She may be hard to find, but the Hoya Krimson Princess is adding more pink to more households. The plant was popular in the United States from the 1960s to the 1980s and has rebounded in recent years.
The Hoya Krimson Princess (or Hoya carnosa ‘Rubra’) is a vine with green and pink leaves. It loves bright indirect light, warmth, high humidity, and well-draining soil. It also survives in medium light and humidity, making it friendly for beginners who want a pink plant for their household.
Here is an in-depth guide on the Hoya Krimson Princess and how to care for it.
|Common Name||Hoya Krimson Princess, Hoya Rubra, Hoya Picta, wax plant, porcelain flowers|
|Scientific Name||Hoya carnosa ‘Rubra’, Hoya carnosa ‘Picta’|
|Family||Apocynaceae or the dogbane family|
|Origin||They come from across the Australasia region, from Australia to India and China.|
|Growth||Hoya Krimson Princesses are succulent, woody climbers. In optimum conditions, they reach between 4–6 ft (122–183 cm) long. Leaves grow 1.5–2 in (3.8–5 cm)|
|Flowering||Small pink to white star-shaped flowers arranged as an umbel or an inflorescence roundly clustered and meet in the middle. They bloom at night from late spring to summer.|
|Scent||They are often associated with chocolate, vanilla, and honey scents.|
|Ease of Care||They are perfect for beginners.|
|Soil||They need well-draining soil, particularly with additions like bark and perlite.|
|Light Requirements||Inside: They grow best with bright, indirect light. Outside: Keep them in partial sun and sheltered from the wind.|
|Watering Needs||Water them thoroughly until draining, then wait until the first 2 in (5 cm) become dry.|
|Temperature||They prefer 59–82 °F (15–28 °C).|
|Humidity||They survive in 40–60% humidity, which is typical household humidity. But Hoya Krimson Princesses grow best in 70-80% humidity.|
|USDA Hardiness||Outside, they will grow in zone 10–11.|
|Potting||Repot in the spring whenever roots try escaping out the drainage holes or above the soil. Use a pot size that’s another 1–2 in (2.5–5 cm) wider in diameter than the previous pot.|
|Fertilizer||You fertilize while watering with a balanced formula diluted to ¼ once a month in the spring and summer.|
|Propagating||You propagate Hoya Krimson Princesses by stem cuttings.|
|Care Problems||Be wary of overwatering. The signs include wilting leaves, yellowing leaves, and dark and mushy stems.|
|Pests||Common pests include aphids, gnats, mealybugs, scales, spider mites, and thrips.|
|Toxicity||These hoyas are not toxic, but their sap may irritate your skin.|
Origins, Appearance, and Growth
The Hoya Krimson Princess or Hoya carnosa ‘Rubra’ is a member of the Apocynaceae family. In 2012, its former family, Asclepiadaceae, became a subfamily of Apocynaceae. With recent recategorizations like this, you’ll often still see a plant associated with an older name.
It comes from the native Hoya carnosa of Australasia, ranging from Australia to India to China. It was named after the Northumberland duke’s gardener, Thomas Hoym, in the 1700s.
The species has thick waxy leaves and woody stems, and it grows in trees other known as epiphytic. But many of its relatives are the opposite. They grow thin leaves, herbaceous stems, and in the ground.
Indoors, Hoya Krimson Princess grows to 80 in (2 m). The ovate to elliptical leaves grow 2 in (5 cm) long. Their vine-like growth habit makes them ideal for draping around objects in your home, with a trellis or stakes, or in hanging baskets.
While the Hoya Krimson Princess is a worthy indoor plant because of its colorful leaves, it is also known for its flowers. Once the plant has a few years to reach maturity, good light, and enough humidity, it blooms.
The pink inflorescence is an umbel, a ball-shaped cluster of up to 30 individual flowers attached at the center. They have a fuzzy light pink to white five-pointed star-shaped petal. Within that is a concentric smooth five-pointed petal of light pink that turns dark at its center. Their nectar smells strongest at night and can resemble honey, butter, or chocolate.
If you have a plant that has already flowered, leave the peduncle rather than clipping it back after blooming. Hoya Krimson Princess reuses the same flower bases over and over.
You may value the flowers so much that you may want to install grow lights. These allow plants to develop flowers even on indoor plants that would otherwise rarely bloom. A humidifier to get 70–80% humidity also helps with blooming. If you fertilize your plants, using a phosphorus-based product will support blooming best.
The Hoya Krimson Princess needs well-draining soil. As an epiphyte, it would naturally grow above ground using moss, bark, and soil trapped in these materials.
The indoor hoya needs similar soil. Perlite, coco coir, and orchid bark absorb and slowly release water. This substrate lets the plant roots have moisture but also breathing room. These materials also create larger air pockets that encourage draining.
You can also not use soil but LECA or lightweight expanded clay aggregate. You may have seen these brown spherical pebbles in plant displays at businesses.
The Hoya Krimson Princess likes bright, indirect light.
As a variegated plant, it needs more brightness to show strong colors. Hoyas tolerate lower light, but you won’t see as much color contrast or saturation.
Plants growing in low light will become leggy, meaning they’ll have longer stems between leaves because they’re reaching for more light.
Yet, they also turn brown and crisp in direct light, like from a prolonged western, unfiltered exposure. Hoya Krimson Princesses are fine with a few hours of direct light, but not much more. East-facing windows are less harsh.
Some distance or a barrier like sheers helps even more. Some grow lights, like LEDs, allow a full spectrum of wavelengths similar to the sun but without the risk of burning or needing to be next to a window.
When watering a Hoya Krimson Princess, check to see if the first several inches are dry. If not, wait. If so, water until it starts to drain into the drainage pan. Watering like this gets moisture as evenly as possible throughout the pot so that all roots have access.
Dump the water that fills the drainage pan. It may look like it’s not in the pot affecting the plant, but water likes to find an equilibrium. It also wicks. So if there’s water in the saucer, there’s excess water in the pot drowning the roots.
The warmer the conditions, like time outside during the summer, the more your plant will want. Watering in the morning will also give the plant what it needs to drink while letting the daylight evaporate excess water.
Hoya Krimson Princesses can be sensitive to water on their leaves. If you notice rough spots on the leaves, try watering them at the base of the plant.
Tropical roots also can experience shock when watered with cold water. When in shock, the plant may drop its leaves. Use lukewarm water to avoid this issue.
The waxy leaves store more water than non-waxy leaves. If you see the leaves, especially the lower ones, wrinkle or shift into a cup shape, the plant needs more water. Yellowing and softening leaves are other indicators of needing more water.
Temperature and Humidity
Hoya Krimson Princesses do best in 59–82 °F (15–28 °C) and 70–80% humidity. They’ll tolerate temperatures between 50–100 °F (10–38 °C) and the typical household humidity of 40–60%, but they’ll grow less and appear less vibrant. They also drop their leaves when they get too cold, even if the cold is a draft from an air conditioning vent.
To create more humidity, keep the plant in a bathroom, near a humidifier, or on a wet pebble tray. Alternative to a pebble tray, you can find a larger pot you like, put rocks on the bottom, and insert the plant’s pot inside. The air spacing of the rocks assures that the hoya’s roots aren’t sitting in water.
Occasional misting also helps with humidity. The mist droplets collect into the flowers and can ruin the petals. If you want to mist, limit it to when the plant isn’t flowering.
Another approach is to keep your Hoya Krimson Princess close to other plants. Plants have wet breath like people. But in their case, if many reside close together, they create a microclimate.
Hoya Krimson Princesses like living almost root-bound and minimally handled. So, when picking a pot, use one where the roots can grow just a little, like in a pot that is 1–2 in (2.5–5 cm) greater in diameter than the last pot.
Let the roots crowd and stay crowded rather than get repotted frequently. Smaller pots also mean there’s less space for water to sit and develop fungi or bacteria.
There are signs when it’s a good idea to repot:
- Overcrowded: Roots show through the drainage holes or pop out of the top of the soil.
- Yellowing leaves: This might be a sign of root rot. The best treatment is to use fresh soil, or in other words, repot.
And there are signs when it’s a bad idea to repot:
- Flowering: The Hoya Krimson Princess is more susceptible to shock while flowering.
- Dormancy: Plants need to rest during the winter. Wait until spring to repot.
When repotting, water your hoya thoroughly to lessen its stress and make it easier to remove. Particularly if the roots are growing out of the bottom of the pot, it’ll take some teasing to get it out without damaging the roots.
The new soil should be watered to make it as comforting as possible to the hoya during the transition. Also, loosen old soil before you place the plant into the new pot.
If you intend to fertilize your Hoya Krimson Princess, a liquid organic fertilizer. Dilute it by half and apply it around once per month in the spring and summer when you water. Using fertilizer too often, during the winter, or with too high a concentration can burn the plant.
For the best blooming chances, a fertilizer higher in phosphorus compared to nitrogen and potassium helps. So, the NPK number might be 2:3:2 or 2:3:1. If you’re using LECA as a substrate instead of soil, you’ll need a hydroponics fertilizer.
You can propagate Hoya Krimson Princesses from stem cuttings during the spring or summer. Cut a green, non-woody vine with at least two leaves on the upper end of a 5 in (12.5 cm) stem with sterilized shears. To sterilize the blades, submerge or wipe them down with rubbing alcohol.
For the best results, buy root hormone so that you can dab the base of the cutting into the hormone.
Soil, water, LECA, and moss work as support for a cutting until it grows roots. For soil propagation, you treat the cutting like a full-fledged plant that you repot: place it in a pot with moistened, well-draining soil. The other propagation methods grow roots in other mediums and then transition to the soil.
Regardless of the method, growing new roots takes a few weeks. Wait for the roots to grow around one inch (2.5 cm) before transferring them to soil from another medium. The new leaves take a few months to start growing.
For water propagation, place the lower stem into a jar of clear, lukewarm water. You use something like chopsticks to keep the base of the stem from touching the bottom of the jar. The water needs to be replaced when it’s no longer clear.
With LECA, you place an inch of wet LECA into a clear jar, then place the cutting, and add some more LECA for support. The bottom of the cutting should be just out of reach of the water since the LECA will distribute moisture.
Propagating with moss is like using a sponge as a growth medium. You wet it and wring out excess water. Unlike using a sponge, with moss you need to add and mix in an aeration component like perlite or vermiculite. You’ll also need to keep the moss moist for several weeks. A plastic containment like a box, bag, or wrap with a few air gaps will retain more moisture.
Mealy bugs, scales, and spider mites are attracted to Hoya Krimson Princesses, especially if the plants are blooming. Spray some neem oil on a cloth and wipe down your hoya to get rid of a minor infestation. Pay extra attention to the underside of leaves where these insects like to hide.
Signs of each sapsucker:
- Mealybugs: Mealybugs are white, fuzzy, and oval. They hang out on the newest growth of a plant where the tissue is softest. They are more likely to attack overwatered and over-fertilized plants.
- Scales: Scales are flat, oval insects with brown patterns that gather on stems and petioles.
- Spider mites: Spider mites appear as black specks to the naked eye and are most easily identified by the webbing they create. They also eat chlorophyll and leave white to yellow spots on leaves.
All three insects are more likely to infest your Hoya Krimson Princess if conditions are warm and dry. When mealybugs and scales feed, they also dribble a dew that grows fungi.
Less common pests include aphids, caterpillars, gnats, and thrips. They don’t infiltrate a household often, but they may infest your Hoya Krimson Princess if you keep it outside.
Hoya Krimson Princesses are prone to root rot, a fungal infection. It grows when a plant spends too much time with its roots in water as opposed to healthy, moist but drained soil. Or in other words, when there’s too much water compared to air, the fungus takes hold.
One early sign of root rot is shriveled yellow leaves. The waxy texture of a hoya leaf takes more time than most to wilt, so the disease may advance farther before you notice. At this stage, limit your watering routine and pay closer attention to when the first several inches of soil dry. Early root rot means you’ve been overwatering consistently, and that’s a habit you can fix.
In severe cases, the stem base will turn brown and feel mushy. At this point, the roots will already be black and dead. If your hoya has a chance at survival, it’ll be because you clipped any dead roots and repotted the hoya in new soil. Give the plant a fresh start. Sometimes though, the rot is too advanced, and the hoya dies.
The Hoya Krimson Princess is nontoxic to people and pets. But you may have a skin sensitivity to its sap. If this concerns you, use gloves when handling your plant.
Confusion Over Krimson Princess and Krimson Queen
There are two Hoya Krimson royals. If you hear about a Hoya Krimson Queen, you’re hearing about a different Hoya carnosa with a similar name and appearance.
One pronounced difference makes it easy to identify the plants. Hoya Krimson Queen has its pinkish variegation on the outer rim of its leaves. It also has brown stems. The Hoya Krimson Princess has variegated colors in the middle of its leaves, and it has pink stems.
Because of their color differences, Hoya Krimson Queens have more green to support faster growth. More growth also requires more watering compared to the slow-growing Hoya Krimson Princess.
You can grow your Hoya Krimson Princess outside and go for the flowers or grow it indoors for just the beautiful leaves. Either way, you should know what you need to see a healthy plant.
If you have non-variegated hoyas, don’t be alarmed if those grow faster and need less sunlight than the Hoya Krimson Princess. This is because non-variegated leaves have a greater green surface area to photosynthesize.