While this year’s survey won’t be released until the summer, Dave Whitinger, the N.G.A.’s executive director and owner of Victory Seed Company, expects a similar trajectory based on the last five years of data. Although buying online is still a small slice of the total lawn and garden category, compared to buying in person at home centers, he said that leaves room for growth. “The spending-per-household growth rate outpacing the participation growth rate tells us the people who are buying online are increasingly comfortable putting more of their garden budget there.”