Keyword analysis (TF-IDF analysis)
This study divided 5,011 cases of data for 4 years from January 1, 2018, extracted with balcony vegetable garden as a keyword, into 2 years before the outbreak of COVID-19 (Jan. 1, 2018–Dec. 31, 2019) and 2 years after the outbreak (Jan. 1, 2020–Dec. 31, 2021), calculated TF-IDF values, and came up with the main keywords. TF-IDF gives weights to simple frequency to represent how much weight it has within a document, thereby enabling users to identify the importance more accurately (
Kwak and Kim, 2019).
Table 1 shows the keyword analysis results of the top 30 TF-IDF values of the two groups before and after the outbreak of COVID-19, excluding the search keyword 'balcony vegetable garden'. First, before the outbreak of COVID-19, the keyword showing the highest importance was seedling (1432.33), followed by lettuce (1302.14), harvest (1224.23), vegetable (838.93), and seed (763.89). During COVID-19, the keyword showing the highest importance was harvest (2090.19), followed by vegetable (1825.06), healing (1797.66), my place (1434.12), and hobby (1318.74). The words ranked at the top can be seen as keywords representing the public awareness or behavioral characteristics toward balcony vegetable gardens.
For the top 30 keywords before the outbreak of COVID-19, words such as flowerpot (744.26), child (633.08), fruit (621.64), kidney bean (612.44), experience (610.39), school (555.74), Arbor Day (555.42), and day care center (525.15) showed that balcony vegetable gardens are created through institutions carrying out home gardening programs and experience activities.
Keywords derived newly after the outbreak of COVID-19 compared to before were urban farmer (1235.64), mother (1175.50), kit (1116.82), pet plant (1097.83), stay at home (947.97), self-sufficiency (823.06), COVID-19 (813.51), and Daiso (756.16). These words implied that home gardening began to receive attention as a healthy hobby with people spending more time at home due to COVID-19 and that people are healing themselves by participating in balcony vegetable gardening with kits that are easy to purchase at stores selling daily necessities like Daiso.
Topic modeling
This study conducted topic modeling (
Kim and Kim, 2020), which is effective in summarizing a large amount of text data by forming a cluster of words in a document set to understand the main topics and inherent meanings of posts related to balcony vegetable gardens. First, the coherence of topics was measured, with higher coherence scores indicating that each topic has coherence (
Kim and Kim, 2019). In this study, the coherence index was highest at 0.356 when there were 4 topics before the COVID-19 outbreak, and it was highest at 0.493 when there were 5 topics during COVID-19, based on which this study conducted the analysis by selecting the optimal number of topics (
Fig. 2). Next, 10 keywords were derived for each of 4 topics before COVID-19 and 5 topics after COVID-19, giving name to each topic (
Table 2).
The results of naming the four topics before the outbreak of COVID-19 are as follows. Top keywords of Topic 1 included 'vegetable', 'lettuce', 'cherry tomato', 'crop', 'perilla leaf', 'sprout', 'cultivation', 'kind', 'urban agriculture', and 'taste'. These words helped identify the trend of cultivating various kinds of leafy vegetables through balcony vegetable gardens as part of urban agriculture. Accordingly, Topic 1 was named 'main crops of balcony vegetable gardens'.
Top keywords of Topic 2 included 'flowerpot', 'kidney bean', 'experience', 'soil', 'weekend', 'seedling', 'education', 'child', 'day care center', and 'school', which showed the institutions in which horticultural experience took place as well as the contents of such activities. They also confirmed that horticultural activities continued from educational institutions to home. Accordingly, Topic 2 was named 'gardening experience and inflow path of home gardening'.
Top keywords of Topic 3 included 'seed', 'herb', 'weed', 'sharing', 'preparation', 'flower', 'germination', 'fertilizer', 'bug', and 'repotting'. These keywords represent horticultural activity itself, proving that users were actively participating in home gardening activities such as seeding on the apartment balcony, weeding or removing bugs, and repotting. Moreover, these words showed the trend of sharing a set of procedures for balcony vegetable gardening activities. Accordingly, Topic 3 was named 'balcony vegetable gardening activities'.
Top keywords of Topic 4 included 'raised garden bed', 'apartment', 'set', 'rooftop', 'harvest', 'compact', 'salad', 'shelf', 'space', and 'recycling', which showed the types of vegetable gardens preferred by those participating in balcony vegetable gardening activities. They were mostly creating balcony vegetable gardens in compact space using raised garden bed sets or flowerpots. In addition, balcony vegetable gardens using various recyclables such as 'PET bottle' and 'Styrofoam' were also receiving attention. Accordingly, Topic 4 was named 'types of balcony vegetable gardens'.
The results of naming the five topics during the outbreak of COVID-19 are as follows. Top keywords of Topic 1 included 'my place', 'COVID-19', 'daily life', 'stay at home', 'healing', 'first time', 'hydroponics', 'nature', 'indoor', and 'vegetable'. Due to continued social constraints caused by COVID-19, balcony vegetable gardening at home became a part of daily life, through which people were healing themselves. Accordingly, Topic 1 was named 'daily life and home gardening during COVID-19'.
Top keywords of Topic 2 included 'green', 'raised garden bed', 'organic', 'sustainability', 'seedling', 'apartment', 'climate action', 'distribution', 'sprout', 'seed', 'and environment'. These words show the trend of sharing organic food people grew themselves, as well as the trend of aiming for environmental practices and sustainability such as climate action. Accordingly, Topic 2 was named 'balcony vegetable gardens and environmental practices'.
Top keywords of Topic 3 included 'fun', 'weekend', 'plant butler', 'gratitude', 'vitality', 'joy', 'mind', 'growth', 'expectation', and 'success'. They expressed the emotions and feelings people get from balcony vegetable gardening. In particular, there were many words expressing positive emotions, which showed the emotional support that people obtain from home gardening activities. Accordingly, Topic 3 was named 'balcony vegetable gardens and emotions'.
Top keywords of Topic 4 included 'urban farmer', 'mother', 'basil', 'Daiso', 'green onion', 'challenge', 'posting', 'kit', 'interest', and 'food'. These words showed interest in food and how people began to find interest in balcony vegetable gardens through family or posts and actually attempting to participate in horticultural activities by raising seeds or seedlings purchased at a store selling daily necessities. Accordingly, Topic 4 was named 'inflow path of balcony vegetable gardening activities'.
Top keywords of Topic 5 included 'self-sufficiency', 'beginner', 'health', 'creation', 'pet plant', 'harvest', 'flowerpot', 'picture', 'hobby', and 'recommendation'. This showed the trend that balcony vegetable gardening is receiving attention as a hobby for a healthy life, and the trend of new words like pet plant as well as interest in the activity. Accordingly, Topic 5 was named 'balcony vegetable gardens and hobbies'.
The results above imply that balcony vegetable gardening activities were encouraged and received attention as a type of urban agriculture before COVID-19, while after COVID-19 they are established as activities for healing, emotional support, environmental campaign, and hobby, and that this therapeutic effect and expected outcome may be a significant key to the promotion and development of urban agriculture. In particular, taking care of plants through home gardening like balcony vegetable gardens affects emotional changes such as sense of achievement, self-esteem, and security, thereby promoting individual welfare and environmental benefits (
Park and Shin, 2021;
Harding et al., 2022).
Among urban agriculture, balcony vegetable gardening activities have the advantage of enabling people to cultivate crops at home without moving, check the growth, have fun, and tend the vegetable garden regardless of time and place (
Kim and Yoon, 2016). The revitalization of urban agriculture based on these advantages is considered to be a solution to the social problems derived from the public health crisis caused by the infectious disease called COVID-19. Furthermore, it can be inferred that balcony vegetable gardens will become more popular as there is a growing interest in safe food supply and environmental practices through self-sufficiency.