We have several citrus trees including orange, tangerine, lemon, lime, kaffir lime, and loquat, but we noticed only some of them have thorns. I looked it up online, but there’s not much information out there. So, I did some research to find out more. Here’s what I found.
Citrus trees normally have thorns as they evolved with them to defend against browsing herbivores and to retain water. Only a few varieties such as Eureka lemon and Persian lime were bred to have little to no thorns. Citrus tree thorns aren’t poisonous and don’t need to be removed.
So, why do citrus trees have thorns in the first place, and which ones have them? Let’s take a closer look.
Why Do Citrus Trees Have Thorns?
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.
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 tree, especially when the plant is younger. Additionally, citrus trees evolved thorns as a way to retain water in dry regions.
Once the plant grows bigger and stronger, it can better protect itself from predators and it stops producing as many thorns.
Thorns can also retain water to some degree. They do this by trapping moisture and dripping around the plant as a slow, but constant source of water.
So, how exactly do these thorns form?
Thorns are actually branches that the tree modifies to end at a point through the use of stem cells (source). Rather than making a branch, the tree has the cells make thorns.
But not all citrus trees produce thorns. Let’s take a closer look at the ones that do (and the ones that don’t).
Which Citrus Trees Have Thorns?
|Thorny Citrus Trees||Thornless Citrus Trees|
|Mandarin Orange||Eureka Lemon|
|Navel Orange||Persian Lime (Tahiti Lime)|
|Blood Orange||Fallglo Tangerine|
|Meyer Lemon||Dancy Tangerine|
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.
Here are some of the most common citrus trees with thorns:
- 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 (source).
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 citrus tree’s 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 complications such as infections if the wound is handled improperly.
Although the thorns on citrus trees aren’t poisonous, the oil from the leaves is known to occasionally cause 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 wounds 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 and protect against predators, 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.
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.
To see how to best prune citrus trees, check out my other post here.
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!
My Recommended Citrus Fertilizer
There are SO many citrus fertilizers out there, so it’s difficult to know which one to choose.
Generally, it’s best to look for:
- Quality ingredients
- Reputable brand
Plus, citrus trees prefer double the nitrogen to other ingredients. This means an NPK (nitrogen, phosphorus, and potassium) ratio of 2:1:1.
Because of this, I prefer Down to Earth’s Citrus Mix. It has an NPK of 6-3-3, so it’s a great choice for citrus trees. It’s made with quality ingredients and my citrus and avocado trees absolutely love it.
If you’d like more information about the best citrus (and other fruit tree) fertilizers, check out my post below.