Whether for their blossoms or their colourful fruit, citrus trees have long been in popular use as ornamental trees with gardeners and landscapers. Ornamental citrus trees are quite often dwarf citrus trees, purposely cultivated to remain small. Citrus can only be planted outdoors in sunny southern climates like California and Florida, but dwarf citrus can be kept in large pots or tubs and grown indoors, if necessary.
Mandarin Orange (Citrus reticulata)
The mandarin orange exists in hundreds of varieties (or "cultivars"), which include clementines, tangerines and many others. Mandarin orange trees grow naturally to 15 or 20 feet tall, although ornamental or dwarf varieties typically grow 8 to 10 feet in height. They produce white blossoms in the early spring and yield their fruit in November and December. One of the most popular of the mandarin varieties is the Owari Satsuma Mandarin, first cultivated in Japan; it is considered the hardiest cultivar of mandarin orange, more resilient in colder weather or dry conditions than other related varieties.
Meyer Lemon (Citrus x meyeri)
Widely believed to be a cross between a true lemon and a mandarin orange, this tree was introduced to the states in 1908 by an agricultural explorer named Frank Meyer. It is another variety of cold-hardy citrus, known for its aromatic blossoms and for yielding a sweeter, less acidic lemon than its "true lemon" counterparts. Growing to about 15 feet naturally (and smaller for dwarf/ornamental varieties), these trees yield abundant fruit when properly cultivated. Once banned as a species in some places due to a plant virus it was known to carry, today most Meyer Lemon trees are the "improved" variety, derived from a virus-free clone discovered in the 1950s.
Key Lime (Citrus aurantifolia)
Also called Mexican lime, this tree grows more as a small, thick shrub, growing naturally between 6 and 13 feet. Its blossoms are typically white, occasionally with light purple tips, and its fruit is oval shaped, aromatic and pale yellow. Key lime trees are thorny and should be handled with care; they are also less cold-hardy than other citrus, and should be grown indoors where temperatures can dip below -1.11 degrees Celsius.