Why do cacti have spines?
Quick Answer
Cactus spines are modified leaves that defend the plant from animals, reduce water loss, provide shade and can even help collect moisture.
The Full Story
Cacti evolved in hot, dry environments where large flat leaves would lose too much water through evaporation. Over time their leaves became spines, while the green stem took over photosynthesis and water storage. Spines deter thirsty animals from biting into the water-filled stem. Dense spines also trap a layer of still air and cast shade, keeping the surface cooler and cutting water loss. Spines grow from special cushion-like structures called areoles, which are found only in the cactus family.
Key Facts
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Suggested video title for this topic:
"A cactus is a plant that turned its leaves into needles — here's the desert survival logic behind it."