Cacti and succulents are popular choices for plant enthusiasts due to their striking appearance and hardiness. Despite their resilience, owners are often concerned by the sudden appearance of unexpected lumps, bumps, or discolorations on the plant’s surface. These growths can be alarming, suggesting a potential health issue that requires attention. Understanding the characteristics of these abnormalities is the first step toward effective treatment. This article guides you through diagnosing the various causes of these textural changes and provides actionable steps for remediation and future care.
Visual Diagnosis of Cactus Bumps
A thorough visual inspection is the initial stage in determining the source of abnormal growth on your cactus. Begin by assessing the bump’s texture, which indicates its origin. Soft, slightly squishy growths suggest an internal issue related to water pressure. Conversely, hard, woody, or rough spots often indicate a cellular change or external infestation.
The location of the abnormality also provides significant diagnostic clues. Hard, brown, or cork-like patches that originate at the base and move upward are typically signs of natural aging or environmental stress. Fuzzy or cottony masses clustered in crevices or along the plant’s apex are strong evidence of a pest infestation. Pay close attention to the color, noting if the bump is the same green as the stem, or if it is a distinct yellow, black, or reddish-brown spot.
Environmental Stressors Leading to Lumps
Many textural changes on cacti stem from improper cultivation practices rather than living organisms. One common non-biological condition is edema, which manifests when the plant takes up water faster than it can transpire it through its stomata. This rapid influx of water creates internal pressure, causing epidermal cells to burst and collapse. The resulting damage appears as raised, corky, or rust-colored spots, often signaling inconsistent watering cycles or high ambient humidity.
Another frequent cause of hardening or lumpy texture is corking, a natural physiological process analogous to scar tissue formation. This change involves the lignification of the cactus’s lower cells, giving the tissue a dry, woody appearance. Corking usually begins near the soil line and progresses slowly up the stem, acting as a protective barrier against physical damage and moisture loss. While irreversible, this hardened tissue is not a disease and does not spread aggressively. Corking is usually symmetrical and uniform, unlike pest damage.
Pests and Pathogens Causing Bumps
When bumps are biological, they are often caused by parasitic insects that feed on the cactus’s internal fluids. Scale insects are notorious for creating small, dome-shaped, waxy bumps that are difficult to scrape off. These insects anchor themselves and form a hard, protective shell over their bodies. Their feeding extracts sap, leading to localized yellowing and the death of the surrounding tissue.
Another prevalent pest is the mealybug, which secretes a white, cottony wax that protects the colony. These soft-bodied pests often congregate in sheltered, tight spaces, such as areoles and growing tips. The cottony mass is a combination of the insect and its protective waxy ovisac, giving the plant a fuzzy, lumpy appearance. Fungal pathogens can also cause raised lesions, appearing as distinct, discolored spots (yellow, black, or red) that indicate localized tissue decay as the plant attempts to wall off the infection.
Remediation and Long-Term Care
Addressing environmental issues like edema requires immediate modification of the plant’s moisture management. For a cactus showing signs of burst cells, allow the soil to dry completely before the next watering, then significantly reduce irrigation frequency. Improving soil drainage by adding grit or perlite and ensuring better air circulation helps the tissue heal and prevents future cellular rupture. While corking cannot be reversed, its progression can be slowed by maintaining consistent, appropriate watering and avoiding sudden environmental shifts.
Treating pest-related bumps necessitates physically removing the parasitic organisms. Small scale infestations can be managed by gently scraping the individual shells off the surface using a soft toothbrush or cotton swab dipped in isopropyl alcohol. For mealybugs, dab the cottony masses directly with a cotton swab soaked in 70% isopropyl alcohol, which dissolves their protective waxy coating. Horticultural oils or insecticidal soaps can be applied as a broader treatment, but always test a small area first to prevent phytotoxicity.
When dealing with fungal lesions, the affected tissue must be surgically removed to prevent the spread of spores. Use a sterile, sharp blade to cut out the discolored area, ensuring removal of a small margin of healthy tissue around the bump. After pruning, allow the wound to callous over in a dry environment, and sterilize the cutting tool with a bleach solution to avoid contaminating other plants. Long-term care involves providing bright light, maintaining appropriate temperatures, and routinely inspecting the plant.