Bromeliads, with their handsome often mottled leaves and bold flower spikes, are prized houseplants, but in San Diego, these tropical perennials thrive outdoors as well. About one-third of the 1,500 species are “air plants” or epiphytes that survive growing on rocks or trees. Others hold water in leaf-based “cups” in between rains or watering. Most tolerate low light and competition from tree roots, which makes them ideal for underplanting in dry shade. One of the country’s major bromeliad growers, Kent’s Bromeliads, is based in Vista. To learn more about these plants, which include tillandsias, aechmeas, neoregelias, vrieseas, and desert-loving puyas, plan to attend the San Diego Bromeliad Society’s annual show and sale this month in Casa del Prado in Balboa Park. Details are at www.bsi.org/webpages/san_diego.html.