"Tea" to the English is really a picnic indoors.

The line treats “tea” not as a mere beverage but as a social ritual. Calling it “a picnic indoors” emphasizes the English custom of turning an ordinary refreshment into a miniature occasion: a set time, a spread of small foods, and a mood of leisure and sociability. The comparison also hints at the way ritual can domesticate pleasure—bringing the informality and abundance associated with outdoor picnics into a controlled, interior setting. Read this way, the remark is both affectionate and lightly ironic, suggesting that cultural habits shape how people experience comfort, community, and even nature’s pleasures.