Cacti are amazing organisms. They live in the most challenging environments and continue to survive. The Cactus family diverged from other related plants about 35 million years ago. Interestingly, most species are from the New World of the Americas. Asia and Africa's Mistletoe Cactus (Rhipsalis baccifera) is the one exception.
You may think that cacti could live very long under desert-like conditions. Indeed, drought is a regular occurrence in many of their habitats. Trees are among the oldest living plants, with some colonies existing for thousands of years. The oldest tree resides in the White Mountains of California, estimated at 5,062 years old.
Cacti are a different story. Scientists believe that most species live about 20 years. However, there are some hardier members of this family. Saguaros can make it up to 200 years. The Fishhook Barrel Cactus (Ferocactus wislizenii) also has a long lifespan of up to 100 years. The Totem Pole Cactus is another species that is equally as long-lived. You may wonder how they can live in such dry places.
Living in an arid environment poses several challenges. Preventing water loss is imperative. Cacti have several unique adaptations, starting with their structures. They belong to a group of plants called succulents. Instead of relying on the weather to provide enough water year-round, they store it. That explains the fleshy pads and trunks.
Cacti slow evaporation with a thick waxy outer layer that minimizes water loss. Plants exchange moisture with the air around them. They take in carbon dioxide and give off oxygen through openings in their leaves called stomata. Usually, it occurs during the day when photosynthesis is happening. Cacti conduct gas exchange at night to reduce evaporation and conserve water.
Probably the things that people associate most often with cacti are their needles or spines. It’s another way that these plants reduce moisture loss. Otherwise, animals would feed on them and pierce their protective outer layer. All of these adaptations give cacti an evolutionary edge to survive as long as they do.
On the flip side of the coin, cacti don’t fare well in wet conditions. They are shallow-rooted, allowing them to absorb water quickly when it rains before it evaporates. However, they lack the anchoring that roots would offer. Cacti are also susceptible to rot.
Cacti are excellent examples of plants that have made the best of their fate. They have adapted to live where other species would struggle, even the largest trees. Old Man Cactus is a lot tougher than anyone would guess.