Chapters 5.59

5.59 -Tomatillos (Physalis)as a Potential Crop for Smallholder Farmers

Naomi Haworth , University of Guelph, Canada

Suggested citation for this chapter.

Haworth,N. (2022) Tomatillos (Physalis)as a Potential Crop for Smallholder Farmers, In Farmpedia, The Encyclopedia for Small Scale Farmers. Editor, M.N. Raizada, University of Guelph, Canada. http://www.farmpedia.org

Introduction to Tomatillos

Tomatillos or husk tomatoes (Physalis philadelphica), produce tart green, or sometimes purple fruits that are surrounded by a thin, papery husk. They are members of the nightshade family and originate in Mesoamerica, where their use dates as far back as pre-Columbian times (Hernández Bermejo & León, 1994; Kindscher et al., 2012). Mexico, as the dominant producer of tomatillos, currently grows 70 of the total 90 Physalis species, and agro-industries there are estimated to process 600 tonnes of fruit each year (Hernández Bermejo & León, 1994; Vargas-Ponce et al., 2016). Typically, the fruits are used in salsas, sauces, and stews, but tomatillos can also be eaten raw or cooked using other methods (Kindscher et al., 2012). In addition to culinary use, tomatillos have promising benefits for the medical field. Preliminary research has shown the leaves to have chemicals called withanolides, which exhibit antimicrobial, anti-inflammatory, and anti-cancer activities (Kindscher et al., 2012). Unfortunately, the foliage of tomatillos cannot be used for livestock feed, as these chemicals are poisonous to animals (Kindscher et al., 2012). Instead, foliage can be composted to improve soil organic matter. Similar to tomatoes, tomatillo varieties produce many different fruit sizes, some just small berries, others reaching up to 5 cm in diameter (Hernández Bermejo & León, 1994).

Growing Methods and Agricultural Benefits

Tomatillos, which are typically cultivated by seed in fields, prefer fertile, well-drained soil, with a slightly acidic pH between 6.0 and 6.8 (Kaiser & Ernst, 2017; Ontario Ministry of Agriculture, Food, & Rural Affairs [OMAFRA], 2012; Ramos-López et al., 2017). If soils are too acidic (low pH), applying limestone products can help to increase soil pH (decrease acidity) (Clemson Cooperative Extension, 2012). Alternatively, if soils are too alkaline (high pH), applications of sulfur can reduce pH (Clemson Cooperative Extension, 2012). Tomatillos prefer fertile, sandy, well-draining conditions, not clay soil (Kaiser & Ernst, 2017). However, the addition of manure, compost, and other organic matter can help to improve soil quality over time, thus making conditions more favourable for tomatillos.

They are cold-sensitive below 15 °C (59 °F), so tomatillos grow best in warm climates with full sun and average temperatures between 24 °C and 32 °C (75 °F to 90 °F) (OMAFRA, 2012). Tomatillos are bushy and spreading plants that can grow up to 3 ft or 4 ft tall (91.5 cm to 122 cm) with an equal width (Everhart et al., 2003). They thrive in disturbed, weedy habitats (Kindscher et al., 2012). Staking is recommended, though not mandatory, to reduce husk rot and ease the harvesting process, but this requires extra resources and labor (Kaiser & Ernst, 2017). Instead, plants can be left to trail and spread on the ground, which helps to protect soil, prevent evaporation, and suppress weeds (Kindscher et al., 2012). Smallholder women farmers can spend the majority of their on-farm time pulling weeds by hand manually, so the natural weed supressing capabilities of tomatillos can reduce weeding drudgery for women (Giannessi, 2009).

In areas with long growing seasons, tomatillos can be direct-seeded 35 cm to 60 cm (13.7 in to 23.6 in) apart in rows spaced 40 cm to 75 cm (15.7 in to 29.5 in) apart or propagated vegetatively from a stem cutting of an existing plant (OMAFRA, 2012). In shorter growing season areas, following the same spacing guidelines, seedlings can be transplanted once the soil has reached a minimum of 15 °C (59 °F) (OMAFRA, 2012). Once planted, tomatillos typically mature in 80 to 100 days and require very little maintenance (OMAFRA, 2012).

Tomatillos are relatively drought-tolerant, requiring only 2 cm to 5 cm (0.8 in to 1.9 in) of water per week (Pedersen & Drost, 2020). They are most commonly grown on irrigated lands but can withstand dry conditions by absorbing residual humidity and by taking up water from sporadic, heavy storms (Hernández Bermejo & León, 1994). Rainwater harvesting, mulching, and drip irrigation systems can be implemented in areas with infrequent rainfall, though this can be costly and labor-intensive.

Since tomatillos are relatively light feeders, the need for chemical fertilizers is low, and they make excellent intercrops, commonly grown in companion with corn, beans, and gourds (Hernández Bermejo & León, 1994). As an intercrop, tomatillos have the potential to suppress weeds. Large scale operations can apply chemical fertilizers if needed with a dose of nitrogen typically between 120 kg to 240 kg per hectare, and 60 kg to 150 kg of phosphorus for the same area (Hernández Bermejo & León, 1994). For smallholder farmers, a side-dress of 1 tablespoon per plant of high nitrogen fertilizer is suggested four to eight weeks after planting (Pedersen & Drost, 2020). Excessive fertilization can delay fruit set and maturity by causing excess leaf growth, so soil tests are recommended beforehand, as fertilizer may not be necessary (Pedersen & Drost, 2020).

Tomatillos are indeterminate, meaning that the flowers and fruit will continue to be produced until the plant is killed (Everhart et al., 2003). Tomatillos should be harvested by hand to protect the delicate husk and fruit (OMAFRA, 2012). After harvesting, tomatillos can be peeled from their husk, washed of their sticky residue, and eaten raw or prepared in numerous other ways (Pedersen & Drost, 2020). If not used immediately after harvest, tomatillos should be stored with their husks on, ideally in a cool, high humidity area (OMAFRA, 2012). If in optimal conditions, tomatillos can last for up to three weeks (OMAFRA, 2012).

Three main pests prey on tomatillos. Frankliniella occidentalis and Thrips tabaci both primarily affect flower development by feeding on tomatillos during immature stages, while the larvae of Heliothis subflexa feeds on the developing fruit (Bautista-Martínez et al., 2015; Palomo et al., 2015). Not only do these pests feed on Physalis species, but they can also carry and transmit harmful viruses (Palomo et al., 2015). Providing the appropriate nutrient and water requirements is the best method to protect crops from various pest and pathogen attacks, as nutrient deficiencies and extreme water stress put tomatillos at an increased risk for outbreaks (Palomo et al., 2015). As well, tomatillos contain chemicals called withanolides that have insect-antifeedant properties, thus acting as natural pesticides (Kindscher et al., 2012). Further development to increase the concentration of withanolides and to improve the distribution of these varieties would be of benefit for farmers because of the reduced need for chemical pesticides.

Uses and Nutritional Benefits

Historically, tomatillos have been used as medicines for thousands of years. The roots of P. longifolia, P. virginiana, and P. pumila were used by the Omaha, Ponca, and Winnebago indigenous peoples of the Americas to treat headaches, stomach troubles, and wounds (Kindscher et al., 2012). The dried leaves of P. heterophylla were used by the Iroquois indigenous people to treat sores and as a tea to alleviate stomach pain (Kindscher et al., 2012). In addition to these time-tested medical benefits, tomatillos also show antimicrobial, anti-inflammatory, and anti-cancer properties, as previously mentioned, due to the presence of withanolides (Kindscher et al., 2012). More research is needed, but because of their chemical properties, tomatillos have a promising future in medicine and potentially as an income source for farmers.

Not just useful for medicine, tomatillos also have nutritional benefits, as they possess many important macronutrient and micronutrient components. Though no cultivar information was given, the USDA reports that per 100 g of tomatillo, the caloric value is 31.45 kcal, of which 0.75-1.06% is protein, 1.12-2.10% is fat, and 0.085-0.68% is dietary fiber, with a carbohydrate content of 4.36% by weight (Shenstone et al., 2020). In addition to macronutrients, tomatillos contain vitamin A and folate, which are commonly deficient micronutrients in developing nations, as well as thiamine, an essential amino acid. Per 100 g, tomatillos contain 11.7 mg of immune-boosting vitamin C (7% of the adult recommended daily value), 114 IU of vitamin A, 7 μg of folate, and 0.044 mg of thiamine, among other micronutrients (Shenstone et al., 2020)

Because of their fresh, tart taste and culinary versatility, tomatillos can replace or substitute for other ingredients in salads, sauces, salsas, and stews. As well, since tomatillos sweeten as they mature, the sweeter fruits could be an easy way for children to obtain important micronutrients (Kaiser & Ernst, 2017). Since they are so versatile and can be eaten and cooked in numerous ways, they are an excellent addition to any diet to help populations achieve proper macronutrient and micronutrient requirements.

Economic Analysis

After an initial purchase, seeds can be saved and used in the next growing season, which eliminates yearly purchasing (Hernández Bermejo & León, 1994). Additionally, if local average rainfall does not meet minimum requirements, an irrigation system, though costly, is a worthwhile investment for all crops. The main cost of tomatillos, which varies by location, comes from labor requirements, as hand-harvesting is recommended (OMAFRA, 2012). Staking plants, though not mandatory, will also cost money for materials, time, and labor.

Tomatillos are low maintenance crops because of their low water and nutrient needs. Using compost or manure to increase soil organic matter and mulching to retain moisture and suppress weeds are low-cost practices that can help to improve soil quality and, by extension, plant yields. Since tomatillos are indeterminate, multiple harvests spread throughout the season can be made from the same plant (OMAFRA, 2012). Even in poor conditions, tomatillos can produce high yields, as an individual plant can produce anywhere from 64 to 200 fruits in a single season (Kaiser & Ernst, 2017). An average yield per one acre of land is 8.16 metric tons, or 2.5 lbs of fruit per plant (Masabni, 2017). In 2019, raw tomatillos were sold in Mexican supermarkets for just MX$ 23.90 (US$ 1.09) per kilogram (Hogewoning, 2020). If an average yield is 8160 kg per acre, and the average kilo sells for US$ 1.09, then the value of one acre of tomatillos roughly US$ 8894 minus inputs, land and labor costs.. Commodity prices are low in Mexico because tomatillos are native and abundant in the area, but the fruit could have more value in other locations.

The cost and potential profit of growing tomatillos will depend on the area, but in general, profitability is greater when selling at local markets compared to wholesale export (Kaiser & Ernst, 2017). To increase profits, in addition to raw fruits, farmers can sell homemade tomatillo sauces that are adapted to local tastes. These sauces could also be sold to the local tourist industry, especially people from Latin America, as they may be interested to know how an ingredient that is so familiar to them is being used in different areas of the world. Tomatillos can also be pickled as another value addition. Making sauces and pickling tomatillos not only increases profits, but it helps to solve the storage constraints caused by a lack of refrigeration in some areas. These value additions would require resources such as containers and jars. Selling tomatillo sauces, as well as raw and pickled fruits, means that tomatillos in home gardens have potential as a source of income for smallholder women farmers.

Constraints and Disadvantages

Since tomatillos require a minimum of 2 cm (0.8 in) of water per week, they are not suitable for growing in hyper-arid, extreme drought conditions unless adequate rainwater harvesting systems are in place to catch rainfall from sparse, heavy storms (Pedersen & Drost, 2020). Additionally, tomatillos are self-incompatible, requiring more than one plant for fertilization, and extreme heat can result in poor fruit set, so moderate climates are preferred (Mulato-Brito et al., 2007; OMAFRA, 2012). Thrips are a common pest for tomatillos, but proper plant care can reduce susceptibility (Palomo et al., 2015). Lastly, ideal storage conditions require cool temperatures, which can be a challenge for many farmers living in hot climates without electricity. Instead, tomatillos can be left to ripen on the plant and picked as needed or can be pickled or made into sauces to extend shelf life and eliminate storage concerns. Given the storage constraints, a local market or buyer must be established prior to adopting tomatillos as a cash crop.

Conclusions

Despite the initial cost of seeds and irrigation and the labor requirements, tomatillos would be a valuable crop to introduce to smallholder farmers in developing nations because of their drought and pest resistance, minimal water and nutrient requirements, culinary versatility, nutritional importance, income-earning abilities, and potential in the medical field. However, further research and development is needed, focusing on improving their drought tolerant and pest resistant traits to bring tomatillos to their full potential. Lack of refrigeration on smallholder farms means that linkages to nearby markets is critical.

Useful Resources

https://www.youtube.com/watch?v=aQAdblbaQKM Short video describing the benefits of growing tomatillos.

https://www.thespruce.com/growing-tomatillos-in-the-vegetable-garden-1403467 Lists the plant requirements and describes planting practices, proper care, harvesting methods, and propagation techniques.

https://www.thekitchn.com/15-delicious-ways-to-use-tomatillos-any-time-of-day-recipes-from-the-kitchn-206915 Provides links to 20 different recipes using tomatillos to help with introduction and integration of tomatillos into a diet.

https://www.cropsreview.com/row-planting.html Provides information on row planting and its benefits.

https://www.youtube.com/watch?v=fGq-ZvP3pHU Video showing the process of cultivating tomatillos from starting seeds to harvesting.

https://www.youtube.com/watch?v=vbQCIMJebac Video showing a planting technique to help increase root growth for tomatoes and tomatillos.

https://www.youtube.com/watch?v=DLsHqGgOLzc

Video showing tomatillos grown on a small-scale farm and demonstrating when the fruit is ready for harvest.

https://www.goodhousekeeping.com/home/gardening/a20705723/your-guide-to-growing-the-biggest-tomatillos-north-of-mexico/ Article describing planting practices, care and maintenance, and cooking techniques and ideas.

https://plantix.net/en/blog/affordable-diy-drip-irrigation-systems Shows various methods to create low-cost irrigation systems.

https://morningchores.com/rainwater-harvesting/ Depicts various ideas for rainwater catchment systems.

References

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2. Clemson Cooperative Extension. (2012, October 20). Changing the pH of your soil. a. Home & Garden Information Center. b. https://hgic.clemson.edu/factsheet/changing-the-ph-of-your- c. soil/#:~:text=To%20make%20soils%20less%20acidic,adjust%20the%20soil%2 d. 0pH%20value.

3. Everhart, E., Haynes, C., & Jauron, R. (2003, April). Tomatillos. Iowa State University Extension Office Horticulture Guide. https://store.extension.iastate.edu/Product/Tomatillos-PDF

4. Gianessi, L. (2009). Solving Africa’s weed problem: Increasing crop production & a. improving the lives of women. Crop Protection Research Institute. b. https://croplifefoundation.files.wordpress.com/2012/05/solving-africas-weed-problem-report1.pdf

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7. Kaiser, C., & Ernst, M. (2017, March). Tomatillo. University of Kentucky College of Agriculture, Food, and Environment Cooperative Extension Service. a. https://www.uky.edu/ccd/sites/www.uky.edu.ccd/files/tomatillo.pdf

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11. Ontario Ministry of Agriculture, Food, & Rural Affairs. (2012, October 17). Tomatillo. Specialty Crop Opportunities. Retrieved from http://www.omafra.gov.on.ca/CropOp/en/spec_veg/fruit_veg/toma.html

12. Palomo, L., Martinez, N., Johansen-Naime, R., Napoles, J., Leon, O., Arroyo, H., & Graziano, J. (2015). Population fluctuations of thrips (Thysanoptera) and their relationship to the phenology of vegetable crops in the central region of Mexico. The Florida Entomologist, 98(2), 430-438. https://doi.org/10.1653/024.098.0206

13. Pedersen, K., & Drost, D. (2020, April). Tomatillos in the garden. Utah State University a. Extension. https://digitalcommons.usu.edu/extension_curall/1631/

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