Are Cacti Hollow? If So Get Worried


You noticed your cactus dropping and soft to touch. When you examine it, the stem seems to be recessed from the inside, and it makes you think that cacti have hollow stems. Is this the case?

Living cactus stems are not hollow. On the contrary, they are made up of soft packets of tissues filled with moisture. However, if a cactus is dead for a long time, it will eventually become hollow due to the decomposition of its inner soft tissues. In general, a hollow cactus cannot be recovered as it is already decomposing.

The cactus stem is a special part of the plant due to its ability to store a significant amount of water to resist drought. Read more and learn what makes up the inside part of a cactus plant.

Are Cacti Hollow – Infographics

What Is Inside A Cactus?

Cactus stems are made up of specialized cell tissues that can hold water to keep the plant hydrated even without being watered. Unlike other plants, cactus stems are photosynthetic. The stem’s interior comprises different parts such as vascular tissues, parenchyma cells, chlorenchyma cells, and mucilage cells.

This is a cross-section of the stem of Parodia Warasii.

The cacti’s ability to endure periodic drought is due to its stellar stems that function effectively by stashing water in its collapsible tissues. The inside of the cactus has soft tissues filled with water and nutrients needed for hydration and photosynthesis.

So, what inner parts of the cactus can do such a great job in storing water? Well, there is not only one part but rather 4!

1) The Vascular Tissues

Vascular tissue bundles are cylindrically internal vessels in the stem and connected to the roots. It contains the xylem and phloem responsible for transporting water and nutrients throughout the cactus system.

As the cactus ages, the vascular tissues develop a woody structure inside the stem called vascular cambium. The formation of the vascular cambium is necessary to support the cactus as it gets bigger. The vascular cambium has layers of xylem tissues that effectively transport water and nutrients from the roots up to the entire stem.

Phloem tissues are another strand of tissues that work hand in hand with the xylem by carrying organic substances such as sugar from the site of photosynthesis throughout the cactus body.

2) The Parenchyma Cells

Parenchyma cells are the inner region and collapsible part of the cactus stem. They are the main water reservoir of the cactus. There are several types of smaller parenchyma cells in plants, but the chlorenchyma and mucilage cells are the most common ones among cacti.

When cacti roots contact moisture, their natural response is to absorb it and store it in its water-storage cells called parenchyma cells. The cells have thin, smooth, and flexible walls, usually light green and soft because it contains mostly water.

Water-filled cells appear to be smooth and bloated, while the slightly dehydrated cells have collapsed cell walls. On the other hand, the extremely dried cells are flaccid and shriveled.

As more water is absorbed, the sponge-like parenchyma cells become turgid, swelling with water. During drought, when the quantity of water within the plant diminishes, the parenchyma cells release water to other cells. Consequently, as the parenchyma gives up water, it shrinks.

The transfer of water to other neighboring cells minimizes water stress and allows photosynthesis to go on. On prolonged dry spells, the parenchyma cells will become empty and collapse over time.

3) The Mucilage Cells

While the inner parenchyma cells absorb water, the mucilage cells firmly retain water preventing it from evaporating. The cell has a slimy and sticky substance made of carbohydrates that bind to water.

Although mucilage cells have thin walls, they are compact enough to inhibit water loss. It helped the cacti to preserve water in preparation for drought. Like the inner water-holding cells, mucilage cells also provide water to the rest of the cells when water intake is scarce. Mucilage cells are often visible on Opuntia and Uebelmannia species.

4) The Chlorenchyma Cells

Chlorenchyma cells are the type of parenchyma cells that have chloroplast. This makes them responsible for manufacturing and storing foods for the future consumption of the cactus through photosynthesis.

The chlorenchyma cells.

The green coloring in the stem just underneath the epidermis of certain cacti plants is due to chlorenchyma cells. It comprises the part of the stem where photosynthesis takes place. Chlorenchyma is the outer layer and is not as flexible as the inner parenchyma. The cell walls are thicker and more rigid.

Does Cactus Have A Hollow Stem?

A living cactus does not have hollow stems. Its internal tissues are moist and filled with water. However, if the cactus is dead for a while, it will become hollow as the soft tissues in the stem decompose.

Are Dehydrated Cactus Hollow?

The cactus will become hollow if it is severely dehydrated. The once water-filled parenchyma tissues will dry up and recede over time, leaving only the woody vascular cambium inside and the thick epidermis outside.

Naturally, all cacti stems are compact. The inside of the stems is packed with very functional tissues that keep the plant alive and vigorous. Given the appropriate growing requirements, the cacti stem will remain intact and sturdy. Water supply is an essential factor that keeps the cacti stem plump and green.

While cacti are very tolerant to the dry season, they still need water to rehydrate their thirsty and empty stem tissues. If a dehydrated cactus remains unwatered for a prolonged period, chances are, water-holding tissues will collapse.

A severely dehydrated cactus with parched epidermis and hollow interior

Will a dehydrated cactus survive?

A cactus deprived of water will show early signs of wilting and shrinking. In such a case, inspect your cactus immediately. If the potting mix is dehydrated, then your cactus badly needs a quencher. Water your cactus twice a week until it regains its energy. After that, you can water once a week or when the medium is approaching dryness.

However, a severely dried-out cactus that is hollow from the inside is impossible to save. A heavily withered cactus has dead stem tissues that cannot be redeemed.

What Causes a Hollow Cacti? Too Much Water, Fungi, and Pests

One of the main reasons for a cactus to become hollow is the excess watering that will cause the plant cells to burst and die. This will make the stem mushy, soft. This is the beginning of the decomposition process and the end of the plant.

Needless to say that such a stem will no longer be able to absorb the essential nutrients needed to perform photosynthesis. The cactus will start to weaken and become more prone to health issues such as stem rot which causes the cactus’ interior to begin decaying.

Fungal infections can cause the cactus to rot and turn hollow.

Another possible cause of cactus decay is due to fungal or bacterial infection and pest infestation. Fungus and bacteria are often the common cause of a rotting cactus. When the cactus is infected, it will start decaying quickly. What’s worse is that it will rapidly spread with other neighboring cacti.

Pests such as scales, aphids, and mealybugs are fed on the sap of the cactus. These pests reproduce in a mass that covers the stem of the cactus. Imagine hundreds of tiny insects sucking the juice out of the cactus stem. The plant cannot survive this attack and will succumb to rot if the pests are not eliminated.

You can prevent your cactus from rotting and turning hollow by closely inspecting your plants to detect early signs of rotting and dehydration. In that way, you can take quick actions to curb the issue before it gets worse.

Takeaways

  • Cacti do not have hollow stems. Instead, it has closely packed stem tissues filled with water and nutrients that the plant needs.
  • Hollow cactus are those that are dehydrated and rotten. Decayed cactus have hollow stems that are not savable.
  • Cacti stems are composed of several layers, but the most functional features are the vascular tissues, parenchyma, chlorenchyma, and mucilage cells.

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Esther

Esther is the self-proclaimed cactusholic :D of the team. She owns a cacti shop with hundreds of plants that she takes care of. Esther has many years of experience in growing and caring for drought-resistant plants like cacti and succulents.

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