The Hoya carnosa ‘Rubra’, known as Krimson Princess, Krimson Queen, or Tricolor Hoya, is a popular houseplant. Its succulent-like leaves feature green, white, and pink variegation, which intensifies to a vibrant blush in good light. This vining plant produces clusters of fragrant, star-shaped flowers. The ‘Rubra’ cultivar is a favored choice for indoor growers due to its beauty and straightforward care.
Core Care Requirements
Light
The Rubra Wax Plant thrives in bright, indirect sunlight. An east or north-facing window is ideal, as direct, intense sunlight can scorch its variegated leaves. While it tolerates slightly lower light, this reduces variegation vibrancy and inhibits flowering. Bright, indirect light encourages pink hues in new growth and promotes blooms.
Watering
Hoya carnosa ‘Rubra’ is semi-succulent, storing water in its thick, waxy leaves. It prefers its soil to dry out between waterings. Water thoroughly until water drains from the pot’s bottom, then allow the top few inches of soil to dry completely. Overwatering causes root rot, a common issue, while prolonged underwatering can cause leaves to wrinkle or become limp.
Soil and Potting
A well-draining, airy potting mix is essential for the Rubra Wax Plant. A suitable blend includes regular potting soil mixed with amendments like perlite, orchid bark, or pumice. This prevents waterlogging, which is detrimental to the plant’s roots. Hoya plants prefer to be somewhat root-bound, which can encourage flowering.
Temperature and Humidity
The Rubra Wax Plant prefers warm temperatures, between 60°F and 85°F (16°C and 30°C). It tolerates average household humidity, but moderate to high humidity (around 50-60%) promotes healthier growth and flowering. To increase humidity, group it with other plants, use a pebble tray, or run a small humidifier nearby.
Fertilizing
During its active growing season in spring and summer, the Rubra Wax Plant benefits from regular fertilization. A balanced, water-soluble liquid fertilizer, diluted to half strength, applied every 2 to 4 weeks, is sufficient. Over-fertilizing can harm the roots. Reduce or cease fertilization entirely during the cooler, dormant winter months.
Growth and Maintenance
Pruning
Pruning the Rubra Wax Plant can maintain its shape, manage size, or encourage bushier growth. Avoid removing peduncles, the small spurs from which flowers emerge, as the plant re-blooms from these spots in subsequent seasons. Trimming also helps remove leggy or damaged stems.
Repotting
Hoya carnosa ‘Rubra’ prefers to be somewhat root-bound. Repotting is needed only when the plant is severely root-bound, every two to three years, or when the potting mix appears depleted. Select a pot one or two inches larger in diameter than the current one to prevent overwatering. The best time for repotting is during the plant’s active growing season, spring or early summer.
Propagation
Propagating the Rubra Wax Plant is achieved through stem cuttings. Take a healthy stem cutting with a few leaves, making a clean cut below a node. Root the cutting in water or directly in a moist, well-draining potting mix. Provide bright, indirect light and maintain consistent moisture to encourage root development over several weeks.
Addressing Common Problems
Pests and Diseases
The Rubra Wax Plant can encounter common houseplant pests such as mealybugs, spider mites, aphids, and scale insects. These sap-sucking pests weaken the plant, causing distorted growth or yellowing leaves. Inspect the plant regularly for early detection. Infestations can be managed by wiping pests away, spraying with a strong jet of water, or applying insecticidal soap or neem oil solutions. Root rot, a fungal disease, is caused by overwatering and poor drainage, leading to wilting, yellowing leaves, and mushy stems.
Leaf Issues
Yellowing leaves can indicate overwatering (soft, mushy leaves) or underwatering (dry, crispy leaves). Nutrient deficiencies also cause overall yellowing, often starting with lower leaves. Brown or crispy leaf edges point to underwatering, low humidity, or too much direct sunlight. Leaf drop results from stressors like watering issues (over or under), temperature shock, or insufficient light. Identify the underlying cause to resolve these leaf problems.