Hoya Clemensiorum (How to help this RARE variety to THRIVE!)

hoya clemensiorum in a small black pot, this is an exotic tropical plant

Hoyas are one of the most commonly grown houseplants, known for their plump waxy leaves that store water.

The Hoya Clemensiorum, however, is considered a rare variety that looks quite unlike any other. 🙂 It has unusual, light green long leaves with a crisp edge and intricate dark green patterned veins. Personally, we think the veining is what makes this plant so interesting… when you see light catching the leaves, the veining almost looks like stained glass.

Leaves also have some light green speckling if you look closely enough!

Care-wise, the Hoya Clemensiorum is easy to grow, but be warned that it grows VERY slowly. High humidity (>50%) and sufficient bright indirect light are important to keep it growing well. We find that it requires an extremely gritty + chunky mix, and recommend mixing in 50% pumice with 10% orchid bark, 10% charcoal, and 30% indoor potting soil.

Let’s dive into the details.

What about the Hoya Clemensiorum Red?

There is a red-colored version of the Hoya Clemensiorum that is BEAUTIFUL… but so hard to get your hands on.

How To Care For Your Hoya Clemensiorum

Light

In our experience, the Hoya Clemensiorum needs around 6 hours of bright, indirect sunlight to grow well. More than 3-4 hours of harsh direct light (especially afternoon sunlight, when the sun is the harshest!) can burn the plant and damage its leaves.

Near a south or west-facing window is the ideal location when growing this plant indoors.

Can you grow the Hoya Clemensiorum outdoors?

Yes! If you live in USDA hardiness zones 9 to 11, you can grow the Hoya Clemensiorum outdoors in an area where it will receive diffused sunlight. Just remember that light intensity is MUCH higher outdoors (compared to indoors), so choose a spot that is away from direct light.

close up of the hoya clemensiorum leaf with intricate dark green veining

Water

Like most other Hoyas, the Hoya Clemensiorum grows best when you allow the soil to dry out a bit between waterings. That doesn’t mean, however, that you should underwater the plant and let it become water stressed. A good general rule of thumb is to water once every week.

However, you should always check to see if the topsoil is dry before watering. This will help to prevent overwatering the Hoya.

During the fall and winter months, reduce how much water you give the Hoya Clemensiorum. The goal is to water them only when the top 2inches (5cm) of soil is dry.

Humidity

Hoya Clemensiorum is a tropical plant that is native to Borneo, which has a tropical climate. This should give you a clue on the type of environment your plant would thrive in :).

On average, Borneo has a humidity level of around 80-percent, which is much higher than the average residential humidity level. The good news is that the Hoya Clemensiorum can tolerate lower humidity (50-80%), but lower humidity causes its growth rate to slow.

It is common for the air to become too dry during the colder season when heaters and fireplaces begin to pull the moisture from the air. This can cause problems for the Hoya Clemensiorum since they need do best in high humidity.

Thankfully, adding a humidifier in the room with the plant can help take care of this issue. You can also check out other ways to increase humidity levels around your plants.

Temperature

This plant needs warm temperatures throughout the entire year. Aim for temperatures between 60-85 degrees F (16-29 degrees C).

Furthermore, avoid allowing the Hoya to sit in an area where temperatures are below 55 degrees for an extended period of time as too low temperatures can shock your poor Hoya and eventually kill it.

Growth

When grown indoors as a houseplant, the Hoya Clemensiorum has a slower growth rate than most Hoya species. This one is a bit of a slow poke… Expect it to put out only 3-4 new leaves per year.

Sufficient sunlight (6 hours bright, indirect light) and high humidity (above 50%, up to 90%!) help this plant to grow as quickly as it can manage. 🙂 So it’s important to get those two things right.

New leaves are soft and flimsy, but mature leaves are tough and hard. We also like to admire the leaves’ slight serrated edges.

One thing to note – damage to leaves CAN be permanent. So handle it with care.

Flowers

Hoya Clemensiorum flowers come in clusters of yellow with reddish edges… it is known to have a musky, citrusy scent most prominent during the evenings.

Soil or Growing Medium

The type of soil or growing medium used for Hoya Clemensiorum can make or break your plant. The wrong type can quickly cause your plant to decline.

Thankfully, you can create your own special blend by mixing:

This soil mixture has good air circulation and drainage, while also retaining the right amount of moisture without being compact.

Fertilizer

Hoya Clemensiorum doesn’t require a lot of feeding, but you can help boost their growth by feeding them a gentle, liquid fertilizer that has been diluted to half its strength. This fertilizer should be applied no more than once every 8 weeks during the active growing season (spring + summer).

Hold off fertilizing in the fall and winter months.

This Hoya doesn’t do well with overfertilizing – being a slow grower, it doesn’t need it.

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08/21/2022 10:16 pm GMT

Repotting

Hoya Clemensiorum are not too worried about becoming rootbound, which means they don’t need to be repotted regularly. In most cases, you will only have to repot the plant once every 3 or so years.

When you do repot the Hoya, do so in early spring or early summer and make sure to thoroughly water the plant before repotting. This is when the plant is actively growing and much more likely to bounce back from the stress that naturally occurs during the repotting process. 🙂

Additionally, repot the Hoya Clemensiorum in a container that is only 2 inches bigger (5cm) than the current pot. Overpotting leads to too much “unused” soil that holds on to too much moisture… leading to an overwatered and unhappy Clemensiorum.

Toxicity

The Hoya Clemensiorum is non-toxic to pets and humans.

Propagation

Like other Hoya species, Hoya Clemensiorum is propagated by stem cuttings. This allows you to grow several Hoya plants from one single plant. 

The propagation should be done in the spring and summer, and the cutting should come from a healthy and mature plant. We don’t recommend propagating a plant you’ve recently bought or relocated. Let it settle into its new home before propagating.

  1. Cut a stem that is about 4-6 inches (10-15cm) long with several leaf nodes on it.
  2. Remove the bottom leaves and then plant the stem, cut side down, into the same growing medium as the parent plant.
  3. Thoroughly water the cutting and then set it in an area where it will receive bright, indirect light.
  4. Care for the cutting as you would care for its parent plant. Roots should start to form after 4 weeks.

Pruning

Hoyas handle pruning just fine, as long as it is done in the right way. Use a pair of sharp pruning shears to prune the plant, making your cuts just above a leaf node.

Prune to remove dead, damaged, or diseased leaves, or to simply control the plant’s growth and form. 

Just remember to never prune more than 1/4 of the plant’s leaves as this can be detrimental to its health. 

Common Pests and Issues

Pests

Hoya Clemensiorum doesn’t have many pest problems, although it can come under attack by common sap-sucking insects, such as mealybugs and spidermites. If you suspect your Hoya has a pest infestation, immediately quarantine the plant and then treat with insecticidal soap or neem oil.

Additionally, you should also examine your other houseplants and make sure the pests haven’t spread to them as well.

Overwatering

As for diseases, Hoya Clemensiorum is susceptible to overwatering. Because this plant is considered a semi-succulent, it stores excess water in its foliage, so it doesn’t require as much watering as a plant that doesn’t have plump leaves.

The good news is that overwatering is completely preventable and you should simply let the soil dry out a little between waterings. 

Troubleshooting

Why are the leaves on my Hoya Clemensiorum turning yellow?

Overwatering will cause your Hoya Clemensiorum’s leaves to start turning yellow. They may also begin to wilt and even fall off the plant.

If the problem isn’t corrected, the overwatering will lead to root rot. Root rot is a fungal disease that should never be taken lightly. It is extremely difficult to get rid of and will most likely kill the Hoya Clemensiorum.

Why isn’t my Hoya Clemensiorum growing?

If your Hoya Clemensiorum isn’t growing, it is probably not receiving the right care. Slow or stunted growth is one of the most common symptoms of a plant not getting its needs met.

Unfortunately, there is no way to determine which needs are being neglected. That is why it is vital to ensure the Hoya is growing in the right light, soil, temperature, and humidity level, while also giving the plant the proper amount of water. 

What could cause my Hoya Clemensiorum leaves to turn brown?

There are several reasons as to why Hoya’s leaves turn brown. The most common reason, however, is that the plant is underwatered.

If you confirm that this is the cause by feeling the leaves to see if they feel dry and crispy, as well as examine the soil of the plant. If the soil is dry and pulling away from the pot, then the culprit is underwatering the plant. 

Frequently Asked Questions

Should I mist my Hoya Clemensiorum?

Some articles suggest misting can help keep the Hoya Clemensiorum hydrated during dry periods, while also increasing the humidity level around the plant. However, we don’t recommend misting, as the effect is very minimal, and wet foliage can lead to fungal and bacterial growth, which is not worth the risk!

If you want to raise humidity levels, use a humidifier.

How long can Hoya Clemensiorum go without water?

Because Hoya Clemensiorum is a semi-succulent, it can go without water for weeks. That doesn’t mean, however, that you shouldn’t water the plant when it needs hydration.

Underwatering any plant can cause unnecessary stress, which makes it more susceptible to pests and diseases.

Instead, you should water your plant when the top 2 inches (5cm) of soil is dry. How often this is exactly depends on your climate, the season, temperature, and growing medium… so it’s impossible to say precisely. That’s why checking the moisture levels of the topsoil is so important!

Can I take my Hoya Clemensiorum outside?

Hoya Clemensiorums are hardy in USDA hardiness zones 9 to 11. For people outside of these zones, the plant will need to be grown indoors.

However, when temperatures are between 60-85 degrees F (16-29 degrees C), you can take the plant outside and give it some fresh air. Just make sure that the plant is still protected from the harsh sun, as well as damaging rain and winds. And don’t forget to bring the Hoya Clemensiorum back inside before temperatures start to dip below 60 (16 degrees C). 🙂

Wrapping Up

As you can see, the Hoya Clemensiorum is an easy-going plant that needs just a little care to be happy.

Warm temperatures, high humidity levels (50-90%), watering when the soil is dry, and bright indirect light is really all this Hoya plant needs to live for many years. The hardest part is waiting for this slow poke to grow 🙂

Deborah is a plant enthusiast and founder of Gardening Collective.