens during Storage and Display in Retail Food Establishments [Internet]. 2010.
21. Rainbow Swiss Chard Information, Recipes, and Facts [Internet]. [cited 2017 Aug 3].
22. Schrader, Wayne L. M Keith S. Beet and Swiss Chard Production in California| University of California [Internet].
23. Swiss Chard – Master Gardener Program [Internet]. [cited 2017 Aug 3].
24. Swiss chard vs Rainbow chard: Is There a Difference? | University of Maryland Dining Services [Internet]. [cited 2017 Aug 3].
25. University of Minnesota Extension. Growing leafy greens in Minnesota home gardens: Vegetables: Yard and Garden [Internet].
26. USDA ERS – The California Leafy Greens Industry Provides an Example of an Established Food Safety System [Internet]. [cited 2017 Jul 27].
27. Vegetable Profiles: Swiss Chard| University of Maryland Extension [Internet]. [cited 2017 Jul 31].