The Hoya carnosa ‘Tricolor’, also known by the cultivar name ‘Krimson Queen’, is prized by enthusiasts for its unique waxy foliage. This specific variety features leaves with creamy white or yellow variegation along the margins, but its true appeal lies in the potential for stunning pink and ruby-red coloration. Achieving this vibrant pink hue is a matter of intentionally manipulating the plant’s environment to trigger a natural protective response. This guide details the precise care adjustments necessary to encourage and sustain the desired vibrant coloration in your Hoya’s new growth.
Why Hoya Leaves Turn Pink
The striking pink or red color that appears on the new leaves is not the plant’s natural, permanent pigment but rather a stress response. This coloration is due to the plant producing anthocyanins, which are water-soluble pigments responsible for red, purple, and blue hues. Anthocyanins serve as a natural sunscreen, protecting the delicate, chlorophyll-deficient white parts of the new foliage from light damage.
When exposed to higher light levels, the Hoya synthesizes these protective pigments. The pink color is often most intense on the newest leaves and tends to fade to white or cream as the leaf fully matures. The presence of this color is a visual indicator that the plant is receiving sufficient light stress to activate this defense mechanism.
Essential Light Requirements for Color
Light intensity is the single most important factor for inducing pink coloration, as it directly stimulates anthocyanin production. While the Hoya ‘Tricolor’ thrives in bright, indirect light for general health and growth, a higher intensity of light is required to trigger the desired color change. The goal is to provide light that is high in intensity without causing actual scorching or damage to the foliage.
Placing the Hoya in an east-facing window offers bright morning sun, which is strong enough to encourage color without the harsh heat of midday light. South or west-facing windows can also be effective, but the midday and afternoon sun must be filtered through a sheer curtain or by positioning the plant a few feet back from the glass. This filtering prevents sun scorch, which appears as brown, necrotic spots.
If natural light is insufficient, full-spectrum LED grow lights are an excellent alternative for precise control. Position a grow light approximately 12 to 18 inches above the foliage for a duration of 12 hours a day to mimic the necessary high-intensity light environment.
Influencing Color Through Care Practices
Beyond light, specific care adjustments create the mild, controlled environmental stress that enhances pigment production. Manipulating the watering schedule is a subtle way to encourage the pink hues, as Hoyas store water in their thick, succulent-like leaves. Allowing the potting medium to dry out completely between waterings and even waiting a few extra days provides a mild, beneficial water stress. Overly wet conditions, in contrast, promote lush, green growth and inhibit the coloration.
Temperature also plays a role in the intensity of the coloration. While Hoyas prefer warm conditions generally, slightly cooler nighttime temperatures can enhance the production of anthocyanin pigments. A temperature differential between day and night, such as a drop to around 60°F, can signal to the plant to ramp up its protective coloration.
Fertilizer choice must be carefully considered because high-nitrogen formulas prioritize green, vegetative growth. To encourage pink color, use a balanced, diluted fertilizer, such as a 2-1-2 or 3-1-2 NPK ratio, sparingly during the active growing season. Reducing the frequency or strength of feeding helps shift the plant’s energy toward producing the desirable protective pigments.
Maintaining Vibrant Pink Hues
Once the vibrant pink coloration is achieved, maintaining it requires consistency in the high-light environment. If the light intensity decreases or the plant is watered too frequently, the pink pigment will begin to fade back to the creamy white variegation. The plant will also start to produce less variegated, or even solid green, leaves, which is a process known as reversion.
To combat reversion, prune any vines that produce only solid green leaves, as these sections are more vigorous and can eventually overtake the variegated growth. New growth appears on long, leafless tendrils, so avoid cutting these back unless they are completely dry or damaged. Continually monitor the foliage for signs of sun scorch, which indicates the light intensity needs a slight reduction.