Hoya kerrii, also known as sweetheart plant, heart leaf hoya, wax hearts, and Valentine’s hoya, is one of the most instantly recognizable succulents out there. It has large, heart-shaped leaves that are often potted upright individually and sold around Valentine’s Day as gifts.
These plants are epiphytes that grow attached to other plants, though they aren’t parasitic. They just use other plants as a support structure so they can access moisture and nutrients above the ground.
Most people opt to grow them in traditional potting soil, but you can also mount them if you choose.
- Genus: Hoya
- Species: kerrii
- Native To: Southeast Asia (Cambodia, Java, Laos, Malaysia, Thailand, Vietnam)
- Sun Exposure: Typically bright indirect or diffused light
- Soil Preference: Well-draining loam or bark and moss
- Soil pH: 6.0.7.5
- Blossom Color: Burgundy
- Toxicity: Non-toxic, though sap may cause skin irritation in sensitive individuals
Caring for Hoya kerrii:
Native to Cambodia, Java, Laos, Malaysia, Thailand, and Vietnam, this plant grows attached to trees and shrubs in the warm, humid forests of Southeast Asia.
In the right conditions, this plant will send out star-shaped, burgundy flowers with five waxy petals at the end of peduncles.
This plant could be called sweetheart vine based on the fact that it takes its sweet time growing. Don’t feel like you’ve done something wrong if it doesn’t add new leaves every month. This is a slow-growing vine.
While they can tolerate brief temperatures out of their preferred range of 60-80°F, don’t allow them to be exposed to anything below 45°F at any point. Exposure to temperatures this low might harm or even kill the existing foliage. Anything below 32°F will kill the plant as it’s not frost tolerant.
Don’t place your hoya near a drafty window or an exterior door. You should also avoid heat and air conditioning registers.
Sweetheart hoyas are adaptable when it comes to humidity. Anything from 20-60% is fine, and this is in the range of most homes.
If your home is extremely dry, try grouping plants together or keep them in the bathroom. You can also purchase small humidifiers meant to keep a few nearby houseplants in optimal humidity levels.
Light
Sweetheart hoyas are pretty easy to please in terms of light. They can adapt to just about anything, so long as it isn’t extremely dark or in direct afternoon sunlight. Morning sun is fine, but afternoon and evening light tends to be too strong.
Ideally, situate the plant in a north-facing window or near a west, east, or south-facing window but out of any direct sun. If the plant does receive some light, make sure it’s not more than two or three hours per day.
You’ll know if the plant is receiving too much light if the leaves begin to turn yellow or pale green. Leggy or slow growth is a sign that they aren’t receiving enough light.
If variegated types don’t receive enough light, they will revert to solid.
Soil
While this plant can adapt to all kinds of different light and humidity levels, it’s pretty intolerant of the wrong kind of soil. While single hearts might be fine in potting soil, grow your plants in a cactus or succulent mix.
Hoyas are sensitive to wet roots. If you imagine how the plant grows in nature, clinging to the bark of a tree or something similar, you can see how it hasn’t adapted to lots of moisture around the roots.
A cactus or succulent mix is light enough that it allows water to drain away quickly.
If you decide to mount your plant, you can use sphagnum moss as the base for the roots.
When you buy a single-leaf hoya, it might be glued or otherwise mounted onto a log, rock, piece of wood, or something else unsuitable for long-term growth. If that’s the case, gently remove it and place the fruits in suitable soil.
Water
The thick leaves of Hoya kerrii are excellent storage containers for moisture, which means that this plant can tolerate some drought.
Whichever medium you choose, you should only add water when it has dried out completely. Don’t assume that you can water on a schedule, such as once per week.
Every home has different humidity levels, and fluctuating temperatures change how much water is retained in the base medium. You might end up watering once a week in the winter and every other day in the summer. Or you might water only once a month in the winter and once a week in the summer. It all depends on your individual circumstances, which is why checking how wet or dry the medium is before watering is crucial.
Water at the soil and not on the leaves. This can be a challenge if your plant has a thick base of leaves, so you might need to use a watering can or pitcher with a long, narrow lip.
Be sure to empty any catchment container 30 minutes after watering.
When watering mounted plants, be sure to soak the moss thoroughly. Large houseplant misters with long nozzles are an effective tool for soaking moss without dripping excess water all over the place.
Feeding
No need to fertilize Hoya kerrii. These plants thrive in depleted soil. If you feel that your plant isn’t doing as well as it should and you want to give it a boost of nutrients, use something with a low NPK rating. A mild, balanced fertilizer with a 1-1-1 or 3-3-3 NPK rating will work fine.
Feed the soil in the spring.
Potting or Mounting
If you opt to grow in a container, it must have a drainage hole for water to run out of. Terra cotta or unglazed ceramic is an excellent material choice because it allows for better water evaporation than glazed ceramic or plastic.
When it comes to mounting, so long as the roots are wrapped in a base of sphagnum moss, you can attach the moss and roots to anything you like. Many people choose a log or wood because it has a natural appearance that complements the plant, but you could use a rock, a piece of plastic, or a piece of glass if you choose.
Whatever you opt for, it should be able to dry out between waterings and not hold water against the roots.
To mount your plant, remove it from its existing container and brush or wash away most of the soil. Then, wrap the roots in several inches of sphagnum moss. Secure this in place with twine or string.
Attach the ball to your chosen material using nails, screws, glue, or additional string, as desired.
Maintenance
The most important part of maintaining Hoya kerrii is wiping the leaves regularly with a damp cloth to remove any dust. Dust build-up limits the plant’s ability to respirate and photosynthesize.
Trim off any dead, damaged, or unsightly leaves. You can also trim a vine to encourage more branching at the base and limit the length of the vine.
As these plants grow, they send out long, leafless vines. These will eventually develop leaves, though it can take a while. Don’t prune them off.
Similarly, if your plant has bloomed before, don’t cut off the bare peduncle after the flowers fade. This is where the plant will develop new blossoms, and so you don’t want to remove it.
If you want to encourage your plant to bloom, make sure it has direct light for part of the day. You should also expose it to at least 10 degrees cooler temperatures at night than during the day.
You can allow your plant to trail gracefully over the side of a container, or you can train them up poles, trellises, or sticks.
These plants don’t form suckers or tendrils to attach themselves to structures, so you’ll need to weave the vine into the structure or secure it using twine or string. Be sure not to tie the string or twine too tight, or you will cut off circulation.
When the plant develops aerial roots, you can secure these to the structure using twine or string.
Re-pot your plant every few years in the spring, unless the plant is flowering. You’ll want to choose a container one size up from your existing container. Remove the plant from its pot and brush away the soil from the roots.
Re-pot it in fresh, clean potting soil.
Even if you don’t go up a size of pot because your plant hasn’t grown large enough for re-potting, you should change the soil out completely every five years or so. Old soil becomes depleted of nutrients, compacts, and can become hydrophobic, which means it repels rather than absorbs water.
Best Cultivars
There are a few cultivars of the Hoya kerrii species, though they can be somewhat of a challenge to pin down.
Albomarginata
H. kerrii var. ‘Albomarginata’ is a naturally occurring variety of the species. That means it wasn’t developed by human intervention but happened naturally. This variety has leaves with a large green center and creamy yellow margins.
Albomarginata Reversed
If you guessed that this variety is just like ‘Albomarginata’ but with a cream center and green leaf margins, you’re right. It’s sometimes sold as a “reverse hoya,” and it’s extremely rare. If you find it, be prepared to pay good money for it.
Splash
‘Splash’ is a cultivar that was developed to have silvery-gray splotches and spots on a green base. If you’ve ever seen a merle Australian shepherd, the coloration is often compared to that. The leaves are the same size as the species but with their unique coloration.
Propagation
Hoya kerrii can be propagated by taking leaf cuttings, by taking stem cuttings, and by layering.
Keep in mind that if you propagate a leaf cutting, unless you include some stem tissue, your plant will never develop new vines and leaves. It will remain a single leaf, and it will likely only survive for about five years at most. But that’s how most of these plants are sold, and it’s undeniably cute, so feel free to give the process a try.
Before we jump in, let’s clarify a few terms. The leaf is the big, heart-shaped part, and it’s attached to the main vine by a petiole. On the vine, you will see two kinds of nodes. The first is a leaf node, which is a little bump where the leaf will emerge. You can usually identify these because they’re the same color as the rest of the vine, and you can usually see a tiny leaf emerging.
The second node is the root node. Because these plants are epiphytes, they develop aerial roots along the vines that can latch and help anchor them onto their host tree. These root nodes are usually lighter in color and may develop a small lump.
To take a leaf cutting, cut off a leaf from the vine using a clean knife. Cut just above the petiole if you don’t mind a single leaf, or cut including the petiole and a little bit of the stem if you want a plant that will vine.
Insert the cutting into equal parts sphagnum moss and perlite.
Keep the moss moist at all times. Don’t let the medium dry out. Some people like to place a glass or cloche over the cutting to help keep some moisture in, others just check the plant several times a day.
Within a few weeks, new roots should have developed.
Stem cuttings are similar to leaf cuttings, only you’re including a section of the vine with at least two leaf nodes and one root node. Remove the bottom leaf and bury the node in the sphagnum mixture.
Layering is the easiest of these techniques. Take a vine with at least one root node on it and pin the root node into some potting soil using a paper clip or some wire. Keep the soil moist where the node touches the soil. Hoyas do this on their own in their natural environment, and we can simply re-create the process. To make things even easier, use a second pot filled with soil rather than layering in the existing pot.
New roots will emerge out of this spot within a few weeks. At that point, you can cut the rooted vine away from the parent. If you layered in the existing pot, gently remove the roots from the soil. Plant it in its own container.
If you propagate by one of these methods, remember that this plant can be slow-growing. It might take a while for your new wax heart to establish itself.
Common Problems, Pests, and Diseases
It’s rare that you’ll experience any problems with these plants beyond root rot if you overwater. It’s not impossible, however, especially if your plants are stressed due to under or overwater or too much or too little light.
Aphids, mealybugs, and scale are all common houseplant pests that will feed on hoyas. You will be able to see the insects feeding on your plants or you might notice yellowing leaves, first. Aphids can be sprayed off the plant with a steady stream of water. Mealybugs and scale can be gently scraped off using a butter knife.
Root rot shows up as soft, soggy, yellowing leaves. By the time the foliage is involved, the roots are typically far along in their rot. As soon as you notice the symptoms, remove the plant from the soil and knock or wash away as much of the soil as you can. Cut off any mushy, black, or rotten roots. Clean the pot and re-pot the plant in clean, fresh potting soil.
Be careful not to overwater going forward, and make sure the water is draining out of the container.
Mounted plants rarely experience root rot.
