The desert is an inhospitable habitat for most plants – but not for cacti. With its elevated temperatures and prolonged drought season, you may wonder how cacti can survive such harsh environments. And, since the desert is dry almost all of the time, you might also start to question whether these succulents even have roots.
Cacti are drought-resilient, which means they can survive without water for months on end. That does not mean, however, that they do not have roots. Like any other plants, they rely heavily on their roots for survival.
The only difference between cacti and most normal plants is the nature of their root system. Cactus roots have their own unique capabilities that allow them to thrive even during prolonged dry spells. These roots are known for their impressive adaptations that aid the plant’s survival in extremely dry areas, as they have evolved to efficiently collect as much moisture as possible from the soil and the surrounding air.
There are various types and shapes of cactus roots; if you are curious about what they look like underneath the soil, read on to learn more!
What do cactus roots look like?
Different species of cacti can have different types of roots. Some have long, thin, hair-like roots that grow closer to the soil’s surface, while others have thick, long roots that grow further into the ground.
The thin root strands are more common during the rainy seasons, because these fibrous roots can easily collect rain water from the surface of the soil. However, these roots are short-lived and wither during the dry season.
On the other hand, thicker and longer roots can penetrate deep into the soil’s sublayers to collect as much moisture as possible. Most cacti have these roots as the primary backbone of their root system, but there are some that rely solely on their fibrous roots to survive.
Cactus roots fall into four different types – aerial roots, tap roots, lateral roots, and tuberous roots. Each type has its own unique features and purpose, described in more detail below.
Types of cactus roots
Cacti can have one or a combination of several types of roots, each having their own purpose to aid survival in areas with limited water supply. These roots are:
1. Aerial roots
Aerial roots, or air roots, are the ones that grow along the plant’s stem. Not all succulents will have aerial roots; it is more common among species with stems, such as Sedums, Echeverias, and Christmas cacti. Moreover, these pink or white strands only grow when the succulent needs your attention.
First, your cactus may not be getting enough water from the soil, and if it is kept in a humid environment, it will start to collect water from the surrounding air instead. And, since succulents can only absorb water through roots, it will start growing these air roots in an effort to capture moisture and hydrate itself.
Second, succulents may send off aerial roots if they are stretching out to get enough sunlight. These desert plants thrive in areas with a lot of light, so if you keep your plant in low-light conditions, it will actively grow in search of a better light source. Having said that, it is also not advisable to place the plant under direct sunlight all day, as this might cause sun damage to the foliage.
Although air roots can be unsightly, they usually are not a cause for serious concern. You may trim them off for aesthetic purposes, but you should consider this growth as a warning sign that your succulent is not getting the right amount of water or sunlight.
2. Tap roots
Tap roots are the plant’s primary and largest roots, formed for efficient water absorption. These long, thick roots are the first type of root that the plant develops right after germination.
Tap roots grow downwards to reach the nutrients and moisture deep in the soil’s subsurface layers. Since the roots extend far into the soil, the cactus can easily access and store enough water to survive the extreme desert heat above-ground.
Aside from absorbing water and nutrients, tap roots are also used to support the cactus in the ground. Since the roots are so thick and deeply lodged in the soil, they become the succulent’s anchor and help keep it upright in the strong desert winds.
Over time, the tap roots will start to sprout lateral roots as it continues to grow longer and thicker. These roots serve as the succulent’s backbone and lasts throughout its life.
3. Lateral roots
The lateral roots are those that branch off from the tap roots, growing outward in all directions to capture more water quickly and efficiently. In fact, the majority of the cactus’ roots are lateral roots.
Lateral roots, also known as adventitious roots, play an important role in the succulent’s survival in the hot desert. Unlike the primary root, these widespread, thin, hair-like roots do not grow deep into the soil; they grow close to the surface to harvest rainwater and nutrients.
When a rain shower occurs, the lateral roots can quickly absorb the rainwater from the soil’s surface. At this time, new lateral roots will develop to help the plant collect every last drop of water to be stored and keep the plant hydrated. Hence, lateral roots do not need to be thick and long to penetrate deep down into the soil. The more area they can cover, the more water they can collect.
During the hot season, some of these lateral roots will wither away. Although they are short-lived, they can quickly branch out anew when the rainy season starts again. Some cactus species that have spreading lateral roots include the Melocactus, Gymnocalycium, and the golden barrel cactus.
4. Tuberous roots
Tuberous roots are common in succulents that grow in areas with rare precipitation. These thick, absorbent roots collect and store all the nutrients and moisture they can find in preparation for the drought season. Cacti with tuberous roots are extremely resilient desert plants, and can survive even months without any rainfall.
Some common cacti with tuberous roots are the Pediocactus and Lophophora.
Cactus root hairs
Cactus roots are highly adaptable to their environment and the available water sources.
When the soil starts to become wet with rain water, their existing roots start to rehydrate and form new, hair-like roots. These new roots spread widely to cover a greater surface area and ensure an adequate amount of water is collected.
Since these cactus root hairs are very thin, they can easily dehydrate and wither, so when the dry season returns, they simply fall off. Surprisingly, this is not a loss for the plant; on the contrary, the death of its thin roots serves another important purpose for its survival. The withering of the roots prevents any moisture from being absorbed back into the soil, allowing the cactus to preserve more water during extreme drought.
Most of the cactus root hairs will only grow back once the rainy season starts again.
How deep can cactus roots grow?
The cactus’ root system is uniquely adapted to harness valuable water and survive the harsh climatic conditions of the desert. Depending on their type and purpose, cactus roots can be very thick and long to absorb moisture from deep within the soil, or they can be very thin and hair-like, allowing for quick collection of water during a rain shower.
Cactus roots can extend up to three or four feet into the ground, while growing up to three feet horizontally. This is the plant’s technique – to disperse its roots as deep and as wide as it can to collect an adequate amount of water and survive the prolonged drought season.
Can a cactus survive without roots?
Just like any other plant, cacti cannot live without their roots. These are a plant’s lifeline: through its roots, the cactus absorbs the nutrients and water that it needs to live. Without its roots, it will start to wither and die.
Since cacti are highly drought-resilient plants, they can survive temporarily – for a couple of weeks or months – without roots. With the exception of the moon cactus, most cacti without roots will eventually start growing new roots. High humidity and a sufficient water supply can help speed up the growth of these new roots.
The bottom line
Cacti do indeed have roots: they are the plants’ lifeline for survival in harsh environments like the desert. These plants’ powerful root systems are uniquely adapted to live in areas with limited water resources. Some cactus roots grow deep into the ground, while others grow shallow and laterally near the surface.
Although cactus roots come in various shapes, thicknesses, and lengths, they all share the same purpose: to harvest enough nutrients and moisture from their environment to keep the plant alive in the harsh desert.
Image: istockphoto.com / maaram