Interest in houseplants has exploded in recent years. But what causes floral trends, and prices, to grow? Zachary Crockett sows a few seeds. SOURCES:Justin Hancock, director of research and development at Costa Farms.Brian Williams, co-owner of Brian's Botanicals.Sarah Williams, co-owner Brian's Botanicals. RESOURCES:"Bidding Wars and $1,000 Succulents: The Wild World of Rare Houseplants," by Hannah Holland (The Washington Post, 2023)."Houseplants Boomed During the Pandemic. Gen Z and Millennials Say the Popularity Is Here to Stay," by Lucia Starbuck (KUNR, 2022)."The Most Iconic Houseplant Trends Through the Decades," by Wretched Flowers (Architectural Digest, 2021)."Meet the Plantfluencers," by Penelope Green (The New York Times, 2018).