Introduction

Wild edible plants (WEPs) are non-cultivated plant species harvested to be consumed as food or drink [1], also known as wild food plants (WFPs). WEPs are not domesticated, but can be managed, such as by transplanting from forest to agricultural systems for easier access [2]. We use the term “wild” to refer to those plants that grow without being cultivated, mostly including native species growing in their natural habitat, but sometimes managed, as well as introduced species that have become naturalized or escaped cultivars which were viewed as wild.

Throughout history, humans have depended on WEPs, along with diverse wild animals and their products, for nutrients and energy [3]. WEPs play a vital role in providing energy, micronutrients, health benefits, etc., at little or no monetary cost, helping people through tough times such as harvest failure, and generating income for local farmers [2]. The growing interest in WEP resources nowadays stems from efforts to find alternatives to the industrialization and globalization of agriculture, to provide food security in times of agricultural crisis, to diversify human diets, to contribute to ecosystem service, to improve human health and to provide aesthetic, recreational and social values [1, 4,5,6].

Many ethnobotanical studies have been carried out worldwide to document and conserve traditional knowledge on WEPs. In Europe, ethnobotanical studies have been conducted in the north and the south. For example, 112 WEPs were recorded in Poland from 42 ethnographic and botanical source documents, but only half have remained in use since the 1960s [7]. In Spain, more than 400 species were recorded as WEPs, though many with primarily medicinal functions, and some were considered toxic [8]. In the Mediterranean, WEPs have been consumed as food for centuries, and their bioactive compounds are regarded to have great potential for developing into novel functional food products [9, 10]. WEPs contribute significantly to the nutrition of local populations in Africa [11, 12]. In North America, apart from nutritional value, WEPs have been deeply linked with ancestral culture [13, 14]. In South America, indigenous peoples have used WEPs since pre-Columbian times for food and other uses such as shelter, basketry, cloth, gums, unguents, and toxins [15]. In Chile, 330 native species were consumed as WEPs [16]. In Asia, ethnobotanical studies reveal that edible fruits are the most cited category [17] among the abundantly harvested WEPs by local people in Pakistan [18], Uzbekistan [19], India [20], Vietnam [21], and Japan [22].

In China, WEPs have been studied in different ethnic groups, e.g., Zang (Tibetan) [23], Hani [24], Yi [25], Mongolians [26], Dai and Yao [27], Dulong [28], Gelao [29], and Lahu [30], reflecting local bio-cultural diversity and rich TEK among various minority groups.

The Yao is an ethnic group mainly distributed in southern China [31]. Historically, the Yao people practiced slash-and-burn agriculture and hunting for a living. The Yao has become a trans-boundary ethnic group among China, Myanmar, Vietnam, Laos and Thailand [32]. They keep moving and searching for better living conditions. At present, Yao people are widely distributed in Asia, Europe, the United States, and Australia. There are around 3.2 million Yao people worldwide, among whom 2.6 million live in China [31]. For millennia, the Yao people have been famous for their wide distribution, rich culture, fortitude, and deep knowledge of nature [32].

Jianghua is the county with the largest Yao population among all Yao autonomous counties in China [31]. However, among the very few scientific studies about the Yao ethnic group, most were based in Yunnan and Guangxi [27, 33,34,35]. Most available reports mainly focus on the medicinal practice, while traditional dyeing technology has also gained increasing attention [36]. As the ‘Headquarter of the Yao’, studies on Jianghua have been very limited. Though wild edible plants are remarkably important among the wild plants used by the Yao in Jianghua, the available studies focused only on the medicinal plants sold on local herbal market on the Dragon Boat Festival [35, 37]. There is a huge gap between scientific study and TEK. The local environment and agricultural system are changing tremendously under economic and political development, e.g., a newly built dam, and tourism development.

We hypothesize that WEPs associated TEK and practice are being rapidly lost due to economic development and policy impacts. This study aims to record WEPs associated TEK and practice by the Yao people in Jianghua. This will provide a knowledge base to contribute to the regeneration of the local agricultural system and to biodiversity maintenance; to conservation and restoration of local cultural diversity; and to provide of ideas for new sources for local livelihood improvement.

Materials and methods

Study area

Jianghua County, known as the ‘Headquarter of the Yao’ in China, is the only Yao Autonomous County in Hunan Province and has the largest Yao population among the 13 Yao Autonomous Counties in China. It is located close to the borders of Guangdong, Guangxi and Hunan provinces in Southern China, between 110° 25′ S and 112° 10′ S and between 24° 38′ W and 25°15′ W (Fig. 1). The low latitude subtropical monsoon climate has plentiful rainfall and a mild temperature. With 2556 square kilometers of forests (79% coverage), Jianghua has a total stock of living trees of 15.3 million cubic meters, of which forest tree stock contributes 13 million cubic meters [31]. The rich forest provides rich resources and good habitat for biodiversity. Jianghua is diverse in biological resources, with 1,382 higher plant species from 668 genera and 181 families, representing 42% of the tree species in Hunan Province. Six species are first-level protected plants, and 26 species are second-level protected plants, according to the China Red Data Book. The Yao is the main ethnic group in Jianghua, accounting for 53% of the total population, with other minorities groups like Zhuang, and Miao also living there [31]. Based on long-term understanding and practice, the Yao people have formed a unique culture in harmony with nature, covering marriage and family, customs and habits, religious beliefs, and all other aspects in life [32]. In total, 30 sites from 12 townships of Jianghua Yao Autonomous County were selected for ethnobotanical survey (Fig. 1).

Fig. 1
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Location of study area of Jianghua Yao Autonomous County, Hunan Province, China

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Ethnobotanical data collection and statistical analysis

Literature review was conducted to obtain information about Jianghua County before the field survey, including its topography, climate, vegetation type and the Yao ethnic group [31, 32, 38]. Field surveys were conducted in October 2018, June 2019 and June 2023. A variety of methods had been used, such as key informant interview, semi-structured interview, participatory observation, and market survey [39, 40]. October is the main harvest season when there are many wild edible plants well-developed in autumn. In June, local people start to work more frequently in the mountains; the Yao believe the plants have accumulated enough energy and therefore are good to be consumed.

In total, 81 native Yao people (39 male, 42 female; 54 persons over 50 years old), were interviewed (Table 1). They were mostly local farmers, many of whom collected WEPs as a supplement for daily life. The primary content of interview consisted of “5W + H” questions [39, 40]:

  1. 1.

    What kind of WEPs do you collect? What’s its name in your language?

  2. 2.

    Which part of the WEPs do you collect?

  3. 3.

    Where and when do you collect WEPs? How often do you collect it?

  4. 4.

    How do you consume WEPs? What kind of process is needed?

  5. 5.

    What else do you use it for? Why do you collect WEPs for food?

Table 1 Demographics of informants
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The data collected in Jianghua was collated into an inventory containing all the WEP species and related information. Quantitative analysis was used to reveal the taxonomic characters, diversity of the modalities, usage parts and processing methods of wild edible plants (Table 2).

Table 2 Inventory of WEP species in Jianghua Yao Autonomous County
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Relative frequency of citation (RFC)

Considering informant consensus and to reduce researcher bias, the relative frequency of citation (RFC) of each WEP was calculated to objectively quantify the frequency of use of certain species and evaluate their relative importance based on the cited times [39, 41]. The determination formula of RFC follows:

$$\text{RFC}=\frac{FC}{N}$$

In the above formula, FC refers to the number of times one certain species of WEPs was mentioned by informants, N refers to the total number of informants interviewed in the survey. The value of RFC ranges from 0 to 1, the higher the RFC, the more important and valuable one species is within the studied area.

Voucher specimens were collected with assistance from the local people in local markets, villages, and nearby ecosystems. They were identified by a botanical expert, Professor Chunlin Long. All specimens were deposited in the Herbarium at Minzu University of China. The information compiled includes vernacular names, scientific names, taxonomic status, usage parts, life forms, processing methods and voucher numbers (Table 2). The families and genera of plants conformed to the APG IV system [42] and the nomenclature of plant scientific names followed World Flora Online (https://www.worldfloraonline.org) [43].

Results

Diversity of WEP species in Jianghua

Totally 130 WEP species, belonging to 89 genera and 49 families were documented (Table 2). The Poaceae family, with 13 different species, was the most widely collected; followed by Vitaceae and Rosaceae with seven species; then Ericaceae, Fabaceae, Actinidiaceae and Lamiaceae with six species each. Moraceae and Lardizabalaceae contribute juicy and delicious fruits. Only one species was reported for each of 22 families, accounting for 44.9%, and nine families (18.4%) provided only two species each. Many of the species are woody plants (40.8%), including trees (22.3%) and shrubs (18.5%). There were 47 species (36.2%) of herbaceous plants, and 30 (23.1%) lianas (Fig. 2).

Fig. 2
figure 2

Life habits of WEP species in Jianghua Yao Autonomous County

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The WEP species could be classified by edible parts (Fig. 3), including the whole plant, root, stem and leaf, flower, fruit, seed, and other parts like bulb, bark, petiole, rhizome, and tuber. The most commonly consumed part was fruit, with 51 species, followed by seed (18 species) and stem and leaf (15 species). For some plants, multiple parts can be consumed. For example, the rhizomes, stems, leaves and flowers of Houttuynia cordata are consumed. The fiddleheads of and starch extracted from rhizomes of Pteridium aquilinum var. latiusculum are cooked as vegetable or staple food. Crataegus hupehensis was consumed for its fruits and young stem and leaf. The various uses and preparation methods are recorded in Fig. 4.

Fig. 3
figure 3

Edible parts of WEP species in Jianghua Yao Autonomous County

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Fig. 4
figure 4

Way of uses of WEP species in Jianghua Yao Autonomous County

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For fruit use (Fig. 3), fresh consumption (Fig. 4) was the most frequent preparation method (44.6%). The Yao people collect fruit from their natural environment and eat them fresh while working in the mountains. In addition, fruits can be consumed in multiple different ways (Fig. 5). For instance, Choerospondias axillaris (Roxb.) B. L. Burtt & A. W. Hill fruits are used locally for alleviating hangovers; while the fruits of Diospyros kaki are helpful in runfei, moistening lung in order to reduce coughing, sore throat, stop bleeding, reduce blood pressure and Viburnum fordiae fruits are used as a farming calendar plant (Fig. 5), when the fruits turn red beside the field, it is time to harvest the crops.

Fig. 5
figure 5

Other uses of WEP species in Jianghua Yao Autonomous County

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Seeds are often gathered as a supplementary staple food (13.8%), some such as Castanopsis sclerophylla can be made into curd. Some, like acorns, must be thoroughly processed by leaching and cooking to remove bitter-tasting tannins before they are palatable [3]. The WEPs collected by the Yao people in Jianghua have multiple uses apart from food. Seventy-one species out of 130 (54.6%) were also used as medicine, 20 as tools, 11 as ornamentals and six as fodder. Trees from the family Fagaceae, which are common in Jianghua, provide seeds for starch and timber for construction and making furniture and tools (Fig. 5).

Analysis of the relative frequency of citation

The relative frequency of citation (RFC) indicates the local importance of each WEP [41]. The top 10 species are Ampelopsis grossedentata, Chimonobambusa quadrangularis, Crataegus hupehensis, Dioscorea alata, Patrinia villosa, Pleioblastus amarus, Pteridium aquilinum var. latiusculum, Pueraria lobata, Canna edulis, and Akebia trifoliata (Table 1). These plants are important either for their abundance, popularity, or wide availability. Called ‘Teng cha’ (vine tea), Ampelopsis grossedentata, the most frequently mentioned, is consumed as a daily tea substitute with health benefits. Dioscorea alata, Pueraria lobata, and Canna edulis, were important starch sources in past famines. The fiddleheads of Pteridium aquilinum var. latiusculum, common in southern China, are often consumed as a wild vegetable in spring [44]. Two bamboo species, Pleioblastus amarus and Chimonobambusa quadrangularis, produce bamboo shoots preferred by the Yao because of their delicious and smooth taste. Crataegus hupehensis, known as ‘Gungun cha’ (stick tea) by the Yao, is a favorite and common beverage species in Jianghua, served by every hostess to guests and visitors (Fig. 6).

Fig. 6
figure 6

Frequently collected WEP species in Jianghua Yao Autonomous County. a Actinidia melliana Hand.-Mazz, b Melastoma dodecandrum Lour., c Maclura cochinchinensis (Lour.) Corner, d Cornus kousa subsp. chinensis Q. Y. Xiang, e Holboellia latifolia Wall., f Rubus corchorifolius L.f., g Hibiscus mutabilis L., h Fagopyrum dibotrys (D. Don) Hara, i Patrinia villosa Juss

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Discussion

The Yao: a mountainous ethnic group Born to Eat Wild

The Yao people know and eat more WEPs compared with local people from other ethnic groups such as Zhuang and Han. For historical reasons, the Yao people live at higher altitudes in the mountains than other ethnic groups. The Yao people also have a reputation of ‘mountain people’, who live on mountains, depend on mountains, and eat on mountains [32]. Historically, the Yao people moved from one mountain to another from year to year, because of the depletion of natural resources [32]. From the long-term interaction with nature, the Yao people developed their own knowledge about natural environment and resources [31]. In contrast, the Zhuang and Han people live in the plateaus, running a rice-based agricultural system, with more cultivated vegetables and fruits, and less access to wild species [32].

On the contrary, in Jiangcheng, a boundary county between China, Laos and Vietnam in south-west China, the WEPs collected by Yao people share great similarity with other neighboring ethnic groups like Dai and Hani, which might because of their long-term interaction at the similar geographic environment [27]. While most of the WEPs were also herbaceous, the most used parts were tender stem and leaf as a potherb, rather than fruits. Fruit and rhizome were also among the topmost used parts. Another difference was that Yao people in Jiangcheng also use WEPs as sour condiment, which was not recorded in Jianghua [27]. This might result from the regional variance of environment, as Jiangcheng is located in the tropics while Jianghua is subtropical. People from the same ethnic group but have lived in different areas have developed different uses and knowledge of plants accordingly, which also contribute to the differentiation of different branch groups among the same ethnicity.

Many other studies on WEPs have been done using similar ethnobotanical methods in other areas in China. Though study areas were different, the results share similarities in many aspects such as that the majority of WEPs were herbaceous; most frequently consumed plant parts were fruits, young leaves, and stems; the most common way of consumption was eating freshly or cooking as vegetables; WEPs have multiple uses except food, like medicine, fodder, ornamental etc.; plant family with most species were among Rosaceae, Asteraceae, Fabaceae, Poaceae, Liliaceae etc. This phenomenon is consistent with the study of useful vascular plants in China [45]. Differences lie in the total number of species gathered as WEPS, fewer in Northern China and areas with higher altitude compared with Southern China in general, e.g. inner Mongolia [26], Qinling [46] and Tibet [23, 47] V.S. Yunnan [24, 27, 28, 30, 48, 49], Sichuan [25], Guangdong [50], Guangxi [51], Guizhou [29], Hunan [52]. This might be because of biogeographical reasons. In Southern China, the climate is much warmer and more humid, and plant species are more diverse. Relatedly, cultural diversity is also richer in Southern China, such as the number of ethnic groups within one province might be much higher in the south than in the north, a typical example is Yunnan, where there are more than 30 different ethnic groups. Specific ethnic groups also have unique patterns in the use of WEPs, such as in Tibet, WEPs were also used for religious ceremonies [47].

Baba: cultural identity food

One main target in collecting WEPs is for starch, mostly rhizomes and tubers, which have served as famine food and saved people through tough times. The Yao people collect Canna edulis, Pueraria lobata, wild yams (Dioscorea cirrhosa and Dioscorea polystachya), and ferns like Cibotium barometz and Pteridium aquilinum var. latiusculum (Table 2). After collecting, the starch from WEPs is mixed with sticky rice powder into diverse cakes, called baba in local language (Fig. 7), to support them through starvation. The elderly think baba from WEPs is much more delicious than those made from cultivated grains today, even though it demands more time and labor. The modern baba sold in local farmers’ markets are made from Oryza sativa, Zea mays and Sorghum bicolor in Jianghua (Fig. 7). Culturally, the Yao people consume baba on a daily basis. The first author participated in the process of making baba from pumpkin (Cucurbita moschata), taro (Colocasia esculenta) and rice (Oryza sativa) in an interviewer’s house in October, 2018 (Fig. 7). Additionally, the Yao people will also make aibaba by adding tender leaves of Artemisia argyi to control intestinal parasites. Zongzi, a wrapped baba, is viewed as a cultural food for Chinese symbolism [53]. As a special form of baba, zongzi is also very common and popular in Jianghua (Fig. 7), especially during the Dragon Boat Festival. Baba can be regarded as a cultural identity food for the Yao [54].

Fig. 7
figure 7

Baba—a cultural identity food. a Gaoliang baba (Sorghum bicolor (L.) Moench). b Undyed (in white) and dyed baba (in yellow, dyed by Gardenia jasminoides Ellis). c Fried pumpkin baba (Cucurbita moschata Duchesne). d Two major forms of zongzi (Wrapped baba) named by their shapes (triangle zongzi and pillow zongzi). e Triangle zongzi sold on local market. f Traditional way of cooking pillow-like zongzi

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WEPs: benefits versus risks

WEPs are of vital importance to indigenous communities in providing nutrients, increasing dietary diversity, promoting social interaction, reducing economic pressure, and enhancing cultural identity. Yao people in Jianghua gather WEPs because: (1) WEPs are more delicious and flavorsome than cultivated market plants; (2) WEPs are healthier, without artificial fertilizers and pesticide; (3) WEPs are diverse, supermarket selections are too limited to satisfy needs for diverse materials and different recipes; (4) some WEPs have desired medicinal functions; (5) WEP collection is more interesting, e.g., the possibility to find rare but valuable plants; 6) WEP collection is a good way to socialize, e.g., meet other collectors, and to share and cook collected WEPs with families and friends. Some city residents forage WEPs when returning to the countryside home, as a way of recreating childhood experiences. There is a new trend among local Yao people of sharing their unique daily life on social media such as Tik Tok. Similarly, studies in Europe also showed that people harvest WEPs not only to satisfy physical needs but also for cultural needs such as recreation and social purposes [1, 4].

Despite the benefits of WEPs there are doubts and concerns about safety, particularly concerning toxicity. Studies have reported the risks of consuming toxic plants [5, 7]. Illness from consuming wild harvested plants can result from failure in plant identification by confusing similar edible and non-edible plants, or lack of knowledge in processing. Bitterness in plants generally indicates toxicity [7], while the Yao people view bitterness as medicinal and therefore consume many bitter plants. Of the 130 WEPs recorded, five are known to be bitter, reflected in the nomenclature, such as bitter sow-thistle (Ixeris polycephala), bitter bamboo shoot (Pleioblastus amarus), bitter chestnut (Castanopsis sclerophylla), bitter tea (a variety of Camellia sinensis) and man’s bitter vegetables (Patrinia villosa). By eating bitter food, Yao people memorialize their tough history, reminding them that life is not easy, and hard work is necessary for survival. It is believed in Yao medicine that bitterness is good for the liver, and detoxifying, clearing extra heat and reducing blood pressure [32]. Therefore, the reasons and risks/benefits of eating bitter WEPs and other risks such as toxicity merit further investigation.

WEPs as folk medicines

According to Chinese folk wisdom, for enhancing body function, medicine is good, but food is better. In our study, 54.5% WEPs were also used as medicine (Table 2), and Yao folk doctors commonly prescribe these plants. In China, some recipes use specific combinations of food and medicine, cooked together to enhance healthy function. Research on Hakka revealed 42 medicinal herbs were used in soup in Fujian for health benefits [55]. Another common medical use of wild plants by the Yao was taking herbal baths. Similarly, former studies also showed Yao people in Guangxi and Yunnan made use of various wild plants in medical herbal bath, especially after giving birth [34]. Previous studies showed that one popular way to consume WEPs was as recreational beverages such as tea, tea substitute and alcohol [5, 27, 37]. WEPs were either brewed into or infused in alcohol by Yao people. In Jianghua, the three most welcome “tea” (or “cha” in Chinese) varieties are Tengcha, Kucha, and Gunguncha, consumed frequently for their potential medicinal functions and served to visitors. Compared to normal tea (Camellia chinensis), tengcha (vine tea) is a tea substitute made from a wild climbing plant, Ampelopsis grossedentata. The special white powder on surface after fermenting is thought to be beneficial to health by Yao people. The major antioxidant compound in vine tea is dihydromyricetin [56]. Studies suggested tengcha has multiple physiological functions such as anti-inflammatory [57], anti-bacterial [58], anti-tumor and anticancer effects [59]. Unlike Camellia sinensis, and despite the multiple functions and potential uses of tengcha, it is not yet cultivated. If local government can develop planting tengcha at scale, combined with cultural tourism, it will be helpful to provide job opportunities, increase incomes, and enhance cultural confidence.

Plant blindness and conservation

As the younger generation moves to urban areas for better jobs, education and more convenient life, they lose touch with traditional lifestyle, and become more ‘plant blind’, ignoring or overlooking plants in society and daily life [60]. Some lose interest in old-fashioned traditions, others doubt the safety, hygiene, or nutritional value of WEPs. Compared with collecting WEPs, buying food from markets is much more timesaving and convenient. However, mankind relies on a narrow range of foods, which is problematic in feeding the growing population and providing all necessary nutrients [61]. WEPs can have high nutritional values, providing diverse sources of fiber, vitamins, proteins, carbohydrates, fatty acids, and bioactive compounds [62, 63]. WEPs provide ingredients to diversify people’s diets [64], and improve diversity and resistance of food ecosystems under climate change [5, 6]. A Norwegian study indicated that the ethical motivation driving vegetarianism is environmental and animal rights [65], and WEPs are an ideal option to reduce consumption of animal products.

Ecologically, there is a risk of over-harvesting especially for species with high socio-economic value. Harvesting amounts are not effectively controlled, which may threaten slow-growing species, such as those foraged for underground parts, e.g., Cibotium barometz, Dioscorea alata, Smilax glabra, and etc. Digging for collection of such parts causes much disturbance to the microenvironment and may greatly impact the habitat and local ecosystem. Nevertheless, there is a Yao folk consensus concerning protection of wild gathered plants such as ‘collecting bigger plants and leaving smaller plants’ and ‘harvesting older plants while leaving the root system’. Similar folk wisdom occurs in Norway, which was assessed as having sustainable foraging [1]. Study among the Yao people in Vietnam also indicated TEK would enhance resiliency to climate change if better integrated and applied into adoption of new plans and policies [66].

With the building of the Centian River Dam, the local environment has been going through huge changes in recent years. The river had historically bred rich diversity. However, the new dam has lifted the waterline by more than 50 m, submerging ecosystems that used to be a great source of wild food. Meanwhile, the local government has tried hard to develop touristic villages for poverty alleviation, which destroyed some agricultural systems and landscapes. Local villagers changed from farmers and foragers into businessmen or performers, abandoning much of their traditional way of life. Similarly, an ethnobotanical study on traditional medicinal plants used by the Mien (Yao people) in Thailand found the erosion of traditional knowledge and practice among young generations due to transition of lifestyle and also moving away from mountains [67]. Studies show that land use change, urbanization, overexploitation and climate change are major threats to the conservation of WEPs and related TEK [6, 68]; these are also affecting the Yao people in Jianghua.

Conclusion

This research is an ethnobotanical study on wild edible plants in Jianghua Yao Autonomous County, Hunan, China. One hundred and thirty species (belonging to 89 genera and 49 families) of WEPs and the information on their habits, edible parts, and preparation methods were documented. Based on our analysis, the most widely consumed parts of WEP species include fruits, seeds, and tenders. The most common processing methods for WEP species were eating fresh and cooking as a potherb. While more than half WEPs were also used as medicine, one common way was using as tea substitute. Baba can be defined as a cultural identity food, and the most important species for it are Ampelopsis grossedentata, Chimonobambusa quadrangularis, Crataegus hupehensis, Dioscorea alata, Patrinia villosa, Pleioblastus amarus, Pteridium aquilinum var. latiusculum, Pueraria lobata, Canna edulis, and Akebia trifoliata. These results were closely related to the local biodiversity and the Yao people’s TEK and practice. The threats of WEPs over-collection, TEK inheritance loss and challenges for local agroecosystem have been analyzed. The WEPs collection and consumption practice, along with the local agroecosystem are facing severe problems related to natural resource conservation, environmental protection, economic development, and water reservoir construction. Suggestions related to the protection of TEK and agroecosystem include increasing studies, educating younger generations and collaborations among experts, local communities and stakeholders. In conclusion, there are abundant WEPs resources in Jianghua, and the Yao ethnic group has developed WEPs related TEK and practice in their sustainable agroecosystem. However, this region and culture is suffering a series of threats in the contemporary age. It is therefore critical and urgent to ensure its sustainability for local inhabitants and our future.