Dwarf citrus trees add beauty and fragrance to sunny patios and decks—and they also produce flavorful fruits. Because most citrus trees are not cold hardy, many gardeners grow citrus trees in large patio containers that they display outdoors during the warmer months. Some citrus plants have fragrant blooms that perfume the air, and they're wonderful conversation pieces too. Dwarf citrus trees, like tangerine, lime and lemon trees, can be grown as houseplants indoors during the cooler months. When selecting the best citrus plants to buy online, consider their hardiness zone, growing requirements (most require full sun), the types of fruits they produce and their mature height and spread.