Many older properties come with existing landscape trees that are hard to identify. This makes it difficult to decide whether to keep a given tree. Several common ornamental and fruit tree species including citrus species and some types of plums have thorny trunks and branches and produce yellow fruit. In some cases, fallen fruits and sharp thorns create a nuisance or safety hazard. Identifying the specific species helps homeowners more effectively plan their landscaping projects.
This familiar citrus tree produces sharp thorns on the twigs and grows to be 10 to 20 feet tall. The fruit is rounded, sometimes with a nipple-shaped protrusion on one end and is quite sour. Lemons are cold sensitive and are found only in warm climates, such as southern Florida, California, Texas and Hawaii.
Citrons produce large, oblong-shaped, yellow fruits with thick, fleshy peels. The tree is small, thorny and straggly. The fruit is inedible but decorative. One unusual type, the Buddha's Hand, splits into many fingerlike projections. Citrons are extremely cold sensitive and unusual in all but the hottest parts of the U.S.
Pummelo trees produce the largest citrus fruit in the world and are one ancestor of the grapefruit. Their yellow-to-green fruits contain white or pink flesh and are sweet or extremely sour. Like other nonhybrid types of citrus, pummelo trees sport sharp thorns. These plants prefer warm climates and do best in the hottest parts of the U.S. where frost is not a danger.
These tiny citrus fruits may be yellow to bright orange in colour and grow on a small, shrubby trees with infrequent thorns. Kumquats often grow in containers but can live outdoors in warm climates. They fruit in November and go dormant in cold weather.
Also called hardy orange, this ornamental tree is among the most cold hardy of citrus. It produces yellow, ball-shaped fruit containing many seeds and a little, very sour pulp. Technically edible, this fruit is rarely eaten raw by humans, but it can be processed into marmalade or candied. Trifoliate oranges have very thorny trunks and branches and are used as rootstock for more delicate citrus trees.
Sour oranges were among the first citrus introduced to the Americas and quickly naturalised in subtropical and humid tropical regions. Their fruit is edible but is usually made into marmalade. Sour orange is often used as rootstock for other trees. These trees are hardier than other oranges and produce a small fruit with a yellowish peel. Sour orange trees have long spines on their branches.
Some plum species, including Prunus Americana, sport spines along their branches. The American plum, also called wild plum, produces sweet flowers in spring. In the summer, it sports red-to-yellow fruit that is sweet when ripe and has a high pectin content. The American plum is hardy throughout much of North America and grows even in rocky or infertile soils.
This European native is often planted as an ornamental tree in North America due to its purple or red foliage. Cherry plums grow to 15 to 25 feet high and have a rounded shape. Its fruits resemble cherries but are larger and may be red-to-yellow or purple in colour. The cherry plum sports long spines on the branches.
- Purdue University; Lemon; Julia F. Morton; 1987
- University of Arkansas; Hardy Orange or Trifoliate Orange; Gerald Klingaman; Feb. 9, 200
- Ohio Department of Natural Resources: American Plum
- University of Illinois Extension: Cherry Plum
- AgriLife Extension Texas A&M System; Home Fruit Production-Miscellaneous Citrus; Julian W. Sauls, Ph.D.; Decmber 1998