Hoya Imperialis is a spectacular out-performer out of all the Hoyas that I’ve seen in my years as a gardener.
This vine of Malaysian origins is a rampant grower that’s very hard to keep under control, creeping and climbing over anything it can find and throwing out umbels and umbels of the most gorgeous maroon waxy flowers throughout the year.
Most gardeners grow Hoya Imperialis for its otherworldly blooms – maroon to mauve, perfectly star shaped, like wedding cake decorations.
They even have a sweet fragrance of spices about them. The leaves are a lush glossy green. According to the University of Connecticut, Hoyas are great air purifiers good at absorbing harmful volatile organic compounds.
That said, I would think twice before I grow Hoya Imperialis indoors because it does get quite big! Now that is not to say it’s an easy, low-maintenance plant.
In fact, it can be quite a fussy one. Hoya Imperialis care involves knowing what fast-growing, evergreen, tropical vines need viz. warm temperatures, plenty of light, humidity, etc. all of which can be managed even in indoor environments of cold-weather regions. Read on for more details.
Table of Contents
HOYA IMPERIALIS CARE INSTRUCTIONS
Soil
The right soil for Hoya Imperialis care is one that’s rich in organic nutrients and is extremely well-draining.
Hoyas are epiphytes occurring in tropical rain forests of Southeast Asia where they don’t necessarily grow in a soil substrate in their natural environment and draw nutrients from the air, rainwater, forest debris collected around the roots, and decomposing bark of the host trees.
Grow Hoya Imperialis in a potting mix with more than 50% of organic clumps like bark bits, charcoal, chunks of coco-husk or sphagnum moss, and the other 50% of perlite.
This will give the roots just what they want – excellent drainage, aeration, moisture retention, and something to bind themselves around.
An easy Hoya Imperialis care hack is to use a store-bought orchid medium. To this, you could add perlite, bark, or charcoal bits and give the overall mix a rough, chunky texture like oatmeal muesli.
Light
The right amount of light is an important part of Hoya Imperialis care. “Bright shade” is what they prefer but not direct sunlight. In the northern zones, you can grow
Hoya Imperialis by south-east or a south-west window. In the hardy zones, it’s better to place the plant where there is no direct sunlight but bright nevertheless. For eg. feel free to grow Hoya Imperialis in your patio in a medium-light spot.
You should move your plant indoors for outwintering; they’ll do just fine even under LED grow lights for 10-12 hours a day.
Although common knowledge is that Hoyas stop flowering in winters, under grow lights they have been observed to bud up even in the cold months.
Watering
Hoya Imperialis care requires consistent watering compared to other Hoyas but it doesn’t like to sit in water.
It’s more of a tropical evergreen than a succulent. I grow Hoya Imperialis with a once-a-week watering cycle during summer ensuring that the roots dry out between waterings – not just the topsoil, but all the way down – this is a very important part of Hoya Imperialis care and the most common cause of its death.
Slightly lift the pot before watering. If it feels heavy it probably isn’t dry yet.
If your plant is very young it is more susceptible to root rot. A large mature plant can cope with watering mistakes.
Grow Hoya Imperialis in a somewhat small pot that naturally limits the water available to the roots.
Pro-tip: Make sure you water deeply, saturating the root-ball and not in sips, to avoid build-up of mineral salts – a very important aspect of Hoya Imperialis care.
Empty your drip trays after the excess water drains out.
Finally, watering is closely linked with soil when you grow Hoya Imperialis particularly if you’re growing this indoors. So, get the soil proportions right first of all stressing on it being well-draining.
Temperature
There’s a lot of internet material that gives rather confusing temperature ranges for Hoyas.
This is because Hoya species have widely ranging warmth requirements. Some Hoyas like the Hoya Lacunosa and Hoya Carnosa need cool temperatures 50°F – 75°F (10°C – 25°C).
Most in the genus including Hoya Imperialis care require intermediate range temperatures 60°F – 95°F (15°C – 35°C).
In my experience, you can grow Hoya Imperialis at the lowest continual temperature 60°F (15°C), but the plant will be the happiest at temperatures over 95°F (35°C) for extended periods of time.
They are not frost tolerant. This is why, despite their rampant growth pattern, I would still recommend growing Hoya Imperialis indoors or in a plant house in comfortable room temperatures if you live in cold regions. Growth may slow down but it’ll survive.
Then there are the warm temperatures types that suffer in the slightest chill and need continual temperatures above 70°F (21°C), for e.g. Hoya Pachyclada.
Humidity
Humidity wise Hoya Imperialis care is fairly straightforward. These plants belong to regions with moderate to high humidity and could do with a minimum of around 50% and do very well in the 60-70% range.
If you want to grow Hoya Imperialis in cold country winter months are going to be a challenge.
The Sahara-like dryness in aircon rooms are not great for Hoya Imperialis care, so take measures to improve humidity, such as a humidifier.
Soon you’ll understand that these plants are pro-humidity and not necessarily heavy watering.
Fertilizer
My preferred feeding method to grow Hoya Imperialis is to go heavy on organic content right at the time of potting and then following it up with a balanced liquid fertilizer.
The reason I prefer organic feeds over chemical fertilizers, particularly for epiphytes like Hoya is that they are slow-release.
This plant does seem to respond well to feeding. I don’t completely stop feeding in winter, I simply cut down the frequency to half or less.
A Hoya Imperialis care hack is to give it a good orchid fertilizer during the growing months.
This is to induce blooms and again, I prefer using a liquid organic type that’s easy to dilute and doesn’t cause the build-up of harmful salts in the soil. Water well along with feeds.
Propagation
You can propagate and grow Hoya Imperialis from herbaceous stem cuttings. They take root quite readily and reach a flowering stage within about two years from cutting.
My favorite method for propagating Hoyas is through layering and this is indeed my preferred way because it is non-intrusiveness.
However, this method isn’t easy when it comes to Hoya Imperialis care because its vines are too stiff and snappy.
I’ve made a surprisingly positive discovery with respect to propagating Hoya Imperialis, and that is water rooting. More details later.
Professional growers are known to allow pods to dry on the plant, break open to collect seeds and propagate them through germination. But the seeds do not store well and need to be sown as soon as possible.
Growth
If you want to grow Hoya Imperialis in the greenhouse or an open area, remember that this is a bit of a wild child. It will take over everything.
Within just a couple of years, the chances are that your Imperialis is several feet long. Under the right Hoya Imperialis care conditions, this trailing vine is going to grow so fast and wide that within a few years you’ll be following the vines to get to its base.
In fact, a great way to grow Hoya Imperialis would be to let it climb freely along with a garden pergola or a patio if you live in the hardy zones.
These are technically “climbing vines”, but I grow Hoya Imperialis in a mounted pot.
The ideal Hoya Imperialis care hack is to stake the pot with strong support like a trellis and hold up the stems with twisty tapes or clamps.
Twist stems back around the trellis or the older stems when they are still young. They stiffen fast as they get older and tend to break very easily.
Here’s a useful Hoya Imperialis care hack is to make it flower soon. Let it grow vertically upwards until about two meters high and then train it to creep horizontally.
When it starts growing horizontally it will start flowering as well. This the plant’s way of “reading the room”.
Hoya Imperialis has one of the biggest individual flowers in the genus. Each flower can get as big as 9 – 10 cm (3.3 – 4 inches) wide. They flower abundantly and generously once mature.
Pruning
Don’t prune the peduncles of dried flowers of a Hoya because the plant produces new flowers from the old peduncles.
A lot of people tend towards occasional pruning, particularly of dead flower heads. This would be a mistake since you grow Hoya Imperialis for the flowers. This plant lives to bloom.
By cutting away the flower stalks you’re making it work extra hard to produce fresh flower heads.
Potting
A good Hoya Imperialis care hack would be to pot the plant in a netted pot placed inside a liner pot. The netted pot ensures thorough drainage.
Once the roots grow out a lot you can simply transfer this netted pot into a bigger netted pot. This way you save yourself a lot of trouble during repotting.
Netted pots are a great way to manage soil moisture too which is the most crucial aspect of Hoya Imperialis care.
Unlike the smaller varieties of Hoyas that like to be root bound, Hoya Imperialis care would need a little more space for the roots to grow out.
Even though a smaller pot ensures less water, this is after all a fast grower and needs more of everything! That said, don’t grow Hoya Imperialis swimming around in a large pot. A good measure is to start in a 10-inch pot and add 2 inches after two years.
Hoya Imperialis Care
HOYA IMPERIALIS PROPAGATION EXPLAINED STEP BY STEP
Hoya Imperialis propagation through stem-cuttings
- Wait until June, just ahead of the growing season in the tropics. Use a healthy herbaceous tip cutting from a bug-free mother plant.
- It must have about 3 leaf nodes. Pluck off the leaves from the lower node.
- Let the cutting rest for a day until the cut forms a callous.
- You can use rooting hormone powder but it normally sprouts even without.
- Pop it in a good soil mix with good draining (can’t stress draining enough) in a 4-inch pot. 50/50 peat and perlite is a simple and effective rooting soil mix.
- Keep the mix moist but not wet and never let it dry out. Keep the cutting in shade until the plant establishes itself.
- Pro-tip: Group the pot along with other plants. This gives the cutting shade and much-needed humidity.
- Don’t disturb the cutting until established
How to propagate Hoya Imperialis through water rooting
This method has proved to be quite successful for Imperialis given it’s thin vines.
- Take a few fresh cuttings of a healthy step tip with about 4 to 5 leaves.
- Take a tall glass jar that’s 3/4th as tall as the cutting – a jam jar works.
- Fill it up with dechlorinated water or RO water and add a single drop of a good liquid rooting concentrate.
- Place your cuttings in this jar and keep it undisturbed in a place where the temperature is maintained between 75°F – 95°F (25°C – 35°C)
- It takes anywhere between 2 weeks and a month for the roots sprouting out of the nodes.
- Once the roots are about an inch long and strong transfer them into potting soil.
A smart Hoya Imperialis care hack is to keep propagating your plant and producing several baby plants as and when possible. Not every attempt will be to be successful. But this is your best hedge against winter losses.
COMMON PROBLEMS WITH HOYA IMPERIALIS
Not flowering: For those of you who grow Hoya Imperialis for the blooms this could be disappointing. The typical reason for this is too little light.
The other reason is obviously a soil poor in nutrients. If it’s a soil problem adding a balanced orchid meal to the potting mix should help.
However, my first advice would still be to give the plant enough brightness, preferable a lot of indirect sunlight, and to be patient!
One Hoya Imperialis care hack you could try is to make it creep horizontally. It tricks the plant into believing that it’s time to flower.
Individual leaves or stems shriveling and falling off: Examine the underside of the leaf. If you see fuzzy white bugs stuck to the leaf this is a mealybug infestation.
Your best defense against these bugs is to keep checking the plant regularly, especially the underside of the leaves.
If I see that characteristic tiny white cottony bug stuck under a leaf, I just spray a fine jet of water and blast it off the plant.
Now if you’ve managed to let the bug spread into an infestation, the first step is still to clean the plant thoroughly with a water jet.
Things to watch out for – don’t drench the potting soil, don’t contaminate nearby plants with blasted bugs. So it’s best to carry out this operation far away from everything else.
After your plant is thoroughly cleaned up with no visible mealy bugs anywhere, you can treat it with a commercial insecticide or an organic soap spray.
If the infestation is limited, use an alcohol swab with an earbud and apply on each bug. Time-consuming, but effective.
White dusty webby coverings along with leaves and stems: This is due to spider mites that thrive in dryness. One preventive measure is to keep up the humidity around the plant.
Choose a watering day to give your plant a thorough bath, washing down all the leaves and stems. Do this in the morning and leave the plant in a well-ventilated spot to dry out during the day.
Leaves discolor and fall off suddenly: This could be due to cold exposure. Just bring the plant indoors.
Hoyas are fairly resistant to pests but I would recommend regular application of horticultural oil or neem sprays as part of the Hoya Imperialis care routine just as a preventive.
TIPS TO KEEP HOYA IMPERIALIS PROBLEM-FREE
Growing Hoya Imperialis is all about striking a balance between too much and too little. Here are a few handy tips to keep the plant problem-free:
- Water it deeply but let it dry out between waterings.
- Grow Hoya Imperialis in a somewhat small pot that naturally limits the water available to the roots.
- Wash down your plant occasionally to keep it pest-free but do this only in the mornings.
- The soil mix should contain organic material like deadwood, bark, coconut husk, charcoal, along with draining material like perlite.
- Feed the plant additional orchid fertilizers for blooms.
- A bright spot and a lot of indirect sunlight is the best diet for blooms.
- Don’t expose it to cold drafts or direct sun.
- Don’t prune the flower peduncles. They will bloom again next year.
- The roots of this Hoya need some room to grow compared to other Hoyas that like it root-bound.
- If you want to repot, do it in May/June during growing months.
- In winters manage the humidity using humidifiers and cut down watering and feeding but don’t stop completely.
FREQUENTLY ASKED QUESTIONS ABOUT HOYA IMPERIALIS
Should I mist my Hoya Imperialis?
Misting with rainwater is an effective form of foliar feeding recommended in Hoya Imperialis care. Make sure you mist only in the mornings so that leaves have time to dry out, or they become susceptible to infections.
How old does Hoya Imperialis have to be before they bloom?
When grown from cuttings the plants is ready to bloom within 2 years from taking root. However, flowering is mostly a function of the right conditions and not necessarily age of the plant.
Does Hoya Imperialis grow and bloom under artificial light?
They have been observed to bloom under grow light kept on for about 12 hours a day. If you have low light issues this is your workaround.
How do you save an overwatered Hoya Imperialis?
CONCLUSION
If you’re here it’s safe to assume you’ve decided to add Hoyas to your home garden. Welcome to the club! The Bureau of Agricultural Research in the Philippines describes Hoya Imperialis as a “mangrove-loving plant”, one of a kind in the genus.
The plant clearly loves moisture and thrives in humid conditions but in a home environment, one must be mindful of rots and diseases as well.
Anyone who has a penchant for rare houseplants would find Hoyas a very rewarding experience.
If Imperialis is a rampant grower, then the vibrant Hoya genus offers specimens like Hoya Retusa that are delicate and slow-growing as well.
Once you’ve wrapped your head around the care guidelines for Hoya Imperialis, you can now add other exotic plants to your collection like Hoya Imbricata, Hoya Wayetii , Peperomias, etc.
Happy green thumbing!