This study aimed to record and document medicinal plants and associated indigenous knowledge of the people in Kelala district northeastern Ethiopia. Kelala district is located in the south Wollo administrative zone of Amhara Regional State, which is 561 km far away from Addis Ababa. The geographical coordinates of the district lie between 100 28' N and 380 48' E (Fig. 1). The district has an altitudinal variation that ranges from 500–2300 m a.s.l. and it covers a total surface area of 143,433 ha . The study area has a unimodal rainfall with a long rainy period from June to October and small rain from March to May . The mean annual rainfall of the study area is 988 mm. The mean annual temperature of the study area is 17 0C ranging from the mean annual minimum of 6.2 0C to the mean annual maximum of 29.2 0C .
According to KDARDO , the dominant soil types occurring in the area are clay (17.4%), clay loam (0.6%) and clay to clay-loam (63.5%), loam to clay (0.7%) and silt clay (17.8%). Among these soil types, clay to clay-loam is the most abundant and suitable for cultivation of cereal crops. The vegetation of the study area belongs to dry single-dominant Afromontane forest and this type of forest is known to occur on the plateau of Tigray, Gonder, Wollo, and Harerge regions with an annual rainfall distribution between 500 and 1500 mm. The typical dominant species in the upper storey of these forests is Juniperus procera and Olea europea Subsp. cuspidata. Sometimes the juniper trees can be rather scattered and the forest is characteristic of Juniperus woodland with discontinuous evergreen undergrowth .
Based on the 2007 national population and housing census, Kelala district had a total population of 136,545 where 67,929 were men and 68,616 women. The majority of the people (94.4%) lives in the rural area by directly obtaining their means of subsistence from agriculture and associated activities while 5.6% of the people are urban inhabitants. More than 95% of the inhabitants were Muslims whereas 4% of the population practiced Christianity .
In the district, the major ten human diseases are dyspepsia, diarrhea (non-bloody), acute febrile illness, acute upper respiratory infection, infection of the skin and subcutaneous tissue, disease of the musculoskeletal system and connective tissue, pneumonia, urinary tract infection, helminths and trauma (injury, fracture, etc.). The most important livestock diseases in the district include sheep and goat pox, pasteurellosis (ovine and obivne), mange mites, blackleg, anthrax, African horse sickness, contagious eczema, lice, and fleas’ infection and rabies .
Site and informant selection
A reconnaissance survey of the study area was conducted from September 20 to October 10, 2017, and resulted in the identification of eleven study sites, namely Abet wuha, Lugama, Senbo, Kelela, Yimerina rebortu, Deger, Tirtira, Qorki, Aleltu, Gumero, and Mukech. These study sites were selected based on the presence of traditional medicinal practitioners and the recommendations of elders, kebele administrators, and health workers. Also, accessibility of the sites and agro-climatic zones of the district were considered to select the study sites (kebeles).
A total of 60 (41 males and 19 females) informants were selected from the population following Martin . Out of these, 40 general informants were selected randomly and 20 key informants were selected purposively based on the recommendations of knowledgeable elders, local authorities, and health workers by taking 1–2 individuals from each study kebele. The informants were aged between 20–91 years.
Qualitative and quantitative ethnobotanical data were collected from informants using a pre-prepared semi-structured interview method [21, 22]. Focus group discussion, participant observation, and guided field walk were also applied. Ethnobotanical data collection sheet was prepared in English and translated to Amharic language ahead of time to be used during ethnobotanical information retrieval from informants. Information was carefully recorded during an interview with an informant including local names of the medicinal plants, habitat of the plant, disease the plant treats, parts used, methods of remedy of preparation, ingredients added, dosage prescriptions, and routes of administration [21, 22]. Before data collection, written permission was obtained from the culture and tourism office of the district as well as permission from the local administration of each selected kebele. Following this, the purpose of the study was briefly explained to each informant and prior verbal consent was obtained.
Focus group discussion and guided field walk
Discussions were conducted to gather further information on medicinal plant knowledge at the community level, ways of transferring their knowledge, major threats on medicinal plants, and indigenous conservation practices. The method of guided field walk with the help of local guides from each study site was applied to make notes on the habit, habitat, morphological features, and association of the medicinal plants with other species. Moreover, it allowed seeing, smelling, and tasting the medicinal plants under investigation to understand the unique features of the species. The local field guides also played a crucial role in identifying the medicinal plants found in the field by proving their vernacular names. Voucher specimen collection was made from the wild and home gardens. Preliminary identification of the specimens was made at the field and the collected specimens were dried, pressed, and taken to the National Herbarium (ETH) in Addis Ababa University. Specimen identification was carried out by using taxonomic keys in the Flora of Ethiopia and Eritrea and comparing with authenticated specimens at ETH.
Ethnobotanical data were analyzed using basic analytical tools following Martin  and descriptive statistical methods such as frequency and percentage. Informant Consensus Factor (ICF) was computed to identify potentially effective medicinal plant species in the respective disease categories . Thus, where, ICF = informants consensus factor, nur = number of use citations in each category, nt = number of times a species used. Preference ranking and direct matrix ranking exercises [21, 24] were computed to recognize use-preference and/or use diversity of medicinal plants by the key informants. Values given by key informants on use-preference and/or use diversity of medicinal plants were added and ranked to get the outputs of the preference ranking and direct matrix ranking. The relative healing potential of each reported medicinal plant used against human diseases was computed as fidelity level (FL) . where Ip = the number of informants who independently cited the importance of a species for treating a particular disease and Iu = the total number of informants who reported the medicinal plant for any given disease .