Cactus spines are sharp. Really sharp. Cactus spines are modified leaves. Here is how the different sharp, pointy things differ:
- Spines are modified leaves, like what you’ll find on cactus.
- Thorns are modified branches or stems, like those found on citrus trees.
- Prickles are modified extensions of epidermal tissue. Roses have prickles, even though people typically call them thorns. The Fragrant Mimosa above also has prickles. Think of prickles as hairs. Sharp, pointy, painful hairs. See Sharp Points mean Protection
Scientists have come up with a lot of theories as to why cactus and other plants have sharp spines, thorns or prickles. Some of the theories explain spines as a protection against those animals that would eat the plant. Other theories include the fact that the spines shade the plant. Maybe it is a little of both. Imagine if this seed pod above were your finger.