Do Cacti Have Roots?

Succulent Roots

• Many desert plants have succulent roots -- thick, fleshy roots that act like sponges to store large quantities of water. Only a few species of cacti share this feature. All of them are cacti with relatively small stems; cacti with larger stems require rocky soils for stability, and these rocky soils are unfavorable to the big roots a larger cactus would need if it were to rely on succulent roots.

Shallow Roots

• Most cacti have relatively shallow root systems. This is especially true of cacti that have hooked spines, because the shallow root system makes it easier for them to colonize new territory and disperse. If a passing animal accidentally tears up the cactus by catching the hooked barbs on its fur, for example, it may carry the cactus to a new location, where the cactus can take root and grow. A deeper root system would prevent the cactus from making use of animal transport in this fashion.

Water

• The most important benefit of shallow roots, however, is not dispersal but the ability to collect water. A widely spread root network lying just beneath the surface of the soil enables the cactus to take advantage of brief, occasional periods of rain. According to Dalhousie University's page on cactus biology, for example, one young saguaro cactus about 12 centimeters high was found to have a root system that spread across an area of soil 2 meters in diameter. Despite its impressive width, this root system penetrated a mere 10 centimeters in depth.

Taproots

• Larger cacti like saguaros need an anchor to prevent them from being torn up by desert winds. These cacti often feature taproots that bore their way straight down into the soil. The taproot may also enable the cactus to take advantage of water or nutrients deeper in the soil, assuming these are available. Like shallow root systems, taproots are just one more adaptation that help some species of cacti thrive in an unusually hostile environment.