Today's Gardener (todaysgardener.com) participates in the Amazon Services LLC Associates Program.
Hoya australis is one of the most popular species of the Hoya genus among plant lovers. What makes it unique are clusters of scented, star-shaped flowers, and a gorgeous central star sitting atop a larger one, thus resembling a cake ornament or a queen’s tiara. One can hardly resist its charm and beauty.
Brief overview: Growing and taking care of Hoya australis is not difficult if you know how to do it. Use a well-draining potting mix to plant it, keep it in bright to very bright indirect light, with moderate temperatures and humidity. Allow the soil surface to become quite dry between waterings. Propagate it from semi-ripe cuttings and be careful where you place the plant as a milky sap drips from the leaves. Make sure to inspect the plant for mealybugs and other insects.
What follows is a more elaborate guide on how to take proper care of Hoya australis. Here’s what we shall discuss:
- Introducing Hoya genus
- Essentials on Hoya australis
- Where can you grow Hoya australis?
- Light preferences of this plant
- What’s the best temperature?
- Does it need humid environment?
- How often do you need to water it?
- What are the soil requirements of this Hoya?
- Potting and repotting
- How to fertilize it properly?
- Is pruning complicated?
- Two types of propagation
- Pests, problems and diseases
- Why should you grow Hoya Australis?
- Care tips in a nutshell
Read on to find out all pieces of information that you need to that end!
Introducing Hoya genus
Hoya is the largest genus of Apocynaceae, a family of tropical trees, shrubs and vines that produce white latex. More specifically, Hoya falls into its apomorphic derivative or subfamily – the Asclepiadaceae, differently called the milkweed family.
The plant genus Hoya was named in honor of Thomas Hoy, a successful English gardener and botanist at Syon Park in England. It is a relatively large genus of around 350-450 species, most of which are epiphytic climbing or creeping tropical vines with waxy foliage, scramblers, danglers, and rarely trees or shrubs.
The distribution of Hoyas is in tropical and subtropical areas like Malesia, Borneo, New Guinea and the Philippines. Due to their popularity, they can also be found in many countries in Europe, Southeast Asia, the USA, Australia and tropical countries like Thailand.
Typical of these easily cultivated plants are their usually large leathery to succulent leaves with a shiny surface and flowers that form in umbels or clusters, giving some Hoyas an umbrella-like shape (Asclepias texana, for instance). Because Hoya plants have waxy leaves and flowers, they got the name wax plants.
Many species of Hoya are seen as favorite houseplants, grown for their luxuriant, evergreen foliage and fragrant flowers. During the evening and night, they produce a sweet scent that has a soothing effect. Apart from that, recent studies at the University of Georgia suggest that Hoya carnosa helps to purify the air.
Here are some common varieties of Hoya that are worth cultivating:
Unlike numerous exotic plants that must be treated with great care to grow healthy and look attractive, Hoya plants can get by very well with a certain amount of neglect. That’s why the interest in growing Hoyas as indoor plants is constantly increasing, especially as a hobby among busy people from all walks of life.
Essentials on Hoya australis
Hoya australis is an evergreen perennial succulent climbing vine native to tropical Australia. It is also known as wax plant, waxflower, porcelain flower and waxvine.
It comes in many different varieties. Some bear large, bold, hairless, glossy and waxy leaves like Hoya australis, while other varieties can be very thick, fuzzy and small-leafed, sparsely or densely hairy. Moreover, the leaves are either succulent, elliptical or oval. Some subspecies include:
- Hoya australis subsp. oramicola
- Hoya australis subsp. rupicola
- H. australis sanae
- H. australis tenuipes
Their flowers are always white, laying out flat or slightly cupped, with the majority having certain amounts of a carmine pink stain under the central star-shaped crown.
This particular species, Hoya australis, is the most commonly cultivated among other Australian subspecies and the most widely known after Hoya carnosa.
It can achieve a height of more than 3m. Though it is adapted to a wide range of environmental conditions, it is not as cold hardy as other subspecies like H. carnosa, nor will it tolerate excessive watering or very high humidity.
Nevertheless, it is not a fussy grower, so it is suitable for beginners and experts alike, and it will indubitably steal the show among your other plants.
Where Can You Grow Hoya Australis?
The wax plant can be grown outdoors if you live in tropical or subtropical areas and areas that are protected from frost. However, it is better to grow it as an indoor houseplant if you live in colder climates.
It is also suitable for growing in containers and hanging baskets since it is tolerant of root restraint. If not in a hanging basket, this vine could be trained on a trellis or as a wreath shape.
Immediately striking you in all its glory, Hoya australis takes on a special perspective if suspended in the air. In growing hanging plants, you will need a supporting structure strong enough to hold the plants and the container and a hanger, too. When selecting the location, take into account sunlight, shade and wind.
Some species like Hoya compacta look dazzling if hanging from the eaves of a wide walkaway or a balcony. You can give that a try with Hoya australis.
Another option is to hang them above an entry or porch to frame a door or a window and give your guests a pleasant welcome.
Should the temperatures drop, bring the plant inside, in which case it can be a jaw-dropping element in the kitchen or the dining room. It is bound to make the atmosphere tranquil and idyllic at the start of a busy day.
Light Preferences of This Plant
Light is the very essence of life for plants. If you want your waxvine to give you bursts of those fragrant, star-shaped flowers with burgundy centers, it needs bright indirect light. Ideally, let the plant soak up the early morning sun.
Avoid direct sunlight, since your plant can burn, get scorched or get undesirable spots. If exposed to more light than it needs, it can become yellowish-green in color.
In poor light (or God forbid full shade), the leaves can turn dark green, become weaker, leggy, and start falling off. Full shade also hinders the blooming process.
The leaves of a single plant are likely to get different hues of green if the plant doesn’t receive the proportionate amount of sunlight on all its sides. To prevent that from happening, you can rotate the plant occasionally.
Fluorescent tubes and artificial light will also encourage blooming in Hoya australis. A simple table or a shelf with some way of hanging lights fairly close to the plant is all you need.
If your fluorescent tubes are the only source of light, keep them on around 12 to 14 hours per day. However, make sure to provide a dark period as well. A timer can be useful to regulate the light and dark period. To mimic airflow, it is useful to have a blowing fan close to the lighting area, which will also prevent rust-colored spots.
Finally, make sure to observe the leaves of Hoya australis and make adjustments accordingly. They will let you know if your plant is happy or barely coping.
Related: 8 Best Grow Lights For Indoor Plants in 2021 : Reviews and Guide
What’s the Best Temperature?
Since Hoya australis is a tropical plant, it is no wonder that it likes warm environments.
Find a warm spot at a distance from the heating. Keep the room temperature at 18-24 degrees C and provide good airflow.
In the wintertime, when the temperatures drop and you don’t have a heating system inside your glasshouse, make sure to move your plant indoors.
Keep it away from windows and doors to protect it from draught. Make sure that the room temperature in the winter does not drop below 15 degrees C.
Does It Need Humid Environment?
In order to grow healthy Hoya australis, humidity is yet another important factor to be considered.
A moisture level between 40 and 60 % is preferable, so medium to slightly higher, which accelerates plant growth.
In addition, make sure that the air is not dry. To prevent that, you can mist your Hoyas with filtered or distilled add clean pebbles in a shallow tray filled with water and put the plant on top. You can also create a terrarium from a plastic bag. Finally, you can always opt for practical gadgets, such as a Levoit humidifier which is highly recommended.
How Often Do You Need to Water It?
It is common knowledge that succulent plants retain water inside their body. Since Hoya australis is a succulent vine, it likes to be it likes to be watered generously until the liquid runs through the holes on the bottom of the container. Allow the soil surface to become quite dry between waterings.
Avoid overwatering since it can cause the leaves to get yellow, fall off or lead to root rot. Ideally, you should use natural rainwater, which can also prevent root rot.
When it comes to seasonal care, keep the soil moist but not waterlogged in the summer, and water sparingly and infrequently in the colder months, only when the soil is completely dry.
If you are not sure if your plant needs a drink, you can check the moisture level using your fingers or a moisture meter. It is better, though, to irrigate it less frequent than too much.
Another trick is to observe the leaves to determine whether your plants are thirsty. If they are crinkly, they need more precious liquid. In case they are yellow and fall off, reduce it. If still in doubt, skip it.
Regarding misting, do it only if the plants are near the heating, except when the plant is in full bloom.
What Are the Soil Requirements of This Hoya?
Now that you have met the requirements for the process of photosynthesis – a sufficient amount of light, warm temperatures and the proper amount of humidity, let’s discuss soil requirements.
Well-aerated and well-draining potting mix is essential for growing healthy Hoya australis. You can buy a ready-made potting mix that contains peat moss, ground bark, sterilized manure, composted leaf mold, rice hulls and other additives. Check the ingredients on the bag and you can supplement those that are not on the list.
If you prefer making your own potting mix, you can always get these ingredients individually.
You can mix equal parts of peat-free compost, orchid bark and perlite which is a 100% neutral volcanic rock. Or you can use a succulent mixture or even your garden soil and add organic amendments- those I’ve already listed above.
Having combined the ingredients, the mixture should be sterilized in the oven (180 degrees for an hour in a covered container) and the pH of it should be mildly acidic to neutral (6.9 to 7.0). You can check the pH using a testing kit and if it isn’t neutral, you can add dolomite lime.
Whatever the case, make sure that the soil additives are wisely selected since they should loosen up the soil, aerate it, provide good drainage and prevent root rot.
Potting and Repotting
Choose a pot of appropriate size and appealing design, preferably with a 26 cm opening, because the porcelain flower doesn’t like being repotted frequently.
Don’t forget to check whether the pot has drainage holes to avoid clogging around the roots.
Be wary of overpotting! It is better to choose a larger pot and wait until the plant shows signs of being rootbound than to plant it in a small pot, whereupon you will have to repot it as soon as it outgrows the pot. Remember to replant only when absolutely necessary.
When repotting, make around 4 vertical slices around the root ball, remove all the old roots, repot with a fresh mix around this root mass and bury it just below the new soil line. Water thoroughly and place the plant in not so bright light for a week or so. Then you can slowly provide more light.
To summarize: Do not repot it too often, always use a sterilized medium and clean containers!
How to Fertilize it Properly?
First of all, keep in mind that fertilizers can never compensate for a poor environment, since they only provide additional nutrients, not the plant’s real food (like sugar which is produced through photosynthesis).
Nevertheless, you can treat your plants with a good fertilizer in the spring to summer, during the growing season to supplement the capacity of your soil for ideal growth and flower production.
The primary nutrients are nitrogen, phosphorus and potassium, while the secondary are calcium, magnesium and sulfur. You can use a higher nitrogen fertilizer to encourage foliage growth and switch to a phosphorous one once they start blooming.
The organic decomposition of peat moss and bark will also provide your plants with the necessary nutrients and so will natural rainwater.
Make sure not to fertilize excessively, but use fertilizers judiciously, in weak concentrations. Discontinue feeding in the winter since that’s the period of dormancy when the plants aren’t growing.
Related: Plant Fertilizing- Guide for Gardening Beginners
Is Pruning Complicated?
When the plant blossom, do not prune, pick or trim off the spur the flower came from, as it will flower in the same place again.
That means that if you prune off the spurs once the plant is done flowering, it won’t flower next time.
However, you can prune in the spring to maintain the desired height, but do not prune close to blooms or it will reduce new growth.
Two Types of Propagation
Hoya australis, like all Hoya plants, is easy to propagate from semi-ripe cuttings and there are two media to choose from – liquid medium (water) and solid medium (soil).
- Make cuttings of approximately 6″ long.
- Remove the foliage from one or two nodes. That’s because the roots will appear in nodal areas.
- Pour some water in a wider jar, use foil to cover it and pierce a couple of holes.
- Insert the cuttings through those holes so that they can reach the water below.
- Keep the container in an environment with adequate lighting and humidity levels
- To promote rooting, you can add a dust of rooting powder or vitamin B-1 solution.
- Maintain the temp at 72 degrees F.
- Sterilize the medium and the container. Speaking of the medium, you can use sponge rock, fine bark chips or loose potting soil.
- Make cuttings, but shorter than when you propagate in water.
- Place them on the soil horizontally and make sure to cover the nodes.
- Mist it regularly, but not excessively.
- Press the potting media tightly around the cutting.
Whatever the choice, place pots close together on a bed of gravel or other water-holding media to increase humidity. Remember which end is up and which one down, since the growing end does not like to be buried.
Given good conditions, roots will after a couple of days and the new growth in approximately 3 weeks. Refrain from constantly checking if the new growth or the roots have appeared and wait patiently.
Pests, Problems and Diseases
Given the proper environment and care, Hoya australis is mostly disease-free. Otherwise, there are some potential problems and five most frequent are:
- Insects like Aphids or mealybugs often pose a problem. Dab them with alcohol-soaked pads or use Malathion or Cygon outside the house.
- Snails, slugs and grasshoppers can also pose a problem. Get rid of them by placing diatomaceous earth around the pot or use metaldehyde-based baits and liquids.
- Red spiders and thrips can appear in dry conditions (low humidity).
- On the contrary, fungus diseases like Phomomis occur because of high humidity. Although this occurrence is rare, ensure good airflow to prevent this issue.
- Seedlings are subject to damp-off organisms, so use a systemic fungicide like Benomyl or copper-based fungicides.
In general, be ever watchful of the presence of these insects and use insecticidal sprays to protect your plant from the above-mentioned issues, but do remember that these sprays are poisonous, so move your plants to an outdoor area for treatment. Seek professional help should you fail to get rid of these issues.
Why Should You Grow Hoya Australis?
- The plant makes a memorable display, be it in your garden, home or office.
- It is an easy care and long lived plant with fragrant flowers
- Apocynaceae species are generally used to treat fever, malaria pain and diabetes. They are rich in metabolites, iridoids, alkaloids and cardenolides, which have a wide range of biological and pharmacological activities and anti-inflammatory properties. Others purify the air and timber species are also cultivated as ornamentals.
Care Tips in a Nutshell
- Protect the furniture from a milky sap and keep the plant away from children and animals to avoid irritation and allergic reactions.
- Ensure bright indirect light, a warm and humid environment. Avoid direct sunlight.
- Reduce watering and fertilizing in the period of dormancy.
- Increase watering and sunlight in the growing season, but do not prune the old spurs.
- In case you are using artificial light, make sure to keep a small fan blowing close to your lighting area to prevent red or rust-colored spots on the foliage.
Having Hoya australis is like having a precious relic. The breathtaking beauty of it is definitely worth putting effort into cultivating it as an indoor houseplant. The tips provided will help you do it.
Which Hoya Australis propagation method works better for you, in liquid or in solid medium? Share your precious experience with me and the readers, I can’t wait to hear from you!