Lemon trees reach an impressive height for a cold hardy tree. How big a lemon tree grows -- both height and width -- depends on the tree type, climate and gardening care provided. With over 200 lemon tree cultivars or types, trees vary in size.
True lemon trees -- those that are not hybridized or grown in dwarf sizes -- reach 10 to 20 feet tall at full maturity. Dwarf size lemon trees grow 4 to 5 feet tall when grown in containers, such as pots or half wine barrels.
The tree's alternate leaves, which are slightly reddish when young, are oval-shaped or elliptical, and around 2 1/2 to 4 1/2 inches long. Lemon fruits, when fully ripe, are oval, with a nipple apex on both ends and usually 2 3/4 to 4 3/4 inches long.
The lemon tree's root system depends on how the tree was planted. For example, according to the University of Florida Horticulture Extension, trees planted closer together often develop bigger, deeper root systems, below 12 inches in the soil. In spread, citrus roots have been detected up to 46 feet away from the tree trunk in a wild 44-year-old rough lemon tree.
Because dwarf-size citrus root systems are smaller, gardeners who want to cultivate dwarf lemon trees, for example, can plant more seeds per acre because each tree needs less space to spread.