The “seaweed cactus,” scientifically known as Epiphyllum guatemalense, is a distinctive and appealing houseplant. Its common name comes from its unique, wavy, and crinkled stems that cascade, creating a visual resemblance to seaweed. This plant is classified as an epiphytic cactus, naturally growing on other plants like trees in tropical environments, which significantly influences its care requirements compared to traditional desert cacti.
Seaweed Cactus Care
Cultivating a healthy seaweed cactus involves understanding its specific needs, which differ from those of arid-loving cacti.
The seaweed cactus thrives in bright, indirect light, mimicking its natural habitat where it receives filtered sunlight through a tree canopy. Exposure to direct, harsh midday sun can scorch its delicate stems, leading to yellowing or browning. An east-facing window is often suitable, or a south or west-facing window where the plant is set back a few feet to avoid intense afternoon sun.
Water thoroughly when the top layer of soil feels dry to the touch, ensuring excess water drains away from the pot. While it appreciates consistent moisture, prolonged soggy conditions can lead to root rot; therefore, allowing the top third of the soil to dry between waterings is beneficial. This plant also prefers higher humidity levels, ideally above 50%, which can be achieved by placing the pot on a pebble tray filled with water or by using a humidifier.
A well-draining, airy soil mix is essential for the seaweed cactus. An orchid mix or a succulent mix amended with perlite, pumice, or bark chips provides the necessary drainage and aeration. For optimal growth, repotting is typically needed every two to three years, or when roots begin to emerge from the drainage holes.
Seaweed cacti prefer warm temperatures, with an ideal range between 18°C and 24°C (65°F and 75°F). They are sensitive to cold and frost, so temperatures should not drop below 10°C (50°F). Protecting them from cold drafts is also important for their well-being.
During the active growing season, from spring through summer, a balanced, diluted liquid fertilizer (such as a 10-10-10 ratio) can be applied every four to six weeks. Epiphytic cacti naturally grow in low-nutrient environments, so feeding sparingly is recommended to avoid burning the roots. During fall and winter, fertilizer application should be reduced or stopped as the plant enters a period of slower growth.
Encouraging Blooms
Prompting a seaweed cactus to bloom involves specific environmental cues and a degree of plant maturity. Mature plants are more likely to produce flowers, which typically appear from early spring to late summer.
Bright, indirect light is important for flower production. A cooler, drier rest period during late fall and winter can stimulate bud formation. Maintaining temperatures between 11°C and 14°C (52°F and 57°F) during this time encourages flowering.
Watering should be reduced during the cooler, drier rest period, allowing the soil to dry out more between waterings. Once flower buds appear, the plant can be returned to its usual warmer position, at or above 15°C (60°F). Some growers also find that a low-nitrogen fertilizer (such as a 2-10-10 ratio) applied in late winter can help promote blooming.
Propagating Seaweed Cactus
Propagating seaweed cactus from stem cuttings is a straightforward and effective method to create new plants. This process allows gardeners to expand their collection or share with others.
To begin, select a healthy stem segment at least 10 cm (4 inches) long and make a clean cut using a sharp, sterile knife. After taking the cutting, allow the cut end to “callus over” for several days, or even up to a week, until a dry, protective scab forms. This callusing prevents rot when the cutting is planted.
Once the cutting has callused, plant it about 2.5 to 5 cm (1 to 2 inches) deep in a well-draining potting mix, such as an orchid or succulent mix. Initially, water sparingly until roots begin to form, typically within two to six weeks. Providing warmth and indirect light during this rooting phase supports successful establishment.
Common Problems
Even with proper care, seaweed cacti can encounter certain issues. Recognizing the signs of distress helps in addressing problems promptly to maintain plant health.
Yellowing or drooping stems often indicate watering issues. Yellowing can point to overwatering and potential root rot, especially if the stems feel soft and mushy. Conversely, drooping or shriveling stems, which may also appear wrinkled, can suggest underwatering or insufficient humidity.
A lack of growth or stunted growth may stem from insufficient light, inadequate nutrients, or incorrect watering practices.
Common houseplant pests such as mealybugs or scale can affect seaweed cacti. Inspecting the plant regularly helps detect infestations early, and organic treatment methods, such as neem oil or insecticidal soap, can be used to manage them.
If the plant fails to bloom, it might be due to immaturity, as younger plants are less likely to flower.
Browning or crispy stems are typically a sign of too much direct sun exposure or insufficient humidity.