If you have ever been to a desert, you’ve probably wondered how cacti survived the diverse environmental condition. They must have powerful roots that sustained them through drought, strong winds, and periodic downpours. What do their roots look like from beneath the surface?
Cactus roots look woody and extensive. Their roots evolved to gather water more efficiently and quickly than other common plants to sustain their life in the desert. Cacti roots adaptations include 1) deeper taproots, 2) shallow fibrous roots, 3) tuberous roots, and 4) aerial roots.
Cacti rely on their roots to survive since they are responsible for the plant’s large portions of water uptake. But what makes cacti roots so efficient in supplying water for the whole plant? Let’s start by understanding the root systems of cacti.
Cactus roots have a woody look and texture that can suck in water and store it. The four most common types of cacti roots are :
- Deep taproots,
- Shallow fibrous roots,
- Tuberous roots, and
- Aerial roots.
A cactus’s root system is often shallow or deep connected by the clustered fine roots. They hold a significant role in cacti survival because they provide a substantial amount of water and nutrients for the plant. Aside from storing water on their stems, some cacti species retain water on their roots.
To effectively do this, cactus roots developed impressive adaptations to sustain life even in extreme drought. Each species have a particular root type that corresponds to the size and shape of the cactus stem.
Cacti taproots are long and chunky. They stretch downwards and get deep into the ground. It is the first type of root to develop upon germination; thus, it is the primary root and the largest among other roots. Deep taproots can access water sources in deeper subsurfaces and anchor the plant.
Some cacti have multiple taproots for more efficient water absorption. Taproots do not only absorb more moisture but also hold the plant in the ground. It can also help minimize moisture loss because it is deep, storing the water away from dry air and desert heat above the ground.
Cacti that grow big and tall such as Pachycereus, are likely to develop deeper taproots for strong anchor during strong desert winds. Species growing in a region that receives more rain have roots that extend deeper to reach as much water and nutrients as possible.
Some species produce longer taproots that measure more than the length of their stem and several secondary fibrous roots. As the cactus matures, its taproots will become thick and woody. When growing cacti with extensive taproots, a deep, wide container is ideal for their optimum growth.
Another type of cacti roots are shallow fibrous roots. Most cacti species grow them from the taproot. These roots tend to be shallow and do not penetrate deep below the surface but spread and branch several feet away from the base of the plant. This characteristic allows the cacti to absorb water easily during a downpour.
The shallow roots are adapted to collect any moisture available in the soil, so spreading to more ground ensures more hydration. When rain falls, the roots close to the surface get access to the water quickly and thoroughly absorb as much water and nutrients for the plants.
Thirsty roots begin to rehydrate and branch new strands to collect every drop of moisture. Fibrous roots are as important as the taproots, but they are short-lived. Cacti species that do not produce extensive taproot rely on their numerous fibrous roots for resources.
The shallow fibrous roots are common among barrel or round shape cacti. Cultivating these kinds of species requires wide pots to hold their spreading roots. Some cacti with extensive shallow roots are Gymnocalycium, Melocactus, and Golden Barrel Cactus.
Tuberous roots are another type of cactus root system. These cacti roots look like tubers and grow vertically, branching a few tiny secondary roots. They are not particularly deep like the taproot. These roots store water and food for long periods. Tuberous roots are quite thick like
Cacti in regions with rare precipitation develop tuberous roots. They have adapted large swollen roots to store adequate water and food in preparation for drought. They can survive long months without water than those that don’t have. Lophophora and Pediocactus are some cacti with thick roots.
Aerial cacti roots are white or pink thin roots growing on the sides of the cactus stem. When the primary cactus roots do not get enough water from its soil, but humidity in the surrounding is high, aerial roots will begin to grow and collect moisture from the atmosphere to provide for the plant.
Aside from absorbing moisture from the surrounding, cacti use aerial roots to anchor their stem to cling on surfaces as they grow. They are common on cactus with long thin stems, such as the epiphytic Schlumbergera species, Rhipsalis, Hylocereus, and Epiphyllum.
Growing root hairs is an interesting adaptation of cacti roots to harness valuable water. These roots are white hair-like strands that proliferate from the existing roots when moisture is available.
When the substrate is saturated during rainfall and the roots enjoy a good drink, the cactus will shoot up new fine roots. The root hairs aim to increase the soil surface area covered by the root system and ensure adequate water collection. As the soil becomes dry again, the roots hairs begin to shed and die away.
They have a limited lifespan as they are too thin and dehydrate easily. The shedding and dying of root hairs prevent moisture from being absorbed back by the soil and eliminate the need for the cactus to use its energy to maintain them. New root hairs will grow when water becomes available again.
Do broken cactus roots regrow?
Although broken roots will not regrow, the root tip will give off new strands of healthy roots that will efficiently provide water and food for the plant.
A cactus can go on for weeks or a few months without roots, but it cannot live without roots. It will shrink and suffer from dehydration and eventually die away. However, a cactus without roots will normally grow new roots, with moon cactus as an exception.
Root trimming does not keep your cactus small or stunt its growth. Its vigour may decline for 3 to 4 weeks after pruning while it regenerates new root growth. However, after this brief period, your cactus will become more lively as new roots emerge.
Although pruning sounds scary, it does not have harmful effects if done correctly. However, trimming your cactus roots repeatedly can make its root ball dense. Every trimmed root strand will spur new roots making your plant’s root system thicker and denser.
While it is good news for your plant to have an extensive root system for water absorption, it will require more volume of soil mix and a bigger container.
Cactus roots below the surface will be disturbed by mealybugs and scale insects that feed on the sap of the roots. For cactus roots that protrude above the surface, grazing herbivores such as camels and javelinas in the desert can eat them if they have access to it.
- Cactus have adapted different root systems to collect as much water as possible and survive the harsh desert condition. Cactus roots have two or more of these roots; deep taproots, shallow fibrous roots, tuberous roots, and aerial roots.
- Root hairs are essential in cactus during rainfall because it helps gather more water. However, they die away when water is not accessible anymore.
- Pruning cactus roots will stimulate new root sprouts and strengthen the cactus root systems.
- “Cacti: ROOT STRUCTURE AND FUNCTION,” by Joseph G. Dubrovsky and Gretchen B. North, University Of California
- “Pricklypear Biology and Management,” by Charles R. Hart and Robert K. Lyons, Texas A & M University
- “Root Succulence In Cacti,” University Of Texas
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