Hoya plants – also called wax flowers or porcelain flowers – are popular because of their beautiful flowers and ornamental leaves. Here we will introduce you to some waxplant species and give you our top tips on growing and caring for them.
The waxflower is an evergreen houseplant. It forms small, star-shaped flowers with a distinctive wax-like shimmer which come in different colours depending on the species.
- Hoya: flower, characteristics, and origin
- The most beautiful hoya types
- Planting wax plants
- Hoya care
- Propagate hoya from cuttings and offshoots
- Overwintering wax flowers
- Is the hoya plant poisonous?
Hoya: flower, characteristics, and origin
Hoya, also known as the wax flower or porcelain flower, is a genus belonging to the subfamily Asclepiadoideae, in the family Apocynaceae. Hoya plants are found widespread in nature from Asia to Oceania. The evergreen houseplants grow partly in the ground and partly epiphytically (perched on other plants). Wax flowers are not parasites, however, but take root in old, already decaying bark. The plants form aerial roots, have very low nutrient requirements, and are good at storing water. They prefer high humidity because they would otherwise dry out quickly.
Hoya is an herbaceous plant that only becomes slightly woody and is often grown on round arches because of its flexibility. The plant grows vigorously, and its shoots can grow several metres long. Some species grow like vines, others more like shrubs. Because of their overhanging growth, they are ideal for hanging baskets. Some species have a climbing growth with adventitious roots (plant roots are formed from any non-root tissue).
Hoya plants flower between spring and autumn. Lots of individual flowers of about 1.5cm in size form large flower clusters. The individual flowers are star-shaped and, depending on the species and variety, pale pink, white, purple, or pale yellow in colour. The petals have a double structure: On the outside there are five fused petals, and inside there is another row of five fused, smaller petals. The second row of petals are often a different colour to the outer. In the very centre are the sexual organs of the flowers. The flowers of most species produce a sweet fragrance, secrete nectar, and have a waxy sheen. With their distinctive flower structure, hoyas belong to the group of pinch-trap flowers, which have an unusual pollination system. The waxy flowers use pollinia (sticky masses of pollen) to trap flower-visiting insects. When the insects free themselves from the “grip” of the flowers, they often tear the pollinia with them and carry it on to the next flower.
The leaves are about 5 to 8cm long, slightly oval-shaped and pointed. They are dark green in colour, succulent (thickened to store water) and usually have a waxy, shiny surface.
The most beautiful hoya types
The genus Hoya is made up of more than 300 species of porcelain flowers. Here you will find a brief overview of the most popular species:
Hoya carnosa is very easy to care for and is probably one of the most common waxflower species. It displays a fast, climbing growth and its leaves are usually dark green and glossy. However, there are also varieties with white variegated and twisted or wavy leaves. The flowers of this hoya plant have porcelain white or pink petals with a dark red centre.
Hoya bella is a small, compact wax flower that has a branching growth. Its leaves are grey-green in colour and have a matt shine. The flower clusters are made up of white, star-shaped flowers with dark red centres.
Hoya multiflora is distinguishable from other hoya plants by the shape of its flowers. The individual flowers are pointed to the sides like arrowheads. They are also larger and have one ring of white and one ring of yellow petals. The dark green leaves of Hoya multiflora are thin, oval, and slightly wavy.
Hoya imperialis has distinctive wavy leaves. The most striking feature of this species, however, is the size of the slightly forward-curved flowers. The individual pink-violet flowers are about 5cm in size and have a waxy sheen. The petals in the centre are white.
Hoya kerrii, also called heart leaf or sweetheart hoya, is another particularly popular species. It stands out because of the beautiful heart-shaped form of its leaves. The flowers in most of its varieties are white.
Planting wax plants
Once you have found the right hoya plant for you and are ready to plant it, you will need to choose a suitable pot, soil, and location.
The right location and soil for hoya
First things first, each hoya species has its own individual needs. However, we have outlined a few of their common features here.
To give your hoya plant the right conditions for healthy growth, place it in a sheltered, bright, and warm spot in your home. A windowsill, for example, works well for this, although you should avoid direct sunlight. This is down to the fact that in their natural habitat, wax flowers are found under the leaves of the trees on which they grow. Some hoya plants even prefer to grow in shade. Avoid draughts too. Wax flowers also enjoy high humidity, so spray the plants with a little low-lime water every so often.
The ideal room temperature is 18 to 25°C, depending on the species. During the winter months, the wax flower goes into a kind of hibernation, so place the plant in a cooler spot with temperatures between 10 and 15°C. This promotes flower formation.
When it comes to soil, hoya plants need good root aeration and drainage for healthy development. As epiphytes, most species of hoyas are used to having their roots well aerated. Unfortunately, there is no such thing as specially adapted “hoya soil” – so you will need to mix your own. Use a peat-free potting soil such as our Plantura Organic All Purpose Compost as a basis. To prevent the compost from compacting and to reduce the nutrient content, mix it with 30% expanded clay and 30% pine bark or orchid soil. This gives the soil better structure, while lowering the nutrient density and the pH value – perfect conditions for healthy hoya roots.
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How to plant hoya
Choose a pot with a drainage hole, as hoya plants are sensitive to waterlogging. If the roots are permanently wet, soil-borne pathogens quickly gather, which manifests in root rot. Remove the wax flower from its container and place it in the centre of the new pot. Now fill it up with your soil mix and press down.
Recap: planting wax flower
- Location: a sheltered, bright, and warm place without direct sunlight
- Room temperature: 18-25°C
- Soil: mixture of potting soil (such as Plantura Organic All Purpose Compost), expanded clay, and pine bark/orchid soil
- Choose a pot with a drainage hole
Generally, wax flowers are low maintenance houseplants. Apart from regular watering, occasional fertilising, and repotting when the pot is fully rooted, there are usually no further care steps.
Water your porcelain flowers little and often during the growing season from March to October. After watering, wait until the soil has dried out before watering again. In winter, wax flowers need less frequent watering and smaller amounts of water. The latter is especially important if the soil is not permeable enough. This is the case, for example, if normal potting soil has been used.
The same applies to fertilising the waxflower as to watering. During the growing season, fertiliser should be applied every three to four weeks. A liquid green plant food such as our Plantura Liquid Houseplant Food is ideal. This is applied with the water and provides your green plants with all the essential nutrients. Apply a dosage of 15 to 25ml per 5 litres of water. The porcelain flower does not need fertiliser in winter.
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Porcelain flowers do not only grow above ground, but their root system also spreads underground. Repot your wax flower as soon as it outgrows the pot. Choose a new pot just a few centimetres larger than the old one. Do this between February and March. Older wax flowers in particular are negatively affected by repotting, which results in reduced formation of new flower buds. So, try not to do this too often. When repotting, it is a good idea to prune – spring is also the best time for this.
How to prune hoya
Only prune wax flowers when their growth becomes too spreading. New buds usually form again and again on the old flower shoots, so it would be a shame to remove them prematurely. If you still want to cut your porcelain flower because it is getting too big or is not growing in the shape you want, cut with scissors or a knife above a leaf axil so that the hoya plant can form a new sprout at this point.
Hoya plant not flowering: what to do?
Wax flowers react to different conditions by reducing flower formation or even stopping it all together. If this is the case, the cause may be excess nutrients, so use less fertiliser. Another reason for a lack of flowering can be that the winter temperatures are too high: Make sure to place the hoya in a cool spot during the winter period. You should also avoid pruning the porcelain flower, if possible, as it also forms new flower buds on old flower shoots. Last but not least, the wax flower should not be moved or turned once in the right location. Porcelain flowers usually set their flowers on the side facing the light. If you turn the plant before the flowers open, the buds may fall off.
Propagate hoya from cuttings and offshoots
Wax flowers can be propagated vegetatively in two ways: from cuttings and from offshoots. Propagation by cuttings works as follows: In spring, cut off approximately 10cm, only slightly woody shoot tips and shoot parts from the wax flower. Then put into pots filled with a moist, loose, and nutrient-poor soil in a bright spot without direct sunlight, for example on a windowsill. Our Plantura Organic Herb & Seedling Compost would be an ideal soil for cuttings. To make it even looser, add some sand, perlite or crushed expanded clay. At temperatures between 20 and 25°C and with regular watering, the cuttings will take root within two to three months.
Alternatively, the hoya plant can also be easily propagated from offshoots. To do this, fill a pot with the above-mentioned soil mixture and lower a shoot of the mother plant into it. This means that you carefully bend down a tendril and place it on the soil. At the point where the shoot makes contact with the soil, remove the leaves and secure the vine in place with a peg. Then shorten the tip of the shoot slightly. As with propagation from cuttings, it takes some time for roots to form. After this has happened and the shoot sprouts anew, the propagation has been successful, and the cloned plant can be cut off from the mother plant.
As well as the vegetative propagation methods above, generative propagation from seed is also possible.
Pollination is only carried out by specific insects – but you can assist in this process by using a brush to go from flower to flower and from plant to plant. Seed pods form, which eventually burst open. To prevent the seeds from being thrown far from the plant, wrap the pods in a fine net beforehand.
The seeds can germinate for up to one month, so do not wait too long before sowing them. Spread the hoya seeds on a suitable soil mixture, but do not cover with soil as they are light germinators. Keep the soil moist. Cover the pots with plastic or foil to increase the humidity and prevent draughts. Place the seed pots in a warm place, around 20°C. Generally, the seeds germinate within a few days and quickly grow into small hoya plants. However, the speed of growth and development depends very much on the species.
Overwintering wax flowers
Wax flowers do not tolerate cold. Therefore, after flowering, it is best to place your wax flower in a bright spot in your home or conservatory. Ideally, the temperature should be between 10 and 15°C or a maximum of 20°C. If warmer than this, the plant will form long, flowerless winter shoots. Furthermore, do not expose the houseplant to strong temperature changes or draughts. During the winter months, water the waxflower little and infrequently. There is no need to fertilise during this time.
Is the hoya plant poisonous?
Wax flowers are poisonous. Some hoya species are even considered highly poisonous in exceptional cases. Hoyas contain cardiac glycosides that are potentially life-threatening. However, because of the unpleasant taste, there have been no known cases of poisoning. Small amounts cause vomiting, which protects us from a life-threatening dose.
Hoya carnosa can also trigger an allergic response. Allergy symptoms occur when susceptible people are in regular contact with the plants (for example, when pruning, watering, and repotting). Symptoms include, for example, rhinitis, eye redness, coughing, and asthma. In these cases, the allergen reaches the respiratory tract through the air. Other symptoms such as skin redness and eczema occur as a reaction to skin contact. If you experience these symptoms, consult a doctor and mention that you have wax flowers in the house. Whether the plant is the trigger can be checked with a blood test. If this proves to be the case, remove the plant from the house.
If you are interested in discovering more low-maintenance plants for your home, read our article on easy-care houseplants.