British spelling: to study plants in their natural habitats; to collect plants for scientific study.
From 'botanic' plus the verb-forming suffix '-ize/-ise.' The British spelling preserves the 's' which is standard in British English for the '-ize' suffix (though both are acceptable in British English).
Darwin and other Victorian naturalists would go 'botanising' in the countryside and bring home specimens. It's this wonderful word that captures the idea of wandering around nature like a detective, looking for plants and collecting them for study.
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