All cacti have roots that carry out various essential functions for the plants such as holding cacti firmly in soil, absorbing water and nutrients, and storing food and water in the stem tissues of the plants. Morphology of cacti roots differs from extensive taproots to a web of fine roots that are closer to the soil surface and extend to a certain distance. If the roots are removed or are harmed or a stem is cut from a cactus, it can survive for some time and new roots grow from tissues near the base of the plant or cutting.
Do Cacti Have Roots?
Cacti do have roots and these roots group together to form root systems that are adaptations helpful for the plant in surviving hot, arid areas.
Cactus Root Systems
While growing different species of cacti, it becomes quite obvious that each species is unique, both in appearance and also in their roots.
- Many cacti have lengthy fibrous roots like the strands of hair.These roots are the extensive systems that spread laterally.
- In deserts, the roots are shallow, whereas in areas receiving more rainfall and at places where there is more competition for space, the roots go deeper in search of water and nutrients. Cacti like the barrel cacti have shallow root systems that are more dense to collect water droplets that fall from the cacti.
- The cacti survive on less water by absorbing water through its root system.
- Regular cacti will have both taproots and lateral roots.
- These roots, depending upon the nature of a cactus’s environment, can be especially huge, for example, with a cactus that is six-inch long, can have a six-foot long root system. These root systems are wider than they are deep and different types of roots forming the root system of cacti help them to survive in different environments.
Various Cactus Root Systems Are as Follows
Taproots
Many cacti develop a long, strong taproot immediately after germinating. A taproot holds a plant in rainstorms and goes deeper into the subsurface soil layers to absorb more moisture.
For Examples, columnar cacti like giant Mexican cereus (Pachycereus pringlei) and Saguaro (Carnegiea gigantea), both large, tree-like cacti of the Sonoran desert, have tap root systems.
Taproot of Saguaro grows deeper about 5 feet into the soil. Giant Mexican cereus is firm, having multiple branches that can be 50 feet tall. Saguaro is hardy, having a single or branched stem about 30 to 50 feet tall.
The enlarged, thick taproots of the small, Chihuahuan cactus Ariocarpus fissuratus wither during drought periods, pulling the above-ground part of the plant under the soil surface. It is a very slow growing cactus that can be grown in pots.
Lateral Roots
Cacti have lateral roots, besides taproots that branch frequently while growing. Cacti that lack taproots have lateral roots to keep them in place and to take food and water.
The lateral root system is more compact and near the surface, the roots branch out, often in a web-like pattern.
Saguaros have a large group of fine roots in the upper 3 inches of soil to quickly absorb moisture from even light rains. A young saguaro about 6 inches tall has a root system in a 6 1/2-foot area, extended more than 3 inches in the soil.
These two types of roots, taproots and lateral roots are generally found in large and small cacti. Most cacti have either one or the other type of root and a few cacti can have both, also depending on the atmosphere.
Specialized Roots
Sometimes taproot and lateral root systems are not suitable for some specific cactus plants, then certain specialised roots are developed for the plant.
The two types of specialized root systems are succulent roots and aerial roots.
Succulent Roots
As the name suggests, succulent roots are more apparent in cacti closer to the family of succulent plants. Cacti store food and water in succulent roots as well as in their stems.
Arizona queen of the night (Cereus greggii, formerly Peniocereus greggii), has an enlarged root system 5 to 60 pounds in weight. The enlarged section of the root is the secondary wood or xylem tissues that store starch and water. Succulent roots are not necessarily always present on succulent plants. These root systems are different from most other types as they not only transport nutrients to the major part of the cactus plant, but also provide long time storage of food and water.
For the cacti living in the desert areas, where food and water is scarcely available, this long-lasting storage is necessary for the survival of the plant.
As the succulent roots store a significant amount of nutrients and water, they are really heavy. It can be noticed while digging up a cactus with a succulent root system.
Weight of most succulent root systems vary anywhere between five pounds to 60 pounds depending on how complicated the roots are and how much storage the roots have accumulated.
Aerial Roots
Unlike the most underground root systems, aerial roots are seen above ground.
Aerial roots are white or sometimes even pink in colour, and grow on some epiphytic species of cacti that develop among tree branches.
Cacti having stems develop aerial roots and include Christmas cactus, Orchid cactus Ephiphyllum spp. and Hylocereus undatus. Aerial roots grow from the sides of the stems and grip the climbing cactus stems to the trees or rocks holding the plant just like squash vines anchor nearby surfaces while growing.
Aerial roots develop along with the normal roots that are below the ground. Orchid cacti are mainly grown for the large, brightly colored flowers of hybrid epiphyllums and night blooming cereus has large, white coloured flowers and bright-red, edible fruits.
Aerial root systems look like the branches of a tree and they sometimes are known as adventitious root systems.
Often, aerial root systems are used in affiliation with other rooting systems found below the ground, to protect the cactus; so that if a root falls off, the cactus remains alive.
Aerial root systems are helpful when there is very little rainfall to collect water, but are more useful when there is more humidity.
How Deep Are Cactus Roots?
Generally, cacti roots are not very deep. Let’s find out how deep cactus roots can grow:
- Cacti species that grow in deserts develop a shallow root system that absorbs rainwater before this water goes to the deeper roots of other desert plants, thereby becoming life-threatening to them.
- This is a simple strategy of Saguaro, the big columnar cactus of the Sonoran Desert. They usually germinate from seeds beneath the palo verde bush. As the cactus grows about four feet, it develops a root system that spreads to several feet in every direction, a few inches deep only.
- The saguaro can take the rainfall from a larger area with a widely spread root system like that, water that would have otherwise reached the palo verde bush. That bush will die soon and the strong, young cactus will have all the light and excess water to itself. Saguaros start growing fast when they are about four feet tall.
- Bigger species have certain kinds of taproot as well to provide the stability to go deeper into the soil.Cactus roots accumulate and conserve water in various ways.
- Some cacti like Prickly pears have shallow, extensive root systems that spread laterally 10 to 15 feet away from the plant. In short, rains that only soak a few inches of soil, the shallow roots aid the plant to absorb maximum water from a wide area.
- Cactus roots also change the traits as the water supply varies. Following the rainfall, existing desiccated roots become more water imbibing and new rain roots grow to assist in soaking up more water. During drought, the rain roots wither and fall off and the surviving roots dehydrate. As the existing roots shrink, it creates an air gap to avoid water in the roots from going back to the soil.
- Roots develop a corky layer to prevent water loss. This happens in the desert, but in a thickly planted garden when the water goes deeper down in quickly draining soil added in the garden, the roots can grow much deeper. As adjacent plants compete, roots grow deeper than wider to find water down there and stay there.
- Actually, we observe that they will go deeper till they hit the water table during winters and then they will degenerate back up to the drier portion of the soil, which tends to coincide with the depth to which you rectified the soil to make it fast draining.
- This will make them spend the initial part of spring growing new roots before starting to grow new branches. This cycle is repeated every year and you need to reform your soil much deeper to keep your cactus alive.
Note: Ensure that you have reformed your soil to be fast draining deep sufficiently, so that the roots have enough depth to set up and endure the winters. For bigger cacti, at least 2 feet of depth is recommended and avoid planting them too close to each other. Give the roots sufficient space to grow over the winter water table.
