When you think of orange trees, what comes to mind? Sweet citrus fruit, right? Not so fast! Some orange trees have thorns. But what kinds of orange trees have thorns – and why?
The most common orange tree with thorns is Trifoliate orange, an ornamental hedge species that produces tart, seedy fruits. These fruits aren’t used for raw eating but can be processed into marmalade. The thorns help protect the tree, with the thorny branches producing an attractive hedgerow.
Of course, the Trifoliate orange isn’t the only thorny orange tree. There are plenty of other citrus trees that produce thorns as well. Let’s take a closer look!
What kind of orange trees have thorns?
Some of our favorite plants grow with thorns. The combination of their beauty, fragrant aroma, yummy flavor, and spiky exterior is indeed an interesting sight to behold.
Most but not all citrus fruit trees grow with thorns. When talking about citrus fruits with thorns, it’s good to know how they are organized. Citrus fruits fall into seven categories. There are oranges, mandarins, grapefruit, pomelos, limes, lemons, and tangelos.
The most common type of orange tree with thorns is Trifoliate orange (Poncirus trifoliata). It develops a web of thorny branches that create natural barriers, making this plant a prime candidate for growing an ornamental hedge. The fruits of this orange tree don’t taste the best, so it’s not commonly grown for the fruit.
Many citrus trees develop thorns at the nodes. As a citrus tree matures, it may outgrow its thorns. Most lemon (Citrus limon) varieties have thorns. However, the ‘Eureka’ variety is thornless.
There are also thornless varieties of limes. However, the thornless types are thought to be less productive, less flavorful, and less desirable. The most well-known lime (Citrus aurantfolia) is the ‘Mexican lime’ or ‘key lime.’
The ‘Marsh’ variety of grapefruits has short flexible thorns. It is the most sought-after variety globally because it has the sweetest flavor and the least amount of seeds.
Kumquats are also popular citrus fruits. However, after 1915, they were reclassified into the Fortunella genus. We love kumquats for their sweet and tangy flavor, edible skin, and convenient size. The ‘Hong Kong’ variety of kumquat also is heavily covered in thorns. However, the ‘Meiwa’ variety does not have as many thorns.
Why does my orange tree have thorns?
Orange trees have grown to develop thorns for many of the same reasons animals like porcupines have thorns– to protect against predators. In other words, thorns are like anti-herbivore defense mechanisms.
The vegetation on young fruit trees is incredibly delicate. That is why many juvenile specimens of orange trees have thorns. On the other hand, mature specimens often do not have thorns.
Thorns are branches that the tree modifies to end in a spikey point. So instead of the tree telling the new growth to grow into a branch, it tells it to grow into the shape of a thorn.
Citrus tree thorns are not poisonous and do not contain toxins or harmful compounds. Although not toxic, citrus tree thorns can cause skin irritation and rashes if mishandled.
We always recommend wearing long sleeves and gloves when working with citrus trees. If you do get scratched by one of the thorns, clean the wound carefully because all the other dirt from your garden might cause an infection.
Do all orange trees have thorns?
Not all orange trees have thorns. In fact, there are some ornamental orange trees that grow without thorns.
Ornamental orange trees were first cultivated in 2400 B.C in China. Later, they were brought to other parts of Asia, Europe, and Africa.
They were traditionally grown in greenhouse-like settings called ‘orangeries’. For that reason, ornamental orange trees are well-adapted to living in containers. They can easily be grown on patios, walkways, porches, and garden settings.
Ornamental orange trees may take up to five years to bear fruit. Pruning ornamental orange trees is extremely important to encourage proper growth and to let in light and air.
Do Navel orange trees have thorns?
By themselves, navel oranges (Citrus sinesi) grow on thornless trees. However, navel orange trees are often grafted onto rootstocks that do have thorns.
Navel oranges are grafted onto rootstocks of different orange varieties to boost their cold tolerance, increase disease immunity, and restrict their growth. The Trifoliate orange is the most common rootstock that navel oranges are grafted onto.
The Trifoliate orange is a more bitter and sour orange, but it has a harder cold tolerance. Plus, the branches and stems of Trifoliate oranges have thorns to protect the tree from pesky predators. The Trifoliate orange variety has thick two-inch-long thorns.
Do mandarin trees have thorns?
Yes, Mandarin orange trees have thorns. The thorns are most prominent before the orange tree begins bearing fruit. Typically, orange trees that are grown from seed have the most thorns. On the other hand, orange trees grafted onto an adult tree with fewer thorns can grow to be thorn-free.
Varieties of citrus fruits that are considered to be ‘thornless’ may not be completely thorn-free. Instead, they often just have much fewer thorns.
Do valencia orange trees have thorns?
Yes, Valencia orange trees are grown with thorns. These orange trees grow blunt-shaped, slender, and flexible branches. Because they taper at the ends and become pointy, they are considered to be thorns.
Because thorns are considered branches, they are technically part of the tree’s vascular system. Besides protecting against herbivores, it is thought that the presence of thorns in some orange varieties is attributed to drought resistance because thorns tend to be more prevalent in regions with arid conditions.
Do tangerine trees have thorns?
Yes, tangerine trees have thorns. However, there are some varieties of tangerine trees that are thornless. The most common thorn-free tangerines are the ‘Fallglo’ and ‘Dancy’ varieties.
Thorns on tangerine trees can be pruned off. Pruning the thorns on a citrus tree will not damage the tree. But ideally, the thorns should be removed from the rootstock when the tree is grafted. Mature trees tend to have fewer thorns can juvenile trees.
When working with tangerines, you can protect yourself by wearing gloves, being vigilant for thorns, and using a long-handled fruit picker during your orange harvest.
Final thoughts
Citrus trees grow thorns in order to protect the young plant from predators who might want to snack on the fruit and ruin the plant. Thorns also grow to hold more water in drought-stricken areas of the globe.
Suppose the original orange variety does not grow thorns by itself. In that case, it is often grafted onto a rootstock variety that grows with thorns to boost its defenses against predators. On the other hand, oranges are sometimes purposely grafted onto rootstocks that do not possess thorns.
Thorns on orange trees may add a few obstacles when you want to harvest, but having thorns grow on orange trees is ultimately a good thing. Just remember your gloves and work carefully.
