This study used electromyographic analysis to investigate specific upper limb and hand muscle activation during 15 common horticultural activities. A total of 30 Korean adults between the ages of 20 and 30 years, with an average age of 24.8 years, were recruited from Konkuk University, Seoul, South Korea. Electromyographic measurements were made using a portable four-channel electromyograph. Bipolar surface electromyography (EMG) electrodes were attached to six upper limb muscles (i.e., upper trapezius, triceps—long head, biceps brachialis, flexor carpi ulnaris, flexor carpi radialis, and brachioradialis) and two hand muscles (i.e., thenar eminence and hypothenar eminence) on the dominant hand. These eight muscles that were selected play a major role in the operation of upper limbs and hand muscles for upper body low-impact activities. Each participant did the 15 horticultural activities on one occasion with two separate sessions. Each activity was performed for 60 seconds followed by a 15-second rest period sitting at a table on a height-adjusted chair between each activity. All eight muscles measured were used together during most of 15 horticultural activities. Upper trapezius, thenar eminence, and hypothenar eminence had higher muscle activity than the other muscles. Triceps—long head displayed very low EMG values compared with the other muscles. The EMG data will facilitate developing scientific and research-based gardening intervention and/or horticultural therapy programs for improving physical health and physical rehabilitation.