Even without the bonus of delightful fruit, citrus would be popular landscape plants for their attractive form, glossy evergreen foliage, and headily fragrant flowers.
Your region's winter temperatures play an important role in determining what kinds of citrus you can grow. The more common types can be grown outdoors only in the southernmost parts of the United States (Zones 8, 9, 12-27). Lemons, limes, and citrons are generally the most sensitive to freezes; sweet oranges, grapefruit, and most mandarins are intermediate. Kumquats, satsuma mandarins, sour oranges, and calamondins withstand temperatures into the high teens. Hardy citrus, including citrange and 'Changsha' mandarin, are good choices for Zones 7, 28-31 (just outside the typical hardiness range).
Heat requirements also play a role in your choice of citrus. Sweet-fruited varieties need moderate to high heat to form sugars, while sour-fruited types require less heat.
All kinds of citrus trees are self-fertile.
Depending on species and variety, standard trees range from 6 to 30 feet tall and wide; dwarf and semidwarf sorts reach one-half to two-thirds the standard size.
Training and pruning
Train and prune citrus to shape as desired. In freeze-prone areas, don't prune in fall or winter.
Pests and diseases
Most citrus problems are minor and can be solved by improving growing conditions: give the trees adequate fertilizer, excellent drainage, and enough water to keep soil moist but not soggy. Slugs and snails can be a severe nuisance.