Cactus plants are unique in so many ways, one being their prickly appearance. Sure, there are plants like roses that contain thorns and sharp edges. Still, no other plant is completely covered head-to-toe in sharp needles like a cactus.
You may be wondering how cacti evolved into glorified pin cushions compared to other more approachable plants and succulents.
In this article, we answer the question – why are cacti prickly. We will discuss the benefits and functions of cactus spines and how they help cacti thrive in harsh desert environments.
What are Cactus Spines?
You may know cactus spines as “needles” or “stickers” in common terms. Did you also know that the spines are modified leaves? Over time, these structures modified from round leaves into sharp spines. It is hard to believe that at one point in time, cacti were a completely different shape than the plant we know and love today.
Benefits And Functions Of Cacti Spines
Biologically, there are several reasons behind why cacti grow spines, and how they help cacti stay healthy and strong. Below are the main reasons why cacti are prickly and cactus spines are crucial for each cactus to survive.
1) Cacti Spines Provide Shade
It might sound counterproductive to trade the shade of giant leaves for some skinny spines, right? After all, spines are way smaller than leaves, providing a tinier surface area of shade. It turns out that these spines are a more efficient form of shade than sending water and energy to hold up gigantic leaves in their place.
For example, think about how much energy it takes to hold up a heavy patio umbrella. If you switched it out for a smaller umbrella made for just one person, you may have a little less shelter from the rain or sun. However, your arms would also be much less tired. This is the trade-off of the cactus spines: maximum shade, minimum energy use.
The spines may not seem like they make much of a difference, but hundreds of lightweight spines can add up to plenty of shade.
2) Spines Protect Cacti from Predators
If there is only one thing to know about cacti, it is that they are unsurprisingly very painful to touch.
Cactus spines are mainly a result of the “survival of the fittest” evolution. For cacti to survive in the wild, they had to come up with a way to prevent animals from eating them.
Sharp cactus spines first acted as a barbed-wire fence to keep them safe from hungry animals. Clearly, this worked. In fact, cacti are planted around houses in Africa, used as natural alarm systems to keep away outsiders.
Grow Your Own Cactus
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3) Cacti Spines Reduce Evaporation
In the desert, every drop of water counts. Normal leaves may provide excellent shade but are lethal for desert plants due to just how much water they require. Think about earlier when we mentioned how cacti stay small and compact to save energy. By taking up a smaller surface area, energy and water are conserved in the arid heat. Spines also create a thin layer of fresh air around the plant, keeping the temperature lower.
4) Cacti Spines Aid Reproduction
Most likely, you live in an area where bees drink pollen from flowers and spread the plant’s seeds. In the driest and hottest areas of the desert, this normal pollination process cannot happen. Instead, cactus spines travel from place to place in the unlucky victim that gets stuck by them.
For example, an unlucky desert owl tries to perch on a cactus. The spines get stuck on their talons, and the owl quickly flies away in fear, with the spines still stuck on their feet. Cactus barbs take pieces of the cactus with them when they dislodge, which can regrow somewhere else. The spines and cactus pieces are also designed to travel long distances and still eventually regrow. So, when the piece of the cactus is dislodged, it can land somewhere and try to grow where it is dropped.
This process is great for cacti but bad for the owl (or any animal or human that becomes a host for their reproduction).
5) Cacti Spines Collect Water Through Condensation
Desert life means water is rare, evaporating as quickly as it first appeared. Surviving in the desert means becoming smarter about both collecting and storing water.
Luckily, cactus spines are one of their most efficient tools to collect water. A group of thin spines can form a net that traps in humidity, building up condensation between the cactus and the needles. It is similar to a closed lid terrarium, which traps foggy condensation inside. Just like how water runs down the sides of a foggy glass terrarium, the spine’s trapped moisture has nowhere else to go but down to the roots.
The process is truly ingenious, helping cacti brave long droughts.
Why are Cacti Prickly?
When seeing a large prickly cactus, most people only think about pain and staying far away.
Who knew that cacti had so many benefits of having spines! Hopefully next time you see a cactus, you can appreciate the journey taken from a struggling plant to a grown cactus that thrives in dry desert conditions.
Without their spines, cactus would have become extinct centuries ago, and it is hard to imagine a world without desert cacti to admire and enjoy.
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