The Hoya australis is a fairly popular variety with a few subspecies. It only comes second to the Hoya Carnosa in terms of popularity.
Like many hoya plants, this is a climbing vine that grows in tropical rainforest environments. It grows to between 12 to 34 feet in its native habitat. But, its size is a bit more manageable in containers, although still fairly long.
The plant is likewise known for its beautiful fragrant flowers that can be somewhat difficult to bloom. But when they do, they’re well worth it because of their stunning looks.
Another reason that many growers like hoyas is that they are fairly easy to care for. They are low maintenance so you don’t have to give them a lot to keep them happy.
However, there are 1 or 2 things that you need to know that avoid encountering problems later.
Hoya Australis Plant Care
Hoya Australis Light
The Hoya australis will do well in different lighting conditions. It won’t mind low light, artificial lighting all the way to bright light.
The one thing it cannot stand is long hours of direct sunlight. It also cannot tolerate hot, sunny conditions or the intense sunlight from the afternoon or peak of summer.
Given these conditions, its leaves will scorch and you’ll see them get bleached (pale in color).
However, for best growth, you want to give it lots of bright, indirect, filtered or dappled light. Partial sun is likewise good. The more light, the better as it increases its chances of blooming, provided that there it is not direct sunlight.
It won’t have a problem with 2 or 3 hours of direct morning sun. But, you don’t want to give it much more than that or place it where the sun’s rays can get very intense.
Don’t expect to see any flowers in low or medium light.
As such, in warm areas, an east facing window is the best.
If you live in cooler regions, the west and south facing windows will be better, especially as the months get cooler and there’s less natural light.
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Hoya Australis Temperature
Hoya australis enjoy temperatures that are similar to what you and I do. This runs from about 65 degrees to 80 degrees or so. It can likewise tolerate warmer weather as it comes from the tropical countries in Southeast Asia.
But, avoid temperatures lower than 60 degrees.
The plant is not frost hardy. Nor can it tolerate a lot of cold. If you live in USDA hardiness zones 10 and 11, then you can keep it outdoors all year round in sunny weather.
But, below zone 10, monitor the temperature as it gets close to 60 degrees. The plant can tolerate down to 55 degrees. But, you’ll want to observe it closely to see how it does there.
Depending on other conditions it may or may not do okay there. But, in no circumstance should you let it stay in the low 50s or below.
Finally, keep in mind that there are quite a few Hoya australis varieties. Those that live in higher elevation enjoy cooler nighttime temperatures. So, they can tolerate lower temperatures.
Hoya Australis Humidity
Your Hoya australis’ native habitat is the tropical forests of Southeast Asia. This means that it thrives in humid environments.
Indoors, it grows best when provided with these conditions, ideally over 60% relative humidity.
The good news is, it can tolerate lower humidity.
I have a few hoyas here at home in Southern California, which is a fairly dry place because of all the lack of rainfall. However, none of my hoyas have any problems with regular room temperature or humidity.
You do want to either mist or give it a shower every now and then.
I don’t like misting because it takes up a lot of time. When you have quite a few plants and need to mist twice or more a week, that adds up week in and week out.
So, I just give the hoyas a shower with a hose by the side of my house where I have a large washing areas (which is looks similar to those showers you see near the beach or in public pools). This makes it easy to water them.
Make sure to let them stay under the sun a bit to dry quickly since you don’t want to leave its foliage wet.
That said, you can likewise group your plants or place it over stones in a water tray to increase humidity.
Hoya Australis Watering
Unlike most houseplants, you want to keep your Hoya australis on the slightly dry side. Most houseplants prefer moist soil. But, that’s a bit wet for hoyas who are epiphytic.
As such, they prefer that moisture be fast drying. That’s because their roots receive a lot of air circulation which helps them dry faster.
Needless to say, soggy or muddy soil and overwatering is out of the question. Keeping it inn this condition will increase its risk of root rot. You never want to go there because it can destroy your plant.
As such, deep watering is the way to go with you Hoya australis. This means soaking the plant’s soil.
I like to run a hose on the soil and allow the water to keep going until you see it drip through the bottom drainage holes.
Then, leave the plant in the sink or similar place to completely drain. You want to wait until all the excess moisture from your watering drips out. This takes between 5 minutes (for smaller pots) to over 10 minutes (for bigger ones).
Once it is done, you can place it back to its spot.
The reason is it okay to allow the plant to go slightly dry is because in addition to being epiphytic, it has fleshy leaves like succulents. So, this allows it to store moisture and be drought tolerant.
Thus, keeping it in moist soil will increase the odds of overwatering.
In fact, I noticed that if I water more than once very 8 or so days in the summer it starts to whine. In the colder months once every 2 or 3 weeks is enough.
Again, I live in Southern California where the weather is fairly wamr compared to the rest of the country. So, do adjust accordingly.
don’t worry; the leaves will get back to their original form after a good watering session.
The majority of the cultivars grow epiphytically; therefore, Hoya australis prefers a drier root environment. It can tolerate a few weeks of drought but is usually sensitive to frost and cold weather.
From above, you already can guess what kind of soil your Hoya australis likes.
Because of its semi-succulent and epiphytic nature, it does best with loose, well-aerated, well-draining soil.
The loose and airy soil will allow oxygen and water to easily access its roots, much like how epiphytes get their sustenance in thee forest as they cling onto larger trees.
Its ability to be drought tolerant, store water and not like its feet wet means it prefers fast draining soil as well.
Slightly acidic to neutral soil with pH between 6.1 to 7.5 helps with optimum growth as well.
This means you have a few options you can go with.
If you prefer getting a commercial mix that’s out of the box from stores, choose either:
- Cactus or succulent mix
- Orchid soil
If you prefer making your own potting soil, you can use a combination of:
- 2 parts peat moss and 1 part perlite
- Regular soil and add perlite (add orchid bark to improve drainage if needed)
One thing you don’t want to use is sand. While sand will improve drainage, it tends to get compacted as time passes. This prevents the substrate from being airy enough. And, it makes it harder for oxygen and water to penetrate.
Hoya australis are light feeders. So, like water, it is always better to stay on the conservative rather than the aggressive side when it comes to feeding.
Here, you have a few options again.
If you have rich soil or use enough compost, you actually won’t need to add fertilizer. But, when doing so, observe how the plant behaves. Then adjust if needed.
In general, fertilizer is optional with this plant. But, it won’t grow optimally without it unless you use compost and add a layer of it at least once a year.
When going with traditional fertilizer, you want to likewise use a two-pronged approach. One is for the growing season, another for when the plant is blooming.
- Use a balanced fertilizer (15-15-15 will do) during spring and summer to help the plant grow at its best. Applying this once a month is more than enough. And make sure to dilute it. You can use a quarter teaspoon for every gallon of water.
- When it starts to bloom, switch to a 7-9-5 product. This will cut back on nitrogen which focuses on vegetative (foliage) growth. And, put more emphasis on flowering the more phosphorus.
Don’t fertilize during winter.
Flowering or blooming takes up a special section for hoyas because of their beautiful flowers.
Keep in mind that these flowers, albeit stunning and unique-looking are not a guarantee.
A lot will depend on its living conditions. And, even then, your location will also affect it.
In any case, it is always worth the extra effort because it fragrant blooms are amazing when they come out.
Like other hoyas, the flowers grow in clusters up to about 3 inches wide or so. And, are red-violet in color.
But, you do need patience, as they’ll often only bloom after their 2nd or 3rd year. Additionally, you want to give them as much sunlight as possible (indirect).
Keeping it is a slightly tight container also helps as its roots like being packed together.
Hoya Australis Pruning
Hoya australis don’t need a lot of pruning.
Keep in mind that that is a long-living plant and over time it will grow longer (up to 12 to 15 feet or more). As such, you may need to trim is to limit its size overall.
But, you won’t need to do so very often.
The best time to prune is in the spring or summer.
In most cases, you’ll be getting rid of leggy stems, dead or damaged vines and leaves.
Also be careful with over trimming it. You want to keep the short stalks as flowers grown on them. And, once they do, they’re likely to rebloom next season from the same stalks.
So, allow the faded flowers to drop. Don’t deadhead them as cutting the stems will require them to grow again before they can produce more flowers.
Hoya Australis Propagation
The easiest way to propagate your Hoya australis is via stem cutting. While there are other methods, this is the most common because it is straightforward and works very well. Plus, it allows the plant to grow fairly quickly as well.
The best time to propagate is during spring and summer. You want ideal warm conditions which makes it easier for the plant to deal with the shock of being moved.
How to Propagate Hoya Australis through Stem Cuttings
- Choose a healthy stem. You want to choose one with at least 2 or more leaf nodes. These are where the tiny roots will start growing out of the stem. So, you need nodes to propagate.
- Use a sterilized pair of scissors or pruning shears and cut off a stem that’s about 6 inches long.
- Place it in a glass or jar of water. Make sure to remove the leaves that will go underwater.
- Replace the water every few days to keep it clean.
- After 10 to 15 days, you should start seeing small roots come out from the stem.
- Wait until the roots get to about over an inch. Then move it to a potting soil.
- During the lull time, prepare a small pot and fresh well-draining potting soil. You can use a commercial mix or create your own as mentioned in the soil section above.
- After transferring the stem cutting, water when the medium is almost dry. Also, keep the plant in a warm, humid location with lots of bright light (no direct sunlight).
Transplanting & Repotting Hoya Australis
Repotting is another low maintenance job with your Hoya australis. In most cases you’ll only need to repot once every 2 or more years depending on how quickly it grows.
Most likely, you’ll be on the tail end of that range or even go past 4 years.
That’s because it likes being root bound. This actually helps it flower. So, most growers won’t move the plant unless it is absolutely necessary to do so.
This often means one of a few things. But all of them bordering on the plant having a hard time because the container has just gotten too small or too tight. These include:
- Roots clogging up the drainage holes
- Soil drying up very quickly soon after watering
- Signs of stress and difficulty growing
When repotting, spring and summer are the best times to do so.
And, you want to move it to a pot that’s one size bigger. This allows it to stay in a fitting container that isn’t too big.
Additionally, make sure you use well-draining potting mix and have at least a drainage hole in the bottom of the pot.
Unlike some other hoyas, the Australis is not pet-safe. Instead, it is toxic to humans as animals because it contains latex. So, keep young children, dogs, cats and horses away from it.
Pests and Diseases
Your Hoya australis is susceptible to pests. The most common of which are mealybugs.
In fact, mealybugs are the one thing you want to watch out for when growing any hoya plant.
In addition to mealybugs, you also want to be on the lookout for whiteflies, spider mites and aphids. All of which are bothersome and problematic as they will destroy your plant’s leaves and stems while draining if of its sustenance as well.
So, catching them early and treating them as quickly as possible is the best way to keep your plants healthy.
Horticultural oils and insecticidal soap are the best ways to deal with infestations.
As for diseases, water is the Hoya australis’ arch enemy. Allowing soil to stay moist or letting the plant sit in water will lead to root diseases. These are difficult to fix because you can’t see them. So, there’s often a good amount of damage by the time the symptoms reach the stem and leaves.
Thus, prevention (by staying on the dry side of things) is best.