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Why Citrus Trees Have Thorns and Which Ones Have Them

We have several citrus trees including orange, tangerine, lemon, lime, kaffir lime, and loquat, but we noticed only some of them have thorns. So, why do citrus trees have thorns in the first place?

Citrus trees evolved to have thorns as a defense mechanism against herbivores. This protection method is necessary to stop any predators from eating leaves and fruit from the plant. Additionally, citrus trees evolved thorns as a way to retain water in dry regions.

Now that we know a bit about why citrus trees evolved to have thorns, let’s take a closer look at how citrus trees developed thorns and a few other questions you may have. Questions such as, “Which types of citrus trees have thorns?” and “Are these thorns poisonous or dangerous to gardeners?”. Read on to find out more!

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Why Do Citrus Trees Have Thorns?

a thorn on my potted meyer lemon tree

As mentioned, young citrus trees have thorns to protect the tender fruit and leaves from being eaten by any animals. Once the plant grows bigger and stronger, it can better protect itself from predators and stops producing as many thorns.

Thorns can also prevent trees from getting thirsty in dry areas. They do this by trapping moisture around the plant as a constant source of water.

But how exactly do these thorns form?

Thorns are actually branches that the tree modifies to end in a point through the use of stem cells. Instead of the tree telling the cells to keep growing and form a branch, it tells them to make a thorn.

But not all citrus trees produce thorns. Let’s take a closer look at which ones do.

Which Citrus Trees Have Thorns?

Citrus Trees With ThornsCitrus Trees Without Thorns*
Mandarin OrangeEureka Lemon
Navel OrangePersian Lime (Tahiti Lime)
Blood OrangeFallglo Tangerine
Meyer LemonDancy Tangerine
Lisbon Lemon
Key Lime
Mexican Lime
Kaffir Lime

*Keep in mind that the name “thornless” not only includes citrus trees with no thorns but also those with fewer thorns than average. So, even if you do get a “thornless” variety, there’s a good chance some of the branches will have a few thorns. In general, it’s rare for a citrus tree to be truly thornless as they have evolved to be this way over many years.

Citrus is one of the most popular fruits in the United States, with more than 200,000 tonnes harvested in 2019, so it’s fairly common to come across these thorny fruit trees.

Here are some of the most common citrus trees with thorns:

  • Lemon
  • Lime
  • Orange
  • Grapefruit
  • Kumquat
  • Tangelo
  • Mandarin Orange

Out of these, the most commonly planted are lemon, lime, and orange trees.

However, not all varieties of these fruits will have thorns.

Some types of citrus trees are specifically bred to have fewer or no thorns.

While lemon trees are included on this list, their thorniness also depends on the specific type of lemon. For example, Eureka lemons are practically thornless while the Lisbon variety has many thorns.

Many gardeners would prefer to plant non-thorny citrus trees to avoid getting their fingers pricked but this can’t always be avoided. So, what exactly happens if a thorn pokes you—are they poisonous or stinging like some other plants?

Are Citrus Tree Thorns Poisonous?

Citrus tree thorns are not poisonous and do not contain harmful compounds or toxins. However, even though the thorns cannot poison you, they can cause other medical problems such as infections if the wound is handled improperly.

Although the thorns on citrus trees aren’t poisonous, the oil from the leaves can cause rashes and skin irritation. You should still be careful around the thorns because they can scratch you. With all the dirt and plant matter in your garden, open injuries can lead to infection, so be careful!

Can You Prune Citrus Tree Thorns?

Citrus tree thorns can be pruned without much consequence. Ideally, thorns on citrus trees help accumulate water in times of drought, but if you live in a region that gets plenty of water, then there’s not much of a need for thorns on citrus trees.

However, if you frequently get visitors from herbivores, especially large ones such as deer, then it can be best to leave the thorns as a deterrent. Citrus tree leaves and fruit are an easy and tasty snack for many herbivores, so leaving the thorns on can definitely help keep your trees alive.

Still, if your citrus trees are mature and grown, and you’re not concerned about citrus tree predators or drought, then you can prune the thorns off without losing a benefit.

As you might have guessed—the best way to avoid getting hurt by citrus tree thorns is to get rid of them. Check out this video by IV Organic to find out more!