How Deep Do Cactus Roots Grow?

If there is one plant that has enough endurance and tolerance to cheat death, it is none other than a cactus. With lifespans longer than a century, cacti in the USA have the natural adaptation to thrive in unideal living conditions for shockingly long periods.

While a cactus’ remarkable resilience can be attributed to its thorny exterior and thick water-storing trunk, the roots play a huge part in ensuring that the desert plant stands tall against all odds.

Different cactus species generally have different kinds of roots that grow to varying depths. It all comes down to how easy it is for the desert plant to find moisture in its soil.

Keep reading to learn in detail how cactus roots behave differently from other roots, the four types of cactus roots, and how deep they can go.

How Do Cactus Roots Behave Differently than Other Plant Roots?

The desert cactus is one the toughest plant species in the entire plant kingdom. These plants hold hydration flawlessly through extended periods of drought-like conditions and can also grow to tremendous heights without the availability of excessive nutrients, water, or minerals.

Had the cactus roots behaved exactly like other plant roots, the desert plant would have been almost impossible to last as long as it did.

However, what exactly do the cactus roots do?

Before we discuss the unique characteristics of the cactus root system, let us highlight the basic similarities.

The Similarities

  • Like all other plant roots, the cactus roots also divide into many branches that spread out in search of hydration.
  • Moreover, cactus roots also facilitate the absorption of micronutrients and minerals, which help accelerate the plant’s growth and boost its immunity.

The Differences

Absorption Capacity

What makes the cactus roots unique is their ability to absorb any amount of moisture they may find and their distinct quality to hold and store water within their tubular structures.

In general, all plant roots have a limited capacity to absorb moisture. No matter how much water you provide, their roots will only absorb the amount their cell capacity permits.

Cactus roots have the special ability to absorb, store, and push any amount of water they can find. Since these roots are adapted to living in dry soil, this quality allows them to soak up as much moisture as possible for conservation.

However, although such unique root systems help keep the cactus plant hydrated through prolonged and severe droughts, they can pose a problem when too much water is available.

For instance, if you overwater a potted cactus, its roots will absorb all of the available moisture, which can eventually lead to root and stem rot.

Unique Outer Layer

Another unique feature of the cactus root is its thick and waxy outer layer. Although the cactus can absorb all available water, its dry and arid living conditions usually make water conservation quite challenging.

Hence, the desert plant has a cork-like layer covering all its roots. This layer helps facilitate the movement of water inside the roots; however, it prevents any absorbed water from leaking into the soil. As a result, the cactus has a better chance of conserving the moisture it can find.

How Deep Do the Four Types of Cacti Roots Go?

As mentioned earlier in this article, different types of cactus roots will spread around to different depths. Usually, the exact depth varies according to the cacti species and its unique needs.

For instance, if you have a small potted cactus plant that you water at least once every two to three weeks, the cactus roots will not need to grow too deep.

Instead, since water is easily available, the roots will only grow a few inches deep and usually remain close to the surface. This is exactly why indoor cacti are grown in small and shallow pots.

Cactus root types are generally divided into four categories that vary in terms of their structures and depths.

To learn more about these types, pay attention to the list below.

1. Taproot

Generally, the tall and large cactus species that grow in dry and arid soils have taproots. The taproot is usually just a single long root that grows deep into the soil in search of water.

Apart from finding moisture, these roots help anchor the tall cactus species and allow them the stability they need to grow vertically upward.

Moreover, while the taproot does most of the work, other, shallower roots grow around the top of the taproot. These roots help collect water from the soil’s surface and generally spread sideways into the soil.

One of the best examples of cacti species that have taproots is the Saguaros cactus.

The Saguaros cactus is usually always found in the wild and can grow to a whopping 40 to 60 feet in height. Since this monstrous cactus needs more water to store and use, its taproot will extend nearly 2 feet deep into the ground in search of water.

Moreover, such deep roots also help anchor the massive Saguaros cactus’ 3200 to 4800 Lb (about 2177.24 kg) weight and allow it the structural foundation it needs to stand tall and grow up.

2. Napiform Roots

Napiform roots are generally common in the smaller cactus species. These turnip-shaped roots have wide, thick, and short bodies that narrow towards the bottom, where many smaller and thinner roots grow.

Since the smaller cactus species do not have long, vertical bodies to conserve water, they are able to store water, nutrients, and minerals in these thick roots.

Although the napiform roots do not grow super long, cacti with such roots generally thrive in deeper pots where water is not abundant.

3. Fibrous Roots

The most common type of roots found in most cacti species are the fibrous roots. These roots have numerous branches and can be up to fifteen feet long.

Moreover, such fibrous roots generally spread sideways into the Earth and remain close to the surface. This helps them collect water quickly whenever it rains.

Furthermore, fibrous roots branch out aggressively into new lateral roots during the rainy season and wrinkle up when rainwater is scarce.

If the dry spell gets too long, the cactus will lose most of its lateral roots to conserve water and nutrients. 

4. Tuberous Roots

Finally, the last type of cacti root is the tuberous root. These roots grow vertically downwards, branch a lot, and are generally thick to store as much moisture and nutrients as possible.

Moreover, smaller and thinner roots grow around the thick tuberous roots to further increase water absorption and reach deeper into the soil.

In general, cacti with tuberous roots are grown in deep pots and are watered at least once every two weeks. 

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Final Thoughts – Keep a Cactus as a Houseplant!

Since water is scarce in the desert soil, most wild cactus’ roots will spread out to nearly fifteen feet away from the parent plant in search of moisture. However, the exact depth of a cactus’ roots will depend on the parent plant’s species and its living conditions. The lesser the availability of water in the soil, the deeper the cactus plant’s roots will be.

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