Introduction

Throughout the long history of survival and development, mankind has developed a close relationship with plants [1]. Approximately 13% genera of vascular plants are available as dietary food, followed by ornamental plants (26%) and medicines (16%) [2]. As the archetype of biocultural diversity, food plants establish a connection between the environment and biodiversity, while also bridging human society with cultural richness [3]. Numerous edible flowers are integral to the gastronomic heritage of various countries and play a crucial role in human nutrition and food security [4,5,6,7].

Edible flowers (EFs) are broadly defined as plants in which entire flower organs or their components are deemed edible. These flowers serve various purposes, such as in medicine, flavor extraction, and as essential ingredients within the food and medicinal sectors [8, 9]. It is reported that there are 180 species of common EFs, belonging to 97 families and 100 genera, globally consumed in all kinds of food and drinks [10]. Research and review articles on its nutritional and phytochemical elements have always increased [11]. Studies show that many EFs are rich of protein, vitamins, minerals, fiber and carbohydrates. A total of 302 bioactive compounds including flavonoids, terpenoids, phenylpropanoids, alkaloids and organic acids, with 22 biological activities were summarized [12,13,14]. Nowadays, EFs have transformed into valuable sources of both sustenance and medicinal benefits, capable of enhancing people’s well-being. Regrettably, their traditional importance frequently goes unnoticed or is overlooked [13,14,15]. Some ethnobotanical studies on EFs have demonstrated that their cultural attributes hold the potential to contribute to local economies, the preservation of biodiversity, and the advancement of rural development [16,17,18,19]. Nonetheless, the quantity of such studies is notably lower in comparison with the extent of their phytochemical research.

Flowers have been utilized by Chinese people for a long time in various ways, including their consumption as a source of sustenance. Some 2500 years ago, the Chinese poet Qu Yuan wrote about eating flowers in his poem ‘Li Sao’: “朝饮木兰之坠露兮, 夕餐秋菊之落英”, which means taking dew drops falling from magnolia flowers as a drink in the morning, and taking petals falling from chrysanthemums as a meal in the evening. This is the earliest record of Chinese flower-eating culture [20].

In Yunnan Province, which is rich in both biodiversity and cultural diversity, there are more than 300 EF species consumed by different linguistic people there. Those species belonged to 74 families and 178 genera [21]. Depending on their habits, living environment and altitude, the species of flowers chosen for consumption vary greatly from one group to another. The diversity of edible parts of flowers consumed, and the processing and cooking methods reflected rich EFs’ traditional knowledge [21, 22].

Xishuangbanna is home to a wide variety of edible plants, many of which have been consumed for centuries by local communities for food and medicinal purposes [23, 24]. It is also an important ethnobotany’s birthplace in China. The first ethnobotanical paper in China published in 1982 focused on useful plants in Xishuangbanna, where 7 EFs were recorded. These included Bauhinia variegata L., Sesbania grandiflora (L.) Pers., Buddleja officinalis Maxim., Gmelina arborea Roxb., Elsholtzia rugulosa Hemsl., Smilax zeylanica L. and Musa spp. [25]. Previous ethnobotanical investigations revealed that the floral components of food plants are prominently utilized as edibles in the region, with a minimum of 23 EFs being commonly employed by the local population [24, 26]. The culture of EFs is a crucial part of traditional knowledge and practices of different linguistic groups in Xishuangbanna such as the Dai, Hani, Jinuo, Yao, Lahu, Lisu, Yi, and Han communities residing in that area [27]. The long history of flower-eating and the rich variety of EF is the result of local people’s adaptation to their ecological environment [28].

In conjunction with the previously mentioned list of the EFs, an extensive ethnobotanical literature search encompassing edible plants in Yunnan and beneficial flora in Xishuangbanna was conducted through reputable online scientific databases including Google Scholar, Sci Finder, Web of Science, Springer Link, PubMed, Wiley, as well as Chinese databases like CNKI, Baidu Academic, and Chinese Science and Technology Periodical databases. The keywords such as “edible flowers,” “eating flowers,” “traditional use of flowers,” “flowers culture,” “edible plants,” and “food plants” were used. The publications were filtered for the Chinese, English and Japanese. Based on the literature review, we found that there are many edible flower species distributed in Xishuangbanna. The local people have the tradition to collect and consume EFs. Unfortunately, it lacks documentation of flower food and associated traditional knowledge, or systematic ethnobotanical investigation.

Eating flowers was once a common practice in human society. However, with the development of society, especially the popularity of fast food among the young generation, the flower-eating culture has gradually disappeared in many countries [29]. The flower-eating culture prevalent among Yunnan societies reflects the local people’s deep understanding of plants and nature, containing folk ecological wisdom and key clues to the sustainable development of local communities [30]. In recent decades, rapid economic development happened in China. In particular, massive tourism and commercial plantations of rubber and tropical fruits have emerged in Xishuangbanna. These economic activities have resulted in the rapid decline of the flower-eating culture. It is necessary and urgent to preserve traditional knowledge associated with EFs in Xishuangbanna. The edible flower in this article refers to the floral parts utilized by people for food, drink, or food supplementary material purposes. It may be flower only, or flower with other parts of the plant when consumed. The main purposes of this study were to (1) document the EFs consumed by different linguistic groups in Xishuangbanna, (2) reveal the flower-eating culture there, and (3) propose strategies for its conservation and future development.

Methods

Study area

Xishuangbanna Dai Autonomous Prefecture is the study area of the present paper. It is located in the southernmost part of Yunnan Province, China. The Lancang-Mekong River flows through this prefecture from the north to the south, and the whole territory belongs to its watershed. The total land area of the prefecture is more than 19,000 km2, bordering Laos and Myanmar to the south (Fig. 1). It has tropical monsoon climate with an average annual temperature of 15.1–21.7 °C. The annual precipitation varies from 1000 to 2500 mm [31]. Throughout the year, the region maintains a warm and humid climate, characterized by the absence of harsh cold during winter, the absence of extreme heat in summer, and favorable light conditions. Xishuangbanna is the home to the largest tropical forest in China, with an area of approximately 15,500 km2 (81% forest coverage) [28]. The geographical environment and rainforest climatic conditions have nurtured rich local plant resources, with nearly 5000 species of higher plants, accounting for about 16% of China’s higher plant species, making it one of the areas with the richest biodiversity in China [32].

Fig. 1
figure 1

The study area. The colored map is Xishuangbanna Prefecture, in which markets in towns/townships and villages investigated are marked with black dots and blue/pink triangles

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Xishuangbanna Prefecture, under the jurisdiction of Jinghong City, Mengla County and Menghai County, has been a multi-ethnic settlement since ancient times. In addition to the Dai people, there are 12 other linguistic groups, including the Han, Hani, Lahu, Bulang, Yi, Jinuo, Yao, Wa and Hui. The ethnic minority population is about 790,000, or 69.97% of the total population, of which the Dai are the most numerous, accounting for about one-third of the total population [33]. In the ancient Dai language, “Xishuangbanna” means “ideal and magical land of happiness” [28]. Each ethnic group has its own language and traditional culture as well as its way of perceiving and using local natural resources, creating a rich cultural diversity in Xishuangbanna [24].

The Dai people live in the basins and lowlands of Xishuangbanna, with a population of 334,500. They have their own oral and writing language belonging to the Zhuang-Dai branch, the Zhuang-Dong language group, Sino-Tibetan family. The Dai people believe the Hinayana Buddhism and animism. They grow sticky rice in the paddy fields and manage homegardens. The glutinous rice is their staple food. Vegetables are mostly grown in homegardens, while wild food plants are collected as supplements (www.xsbn.gov.cn, accessed 21 August 2023).

The Hani people live in the mountains of Xishuangbanna. They have other names such as Aini and Akha, with a population of 211,800. The Hani do not have written language. Their spoken language belongs to the Yi branch, Tibetan-Myanmar language group, Sino-Tibetan family. They grow rice, upland crops such as maize and tea. It is common for the Hani people to collect wild food plants. They believe animism and worship ancestors (www.xsbn.gov.cn, accessed 21 August 2023).

There are 62,100 Lahu people living in Xishuangbanna. They speak Lahu language, which belongs to the Yi branch, Tibetan-Myanmar language group, Sino-Tibetan language family. Most Lahu people believe animism, but some of them believe Buddhism. They live in the mountains and practice upland farming. Collecting edible plants become one of their essential activities.

The Yi people live in the Northeastern part of Xishuangbanna, with a population of 59,500 (www.xsbn.gov.cn, accessed 21 August 2023). They have oral and written language, belonging to the Yi branch, Tibetan-Myanmar language group, Sino-Tibetan family. The Yi people believe animism and worship ancestors. They grow upland crops and collect edible plants in the mountains.

There are 52,800 Bulang people living in Xishuangbanna (www.xsbn.gov.cn, accessed 21 August 2023). They speak their own language but do not have written characters. Their language belongs to the Bulang branch, Mon Khmer group, South Asian language family. They live in the uplands of Menghai County, believe the Hinayana Buddhism. It is essential for the Bulang people to manage teagardens and collect wild edible plants to support their lives.

Most Jinuo people concentrate to live in Jinuo Township of Jinghong City, with a population of 25,800 (www.xsbn.gov.cn, accessed 21 August 2023). They grow upland crops while collecting becomes important livelihood form. The Jinuo people believe animism, and worship their ancestors.

The Yao people live in the mountainous areas of eastern Xishuangbanna, with a population of 23,700 (www.xsbn.gov.cn, accessed 21 August 2023). They do not have written language. Their spoken language belongs to Yao branch, Miao-Yao group, Sino-Tibetan language family. The Yao people grow upland crops and collect wild edible plants for food.

In addition to the Han Chinese, a few thousands of Miao, Wa, Zhuang, Jingpo and Hui people also live in Xishuangbanna. The Hui ran good business, while the others earn their livelihoods based on agricultural production. Most Han people in the prefecture migrated from Hunan Province in 1960s to clear lands for rubber plantations.

Traditionally, the Hani, Bulang, Wa, Yao, Miao, Yi, Lahu and Jinuo people who lived in the mountainous areas practiced shifting cultivation (slash-and-burn agriculture). They cultivated upland rice, taro (Colocasia esculenta), buckwheat and beans, but rarely grew vegetables. The ancestors of uplanders and Han Chinese in Xishuangbanna had planted tea seedlings in natural forests. The old tea gardens scattered in the prefecture can still produce high-quality tea products called Pu-er tea.

Nowadays, all people in Xishuangbanna have gotten rid of poverty and lived at a higher-level livelihoods. The locals who live in lowlands earn incomes from rubber and tropical fruit productions, while those in uplands from tea production. Also, the tourism in Xishuangbanna brings a lot of opportunities to the local people. In general, their economic status is at the middle level in the country. However, the locals still collect a lot of wild edible plants from the forests, farming lands, roadsides and wetlands for daily lives. It becomes a custom or traditional culture to gather food plants from the wild lands.

Field survey and data collection

The field ethnobotanical surveys were conducted in Xishuangbanna during five visits in 2021 and May 2023. It covered 48 villages and 19 markets (Fig. 1) in all three county-level areas, Menghai and Mengla, and Jinghong in the prefecture. Different linguistic groups including Dai, Hani, Bulang, Jinuo, Yao, Miao, Lahu, Yi, Wa, Lisu and Han Chinese were involved.

The maps were downloaded from the official site (http://bzdt.ch.mnr.gov.cn/). The investigation sites including markets and villages were marked based on ArcGIS 10.7.

In villages, free listing, key informant interviews and participatory observation were conducted [34, 35]. In total, 201 people ranging from 16 to 87 years old were interviewed during the field surveys, including 92 females. The informants were mostly interviewed in local markets, reaching 128 people consisting of 65 females and 63 males (Table 1). Among these respondents, 24 people were selected as the key informants. In the context of this article, EFs are defined as floral components consumed by individuals for culinary, beverage, or supplementary dietary purposes. Consumption may involve the flower alone or in combination with other plant parts. The interviews were conducted using a semi-structured approach, covering topics such as EF species, their pronunciation, edible parts, processing techniques, medicinal advantages of consuming the flowers, additional uses of the consumed plant, and the motivations behind their consumption.

Table 1 Demographic characteristics of the interview respondents
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The linguistic group, age, education level and occupation of informants were also recorded. Before the interviews, each informant who participated in was informed of the purpose of the project, and their consent was obtained.

The availability of the EFs influenced by seasons and processing, making comprehensive coverage challenging in limited field surveys [19]. A pivotal reference for this study was the comprehensive investigation by Prof. Yitao Liu and Prof. Chunlin Long (one of the corresponding authors of this paper), pioneers in the field of edible flowers in Yunnan [21, 22]. Local market was the entrance of local food system with the largest concentration of flower-eating plants in the region [3]. They were also gathering places for traditional knowledge from the stallholders and consumers [17]. In our survey, we examined 19 markets within an urban area and 11 towns across Xishuangbanna. Our interviews encompassed EFs' vendors as well as select consumers purchasing these items. The traded flower-eating plants in the markets and supplementary insights shared by local individuals (both vendors and consumers) were meticulously documented.

The flowers collected and consumed by the local people in Xishuangbanna can be divided into different categories according to their edibility of different parts of the flower. A single flower consists of bract, pedicel, receptacle, calyx, petal and corolla, stamens (filament, anther and pollen), pistils (ovary, style and stigma), nectars, and sometimes appendix. In many cases, there are inflorescence consisting of flowers. People consume flowers together with leaves and stems if all these parts are edible or taste better. But sometimes only a single part of flower (for example, petal or pedicel), or male flower only, is selected for food. Therefore, the edible parts of EFs were recorded and calculated in the market surveys and field investigations.

The multiple uses of flowers including their cultural values were also investigated. Some species of EFs consumed as food can be used for different purposes such as ornamentals, medicine and pigment. The EFs have contributed to the development of local culture in Xishuangbanna. Their values with cultural significance were also investigated and recorded, in addition to their role as food.

The voucher specimens were collected through the process of conducting market surveys or en route to subsequent locations. The nomenclature of all vascular plants follows Plants of the World Online (Kew) (powo.science.kew.org, accessed on 16–17 August 2023) and World Flora Online (www.worldfloraonline.org, accessed on 23–28 May 2023). Prof. Chunlin Long and Zhuo Cheng identified the plant species, and the voucher specimens were deposited in the herbarium at Minzu University of China, Beijing.

Quantitative analysis

Quantitative analysis of the data was conducted to understand the diversity of edible flower species in Xishuangbanna. It will help to evaluate the potential of traditional knowledge of the target communities. Thus, the number of species, the number of respondents who provide information, and information on the edible flower species were presented based on the citations. Our quantitative analysis was followed by ethnobotanical indexes using relative frequency of citation.

The relative frequency of citation (RFC) in this study was used to evaluate the local importance of EFs in Xishuangbanna. The formula for RFC is RFC = FC/N, which means the number of respondents mentioning an EF divided by the total number of respondents [36]. FC is the number of respondents who gave citations at each species, and N is the number of respondents. The index varies from 0 to 1. A higher RFC value means more local people know the EF [37]. The RFC values for each EF are added to the database.

Results

Species diversity of EFs in Xishuangbanna

Based on our field surveys and literature review, 212 taxa (including species and varieties) belonging to 58 families and 141 genera are documented as being used as EFs in Xishuangbanna. Their vernacular names, Chinese names, distributions in Yunnan, habitats, used parts, use types, methods of preparation for food, additional uses, RFC values and voucher numbers are also listed in Table 2.

Table 2 Inventory of edible flowers consumed by different linguistic groups in Xishuangbanna, Yunnan, China
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Of all the recorded EF species, Zingiberaceae was the largest family with 17 species (8.0%), followed by Leguminosae and Rosaceae each with 16 taxa (7.5%). Brassica was the largest genera with 8 taxa (3.8%). Most EFs were cultivated or can be cultivated (127 species), more than wild (83), imported (8) and escaped (5) ones.

There were 121 taxa (57.1%) distributed in the south of Yunnan or tropical Yunnan, such as Limnocharis flava, Trevesia palmata, Pseuderanthemum polyanthum and Ficus auriculata (Fig. 2a–d). A total of 80 EFs (37.7%) can be found in the Yunnan or most areas of Yunnan, showing the wide flower-eating custom or culture in Yunnan province. For example, the flowers of Cucurbita moschata (both male and female flowers, mostly male flowers consumed only), Brassica rapa var. glabra and Colocasia esculenta are very common and widespread as vegetables (Fig. 2e, g, h). The inflorescence of Allium tuberosum (Fig. 2f) and Nepeta cataria (Fig. 2i) are always used as seasonings in various stir-fries and grilled fish throughout Yunnan.

Fig. 2
figure 2

EFs used as vegetables and seasonings. a Limnocharis flava (L.) Buch.; b Trevesia palmata (Roxb.) Vis.; c Pseuderanthemum polyanthum (C.B.Clarke) Merr.; d Ficus auriculata Lour. (hypanthium); e Cucurbita moschata (Duch. ex Lam.) Duch. ex Poiret (female flowers); f Allium tuberosum Rottler ex Sprengle; g Brassica rapa var. glabra Regel (with leaves and stems); h Colocasia esculenta (L.) Schott. i Nepeta cataria L. (with leaves and stems)

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Cultural diversity of edible flowers

The edible parts of the EFs used for food in Xishuangbanna were various. These include all parts of the flower, inflorescence, flower (entire flower as a whole), petals, flower buds, nectar, peduncle, calyx, pollen, receptacle, stamens, spathes and scape (Fig. 3). Consuming an entire flower as a whole and consuming specific parts of the flower are distinct concepts. When referring to eating all parts of the flower, it implies that the different components of the flower organ can be consumed individually. When consuming flowers of Bombax ceiba, for example, its fresh stamens are stir-fried as dishes and its petals are cooked to make soups, while the dry flowers are used in herbal tea. The “flower” means that the whole flower is eaten together without separating the different parts of the flower organ. Through our investigation and statistics, the most consumed part was inflorescence as a whole (85 species, 40.1%), followed by all parts of flower (60, 28.3%). A total of 181 EFs (85.4%) exhibit the presence of multiple edible parts. This finding highlights the profound knowledge and extensive utilization of local plant resources by the indigenous population.

Fig. 3
figure 3

The diversity of flower parts used for food. The number refers to the species number, and the percentage refers to the ratio of each category of edible part of flowers

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Mostly, flowers for eating were collected or used alone (156 species, 73.6%). They were also used with other parts of the plant, being collected or consumed with leaves, stems, rhizomes, fruits, shoots and pods (Fig. 4). Leaves were the most often consumed together with flowers (43 species, 20.3%). Flowers from Brassica plants (Brassica juncea, B. oleracea, B. rapa var. chinensis, B. rapa var. glabra, and B. rapa var. oleifera), Ocimum basilicum, Nepeta cataria, and Solanum americanum were always gathered and consumed together with their stems and leaves. They were common in the Xishuangbanna markets and are well-known by locals with higher RFC values. Interestingly, when we conducted the semi-structured interviews in the villages, respondents would never mention them unless we initially asked if they were EFs first. In locals’ perceptions, these EFs are a little different from other leafy vegetables because they were always commonly cultivated and had small flowers and limited cultural significance.

Fig. 4
figure 4

The diversity of other edible parts when collecting/ consuming flowers. The percentage refers to the ratio in all edible flower species

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All EFs species were also classified by their use types. In Xishuangbanna, locals used EFs as a vegetable, tea-scented flower, tea substitute, seasoning, snack, food dye, beverage, and side dish (Fig. 5). Vegetables were the most common product type with 184 EFs (86.8%). It was also common to use EFs as seasonings, tea substitutes and snacks. The majority of EFs (25.9%) have more than one use type.

Fig. 5
figure 5

The diversity of use type of EFs. The number refers to species number, and the percentage refers to the ratio in all edible flower species

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Due to different EFs and dietary cultures, food made from EFs was prepared using a variety of methods, including stir-frying, cooking in water, steaming, stewing, pickling, frying, roasting, baking, brewing, cooking with something, dying something, scenting tea, collecting nectars as snack, making congee, soup or cakes and as salad, seasonings or tea substitute (Fig. 6). Stir-frying (138, 65.1%) was the most common way to prepare these flowers, followed by cooking in water (108, 50.9%). The term “other” includes brewing, soaking in liquor, cooking as a vegetable in a hot-pot, and making sweets.

Fig. 6
figure 6

The diversity of methods to prepare EF food (SF: stir-fried; CW: cooked in water; ASA: as a salad; AT: as tea substitute; ST: stewed; FR: fried; MCS: making congee or soup; RO: roasted; STE: steamed; PI: pickled; ASE: as seasonings; CWS: cooked with something; SCT: scenting tea; MC: making cakes; BA: baked; CN: collecting nectars as snack or sweetener; DS: dying something)

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Furthermore, 29 species of edible flowers (EFs) (13.7%) necessitated boiling, blanching in hot water, or the removal of certain parts such as peels and stamens prior to cooking and consumption. Among these, Mayodendron igneum is a notable EF long utilized in Xishuangbanna and engaged in games by the Jinuo community (Fig. 8b). Children from the Jinuo group delight in blowing into its tubular corolla, reminiscent of an orange trumpet. To prepare the flowers for food, the calyx and stamens were removed and then, blanched in water to eliminate bitterness. They can then be stir-fried, boiled, or used as a salad. Some slightly toxic EFs, such as Rhododendron flowers, also required pre-treatment to reduce their toxicity. Colocasia esculenta is a very common EF in Yunnan. Before consumption, people remove the peel of the petiole and spadix from C. esculenta. Even so, some people may experience mild discomfort, such as numbness of the tongue or a sore throat. However, rest assured that it is safe for consumption in this manner.

Multiple uses of flower-eating plants

All EFs have multiple uses beyond food. A total of 179 EF species (84.4%) showed medicinal values (Fig. 7). Apart from flowers, other parts of some species, such as roots, stems, leaves, fruits and seeds, can be used for a variety of purposes. These include clearing heat, invigorating the stomach and promoting blood circulation.

Fig. 7
figure 7

Additional uses of flower-eating plants. The number refers to species number, and the percentage refers to the ratio in all edible flower species

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Flower-eating plants were also used as ornamentals, fodder, and timber (Fig. 7). The pseudostem of Musella lasiocarpa was edible, and it was an important feed for local pigs. Musa acuminata leaves were commonly used for containing food and as tableware in various ways. Kernel of Prunus armeniaca can be used for skincare. The bark fibers of Thespesia lampas were utilized for producing ropes and the seed hairs of Bombax ceiba for beddings. The chopping boards made from the trunk of Senna siamea were sold in many markets. EF resources affect every aspect of people’s lives in Xishuangbanna.

EFs with significance in a traditional culture based on RFC values

The RFC values of each EFs were calculated to reflect their local importance. Bauhinia variegata var. candida, Brassica oleracea var. botrytis and Musa acuminata have the highest RFC values. While Brassica oleracea var. botrytis is renowned worldwide and widely used in China, it holds no special meanings in Xishuangbanna. Musa acuminata is a common and distinctive vegetable frequently consumed by the locals (Fig. 8c). The plant’s inflorescence, in particular its bracts and petals, can be utilized as a culinary ingredient in various dishes. It can be prepared by stewing or stir-frying with pork, roasting, steaming or boiling in water. The Yao people in Yiwu Town, Mengla County, have a tradition to celebrate a Chinese festival called Long-tai-tou, the Dragon-Raising-Head Festival. During the festival, the whole community eats wild banana flowers (inflorescence of Musa acuminata) so that they would have a good harvest year-around. Traditionally, the flower is stir-fried with pork and then, wrapped in glutinous rice, making it a delectable festival delicacy.

Fig. 8
figure 8

Some EFs with significance cultural values in Xishuangbanna (a Bauhinia variegata var. candida (Roxb.) Voigt; b Mayodendron igneum (Kurz.) Kurz.; c Musa acuminata Colla; d Buddleja officinalis Maxim.; e1 & e2: Gmelina arborea Roxb.)

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Bauhinia variegata var. candida is a common species in the south of Yunnan. The flowers (Fig. 8a), young leaves and pods were consumed as vegetables in Xishuangbanna. After blanching in hot water, the flowers can be stir-fried, cooked in water, fried, salad or stewed. The ethnic groups, particularly the Jinuo people in Xishuangbanna, have a long history of using the flower of Bauhinia variegata var. candida, which commonly known as “jiebo.” Living in the mountains and traditionally practicing slash-and-burn agriculture, the Jinuo people consume its flowers along with this young leaves. Its tender fruits (pods) can be preserved and eaten for up to two months. The jiebo flower serves as an indicator species for farming and holds cultural importance for the Jinuo farming. The Jinuo’s old saying “When the jiebo blooms and the cicada chirps, it is time to sow seeds” indicates the significance of Bauhinia flower in agricultural activities. The jiebo flower holds a social significance among the youths, symbolizing a period of heightened social interactions when in full bloom. Climbing higher up the tree to gather more jiebo flowers is seen as a demonstration of capability and becomes an attractive trait to young girls.

Buddleja officinalis and Gmelina arborea flowers possess the third-highest RFC values, signifying their important roles in flower-eating culture in Xishuangbanna (Fig. 8d, e1). B. officinalis was frequently employed as a food dye. Its inflorescences are sun-dried, and during rice preparation, they were immersed in hot water until the water takes on a yellow hue. Following this, glutinous rice was soaked in the water containing the Buddleja pigment for 4–5 h. Subsequently, the water was filtered, and the rice was steamed using a wooden pot. The golden yellow rice is then made with a subtle fragrance, which is a traditional festival food on March 3rd of the Chinese Lunar Calendar. The inflorescence in boiled water can also be utilized as tea substitute. The cake made from G. arborea flower was very common and can be easily found in markets (Fig. 8e2).

Discussion

Flower-eating culture as a biocultural contribution to biodiversity conservation

The practice of consuming flowers is not confined to a particular region or linguistic group; rather, it’s a widespread human custom [10]. Nevertheless, the species consumed, the motivations, and the distinct behaviors related to flower consumption can vary across cultures [19]. Among the most common 15 species worldwide counted by Lu et al., there are only 8 species included in Table 2, implying the difference between EF species in Xishuangbanna and other places in the world [10]. The significant difference is due to abundant local biodiversity and deeply rooted traditional culture in Xishuangbanna, which represents rich biocultural diversity [40].

Cultural heritage and biological diversity share an intricate bond, with the associated knowledge being equally crucial alongside the diverse array of the EFs [41]. Thorough documentation of the local traditional knowledge holds a vital role in safeguarding biocultural diversity [42]. Within Xishuangbanna, the traditional knowledge regarding the usage of the EFs stands as a central and representative component of the flower-eating culture. This knowledge encompasses an elaborate range of practices. That means 13 categories of flower parts can be prepared in 21 distinct methods, yielding 8 distinct types of food. The local community possesses a clear understanding of which EFs require specific processing before cooking to eliminate toxicity or bitterness. They also understand which ones can be harmoniously cooked with other plant parts such as stems and leaves.

Edible plants are part of the biocultural resources that ethnic groups possess [43]. EFs with cultural identities are also part of the local culture or plant culture [44]. The phenomenon of consuming flowers serves the purpose of fulfilling individuals’ physiological requirements for sustenance. It also carries emotional and spiritual values that vary due to diverse cultural communities. The dietary habits within such a wide group and the cultural values of eating specific EF species on specific calendar promote the conservation and sustainable use of these species. Therefore, the preservation and sustenance of biodiversity are ensured.

Food and medicine continuum links tradition and modern application

In the past, EFs were consumed due to their perceived medicinal attributes [16]. Flowers have served as effective agents in traditional Chinese medicine and ethnomedicine, aiding in matters of beauty, blood circulation, mood modulation, and even sleep enhancement [45]. The Compendium of Materia Medica, a comprehensive collection of 52 volumes of materia medica up to the sixteenth century, includes 26 volumes of botanical medicines, of which more than 80 types are flower medicines, accounting for one-tenth of all botanical medicines [46]. In the 2020 edition of Chinese Pharmacopoeia (Volume I), there are 27 flower drugs with the utilizable parts including bud, stigma, inflorescence, receptacle, pollen and intact flower. They are effective at clearing heat, stopping bleeding and promoting blood circulation for removing blood stasis. They have pharmacological effects in the clinical treatment of skin diseases, gynecological diseases, psychiatric diseases and cardiovascular diseases [47]. We also investigated some of the flowers sold in the Xishuangbanna market for medicinal purposes only. Such flowers include Prunella vulgaris and Leonurus japonicus. They are commonly used as medicine by the local people, but we excluded them from Table 2.

The homology of medicine and food is a part of the traditional culture of various linguistic groups in Xishuangbanna. A total of 95 species belonging to 43 families were identified and summarized [28]. In this study, 179 EFs (84.4%) with medicinal functions were surveyed, much more than other functions. In Xishuangbanna, people possess an extensive range of knowledge concerning medicinal and edible plants, marked by unique ethnic and regional attributes. This knowledge plays a significant role in their daily lives.

The interconnection between food and medicine is a prevalent occurrence observed globally, rooted in ancient cultural practices. The traditional knowledge and wisdom of the food and medicine continuum were critical for people in the past to improve health and defeat diseases. Nowadays, they can provide raw materials and relevant information for healthy food and drugs [48]. The list of substances traditionally used as both food and herbal medicine published by the Chinese authority covers 109 food-medicine dual-use entities, 15 of which are derived from flowers [49]. Most of the medicinal and dietary plants documented in this study are not included, which indicates the potential to scout and research them. The medicine and food homologous flowers link traditional culture and modern applications, deserving much attention and far-reaching research.

Edible flowers for sustainable development in the future

The utilization of flowers as food is not a recent revelation, yet it often goes unnoticed. Conventionally, flowers, predominantly appreciated for their ornamental appeal, are typically employed for decorative or landscaping purposes in the majority of people's perception [8, 14, 50]. Even in catering, flowers serve to enhance sensory pleasure through their appearances and aroma, though they are often perceived as inedible [9]. In China, the culture of flowers is characterized by the ornamental function and various beautiful implications [51]. Eating flowers is always on the edge of the culture and food system, existing in the rural and indigenous foodscape in China [52]. Among the urban populations, the concept of flower-eating culture is relatively novel, drawing attention due to its unique ability to provide both nourishment and spiritual enrichment to humanity. It also offers a fresh perspective in contrast to consuming leafy vegetables, presenting the potential to contribute to a health-conscious way of living.

The nutritional, phytochemical and pharmacological studies on some representative EFs in Xishuangbanna partly justify the use of EFs by local people and reveal their potential to be exploited. The flower of Gmelina arborea is rich in nutrition with various amino acids, minerals, sugars, fiber and trace elements such as selenium. It also has excellent hypoglycemic and antibacterial activity [53]. Pigment extracted from it has good properties and is non-toxic and odorless [54]. Musa acuminata inflorescence has high total phenolic content with significant free radical scavenging activity and good antioxidant capacities [55]. Buddleja officinalis inflorescence contains flavonoids, phenylethanols, terpenoids, alkaloids and volatile oils, which have a variety of pharmacological activities such as antioxidant, antibacterial, anti-inflammatory, neuroprotective and immunomodulatory [56]. The cake made from G. arborea flowers was a widespread delicacy, easily accessible in markets. It held great significance as a staple during the Dai New Year celebration, known as the water splashing festival. During its preparation, Dai women combined dried flower powder (referred to as Maisuo in Dai language) with glutinous rice powder, brown sugar or white sugar, sesame seeds, peanuts, and vegetable oil. The amalgamation was then shaped into cubes, enveloped in banana or Phrynium leaves, and steamed in a wooden pot. This steamed cake, called Khaonuosuo by the locals, could be stored at room temperature for around a week due to the bioactive properties of Maisuo, which exhibits antibacterial effects [38, 39].

In fact, studies on the factors influencing consumers’ attitudes toward the EFs’ consumption showed that health benefits are not the most important reason why people consumed EFs [57]. The cultural factors and specific curiosity have great influences on attitudes toward the consumption of EFs according to the survey in three different countries (Portugal, Slovenia, and Brazil), respectively [57], and in Taiwan of China [58]. Whatever the motivation, it is no doubt that there is a huge market for flower-eating to be explored. A questionnaire survey conducted in Portugal, where there is little flower-eating culture, showed that flowers can be popular in gastronomy [59]. As an unfamiliar food in South America, consumers showed a positive attitude to food with flowers either for eating or for decoration [60].

The local farmers’ markets as well as supermarkets provide EFs and derivative products as bridges linking EFs with consumers. The consumption of flowers holds significant importance in the diet of individuals residing in Xishuangbanna. This flower-centric culinary culture has consequently led to the development of associated products. Within local supermarkets, canned pork products are specifically labeled as 'suitable for preparing Musa inflorescence' on their packaging. The potential of the EF market lies not only in the development of food and drug products based directly on EFs as materials. It lies also in the creation of more derivative products in the whole EFs knowledge system based on a common perception and a wide range of users.

Though the EFs market has become increasingly promising, toxicity treatment is an issue to be raised [9]. Various toxic and anti-nutritional constituents, including trypsin inhibitors, hemagglutinins, oxalic acid, cyanogenic glycosides, and alkaloids, have been detected in the floral structures[8]. In this study, 29 EFs (13.7%) should be pre-processed by boiling or blanching in hot water, or removing peels and some parts before cooking and eating. Although the locals do not know the exact toxic ingredients, they have traditional knowledge to ensure their safety. Toxicological studies on these EFs can identify specific toxic components or discover novel toxic components that will contribute to consumption safety.

Chinese food is now shifting from traditional cuisine toward more meat and processed foods [61]. It is time to pay attention to healthy eating including the plant-based dietary trends worldwide [62]. Research has established the advantages of plant-based diets for China’s aging population [63]. Combining plant-based food with local production would be an advantageous approach [64], suggesting that EFs could play a substantial role in enhancing the local food system and providing potential solutions to societal challenges such as aging and health-related concerns.

Conclusion

Through the ethnobotanical survey, 212 species and varieties of edible flowers from 58 families along with a variety of related traditional knowledge in Xishuangbanna were recorded and summarized. Local people are knowledgeable about which EFs are safe when consuming, how to process them by removing toxicity or bitterness, and whether they can be cooked with other parts of the plant. The traditional knowledge on usage of EFs is the main and representative element of flower-eating culture, but it is gradually diminishing. The preservation and further scouting of traditional knowledge of edible and medicinal flowers are critical because of their biocultural significance and great potential for markets, scientific research and industrial exploitation. The practice of consuming flowers, rooted in local traditions, serves as a bridge between tradition and modernity. This flower-eating culture has the potential to promote the conservation of biocultural diversity, healthier food systems and sustainable development in the future. As such, policymakers are able to consider initiatives to support the documentation, conservation, and revitalization of this cultural heritage, recognizing its potential benefits for both local community and broader societal contexts.