Caring for Hoyas

Hoyas have been popular for generations and are loved by plant lovers and collectors, who call them 'porcelain flowers' or 'wax flowers' for the waxy appearance of their unique blooms. They are usually grown as climbing or drooping houseplants and blend well with all types of décor. Easy to care for, hoyas tolerate our home climate well and make beautiful decorative plants.

History & origins
Natural environment
Recognising hoyas
Plant Care & Advice
Watering
Pruning
Potting soil
Potting
Flowering
Temperature & humidity
Fertilizers
Lighting
Toxicity
Species

History & origins

Hoyas were introduced to the world of ornamental horticulture by the Scotsman Robert Brown in the late 1800's. He named this type of plant after a very good friend of his, Thomas Hoy, who was also the Duke of Northumberland's gardener.

Today, hoyas are making a comeback and can be found all over the world. If the conditions are right and the climate is similar to their natural environment, they can survive outdoors. They are often found in Central and South America, for example.

Natural environment

Most hoyas come from the tropical regions of South-East Asia, the Pacific Islands and Australia. Some species are also found in more mountainous regions, which are colder and higher in altitude. In general, however, most hoyas like warm and humid climates.

Over time, some species have become so hybridised for various aesthetic attributes that they have lost characteristics that allow them to survive in the wild. They need controlled conditions and do not appreciate changes in their environment.

In nature, most hoyas are epiphytic plants. This means that they cling to the bark of trees or rock faces in order to climb and reach the light exposure they need.

How to recognize hoyas

First of all, it is important to note that hoyas are not a plant family, but rather a genus that belongs to the family Apocynaceae. To be more precise, hoyas belong to the subfamily Asclepiadaceae.

Here are some criteria for recognising them:

• They always have five-petalled flowers;
• They have a sap that allows them to facilitate healing in case of injury;
• Their flowers are always in umbels.

There are also differences in the fruit of the Apocynaceae from that of other Asclepiadaceae. Their genetics also differ slightly.

Leaves and stems

The stems of hoyas contain a milky or clear sap (called 'milkweed' in English), as do most plants belonging to the subfamily Asclepiadaceae. Most hoyas produce leaves that emerge in pairs, but there are some exceptions, such as Hoya imbricata. The nodes found on the stems can produce adventitious roots as well as inflorescences. Hoyas also tend to make long stems, which seek to curl up to hold on, before producing their leaves.

Inflorescence

Hoyas produce peduncles from which the flowers emerge. These peduncles can flower several times and will become longer with each flowering. Composed of 1 to 30 flowers, the inflorescences of hoyas are also known as "porcelain flowers" or "wax flowers" because of their unique appearance and texture.

Plant Care & Advice: Understanding the Needs of Each Type of Hoya

To understand and master the care of your hoyas, it is important to be able to differentiate between the various types of leaves and their adaptation. This is often an excellent indicator of their native environment as well as their specific maintenance needs. Some hoyas require more bright light while other species prefer a more subdued light. The smaller the leaves, the more light the plants will need and, vice versa, the larger the leaves, the more soft light the plant will prefer.

Small leaves :

Small-leafed hoyas generally need more sunlight as the smaller leaf area affects their ability to absorb the light the plant needs. This type of hoya usually comes from sunnier locations.

Example: Hoya lacunosa splash

Large leaves :

This type of hoya has leaves that provide a larger surface area to absorb more light. Large-leafed hoyas usually come from less light environments, and are forced to adapt to these conditions in order to survive. These hoyas are often found hidden among other plants in the wild, which act as a support for them.

Example: Hoya glabra

variegated leaves :

In general, variegated hoyas need more light because of the discoloured parts that do not produce chlorophyll. Since chlorophyll is essential for photosynthesis, this means that the green parts of the leaves have to work harder to compensate for the lack caused by the white parts. These hoyas will also be more sensitive to excess water, as will other variegated plants.

Example: Hoya wayetii variegata

Thin sheets :

Like many other types of plants, thin-leaved hoyas generally need to be watered more often and require much more ambient humidity. They often come from places in the world, such as rainforests, where they have never needed to grow to store water.

Example: Hoya cembra

Succulent leaves :

Succulent or fleshy leafed hoyas have adapted to store more water in their leaves. They usually come from a drier environment and therefore require more frequent watering.

Example: Hoya kerrii splash

Provide adequate watering for hoyas

When watering, wait until the top of the soil is dry before watering the entire soil. It is normal for your plants to require a little more water during the flowering and active growth period.

As explained above, it is important to keep in mind that the thinner the leaves, the more often you will have to water them. We advise you to water the pubescent hoyas to avoid keeping too much moisture in the leaves and risking rotting.

Is it necessary to trim my hoya?

It is best not to prune hoyas drastically after flowering to avoid cutting off stalks that may re-flower several times in the same place. As mentioned above, hoyas tend to grow long stems before the leaves appear. It is therefore extremely important not to cut them too early, as this will affect the growth of your plant. If these stems grow continuously and do not produce leaves, you can pinch off the ends so that they start producing leaves more quickly. If after a while you notice that the stems continue to grow without making leaves, you can cut them back to make a more compact plant. The stems of hoyas are usually looking for a place to hang on, so until they find a place to curl up, they may continue to grow without producing leaves.

Choosing the right soil for hoyas

If you were to visit a tropical rainforest, you would find that the soil there is mainly composed of fallen leaves, decaying wood and compost, as well as charcoal left behind by forest fires over time. By taking the time to provide a potting soil adapted to the specific needs of your hoyas, you will benefit from exceptional growth by offering them an environment close to their natural habitat.

If you want to keep it simple, we recommend using our homemade hoyas potting soil which has been formulated by our specialists to meet the specific needs of this type of plant. Alternatively, you can create your own mix by combining a variety of substrates to create a potting soil that provides everything the plant needs while remaining light, airy and providing excellent drainage.

To start with, we recommend using a mixture of about 20% high porosity potting soil to which you add 20% coconut fibre and 20%black pine bark. Then you can add about 10% New Zealand Sphagnum moss, 10% perlite, and 10% pumice. Optionally, you can add 10% activated charcoal to help control humidity and temperature variations and avoid the risk of fungal diseases.

Substrates such as coconut fibre and black pine bark help retain moisture by releasing it slowly, without soaking the soil. The pine bark will eventually decompose, creating organic matter that will help enrich the soil. Other elements such as perlite, pumice and charcoal will add aeration to the mix and help the roots to grow healthily without the risk of mould. Sphagnum moss will help to rehydrate the soil more easily.

Potting of hoyas

The best time to repot your hoya is in early spring when the plant is getting ready to enter an active growth period (usually from spring to midsummer). If you have to repot at any other time of the year, don't worry. Normally this will not cause any problems and it is just possible that your hoyas will recover a little more slowly. When repotting your hoya, make sure you do not increase the size of the pot by more than 1 to 2 inches in diameter and always choose a pot with a drainage hole.

Flowering and pollination of hoyas

Not only are there a variety of hoya species with diverse foliage, but the beauty of these plants does not end there. Hoyas are also known for their unique flowers, which are known as 'porcelain flowers' or 'wax flowers'. Many hoyas produce highly aromatic flowers that are used in the fragrance market, such as perfumes and lotions. There is a wide variety of fragrances such as cinnamon, vanilla, chocolate, citrus, popcorn and many more.

The flowers, as well as the leaves and stems of some species, are covered with very small hairs or scales called trichomes. These are modified epidermal cells that allow the plant to dry more quickly to resist rot and fungal diseases. These trichomes also help protect the plant from certain insects.

The flowers are bisexual and have both male and female parts. They are also actinomorphic, which means that the parts of a flower are arranged symmetrically in relation to its centre. The petals are fused together to form a corolla to which the corona, consisting of the pistil, is fused, forming a kind of crown.

The pollen is collected in small balls called pollinia. It is quite complicated to pollinate the flowers as each species has evolved its inflorescence to match a certain type of insect. Thus, hoyas maximise their chances of pollination, and survival, as there is no risk of contamination with pollen from other plants.

Hoyas are mostly pollinated by nocturnal insects. This is why their scent is generally stronger in the evening. The warmth of the environment is also a factor that influences the intensity of the scent. Sometimes hoya flowers secrete a sweet nectar that flows over the flower to attract pollinators. The amount of nectar is never the same, and sometimes some hoyas produce so much nectar that the plant owner has to protect the flowers, to prevent the nectar from spreading everywhere, and attracting pests.

Maintain a temperature and humidity that promotes the growth of hoyas

Since there are many species of hoyas from a variety of environments around the world, it is important to be familiar with the species of hoyas in your collection so that you can provide them with an environment suited to their specific needs.

The ideal humidity for most hoyas should be kept above 40%, preferably around 60% and above. If the humidity in your home is too low, you can install small humidifiers or plates with water-covered clay balls to help maintain adequate humidity.

Different species of hoyas also have different temperature requirements. For hoyas that come from more mountainous environments, and therefore prefer cooler temperatures, they will need to be acclimatised to an environment ranging from 10 to 25 °C. For hoyas from warmer climates, it will be important to place them in an area that reaches at least 21°C.

In general, most species of hoyas live well in temperatures that do not fall below 15 °C and do not exceed 35 °C.

Fertilizing and fertilizing hoyas

During their growth period, your hoya should be given liquid fertiliser (every other watering). Preferably choose a fertiliser rich in potassium (such as seaweed or stimyla). In the spring, you can occasionally apply a fertiliser with a higher phosphorus content to encourage the development of flowers. Hoyas also appreciate foliar fertilisation, but good ventilation is absolutely necessary to avoid fungal problems. Ideally, the underside of the leaves should be sprayed with a misting sprayer.

The light needed for the development of hoyas

As with most tropical plants, hoyas do not go through a true dormancy. However, when temperatures drop and are accompanied by dark days with very little light, hoyas slow down their growth dramatically and show no apparent activity until conditions improve. Plants grown under artificial lights and with uniform temperatures will continue to grow and even flower in all seasons.

In general, the absolute minimum for growing hoyas is twelve to fourteen hours of light per day. If you want your hoyas to flower, they will need about sixteen hours of light. Remember that all plants need a period of darkness (at night) such as that provided in their natural habitat. Darkness allows the plant to stop photosynthesizing and use the energy produced during the day.

Some hoyas can tolerate too much bright light. This intense light will cause them some stress and they will develop interesting colours, for the pleasure of the lovers of these plants (for example : Hoya sunrise, Hoya sp.gunung gading, Hoya pachyclada new moon). Splashy characters can also develop more with excess light. Hoyas variegata will tend to prefer a brighter exposure as they produce less chlorophyll for photosynthesis. This will allow them to develop more vibrant colours. However, beware of sunburn. It is always important to acclimatise your plants to the new lighting, which should be offered gradually.

Are hoyas toxic?

While many of the plants in this family are more or less toxic, some research has been done on the toxicity of hoyas in particular. It has been determined that hoyas are plants that are considered non-harmful to human and animal health.

Our favourite hoya species

Hoya imbricata

Hoya imbricata is found throughout tropical Asia. It produces a single leaf per node, which produces a dome shape that attaches to tree trunks or other surfaces. These leaves can range from 2 inches to 10 inches in diameter. In the wild, ants use its leaves as a storage place for their food.

Varieties: Hoya imbricata and Hoya imbricata green

Hoya caudata

This famous plant can be found in Southern Thailand and Malaysia, and more recently has been seen on the island of Borneo. Hoya caudata is found on limestone hills in low, dense forests. When the plant is young, it is covered with several hairs (trichomes) which it sheds as it matures. When a new leaf develops, it is burgundy in colour before turning green. It is a hoya that changes colour a lot, its final colour only stabilising after a few months.

Varieties : Hoya caudata "Sumatra", Hoya caudata gold and Hoya caudata splash & silver

Hoya archboldiana

The Hoya archboldiana is named after the famous American aviator and explorer Richard Archbold. This species was first discovered in Papua New Guinea. It is a hoya that produces very large flowers up to two inches in diameter.

Varieties : Hoya archboldiana white, Hoya archboldiana red

Hoya finlaysonii

Native to Penang in Malaysia, Hoya finlaysonii is named after one of the collectors who discovered it. Its leaves are particularly thick and hard and its flowers have a slight cinnamon smell. This rather easy to care for hoya is medium to fast growing and prefers a temperature of over 21°C.

Varieties: Hoya finlaysonii sukirin, Hoya finlaysonii splash, Hoya finlaysonii panggha, Hoya finlaysonii big leaves, Hoya finlaysonii chicken farm, Hoya finlaysonii nova

Hoya gunung gading

The Hoya gunung gadingHoya gunung gading, which translates as 'Ivory Mountain', is of the Finlaysonii type. It was found in Gunung Gading National Park in the Sarawak region of Borneo. It is a very popular hoya with collectors as it can display colours ranging from red to very bright orange, with strong exposure to sunlight.

Hoya curtisii

Native to South East Asia, Hoya curtisii has developed small spotted leaves that can turn purple in the sun. It requires a lot of light to produce its white flowers and is sensitive to variations in its environment. Hoya curtisii likes temperatures above 15 C° and plenty of humidity.

Hoya carnosa

Hoya carnosa is the classic pink flowered hoya. It is one of the easiest varieties to grow and is the mother of several hybrids that are very popular with collectors. This type of hoya is perfect for beginners as it does not require a lot of ambient humidity or intense sunlight.

Varieties : Hoya carnosa krimson queen, Hoya carnosa krimson princess, Hoya carnosa compacta albomarginata

Hoya callistophylla

Its name comes from the Latin words kallisto and phylum, which mean 'the most beautiful leaves'. As the name suggests, its veined foliage is beautiful. This hoya has evolved to retain water in its tough leaves. Its flowers are red and yellow with a cream centre.

Hoya pubicalyx

Hoya pubicalyx is a very easy to grow species and is a perfect choice for beginners. Its flowers can vary from black to white to pink and purple depending on the hybrid. It is one of the fastest growing of the hoyas. 

Varieties : Hoya pubicalyx 'Black Dragon, Hoya pubicalyx "White Dragon, Hoya pubicalyx "Royal Hawaiian" purple

Hoya kerrii

Named by Dr. Arthur Francis George Kerr, Hoya kerrii is easy to recognize. Its heart-shaped leaves are leathery and waterlogged. It is slow growing compared to other large leafed hoyas and requires plenty of light to encourage growth.

Varieties : Hoya kerrii 'Splash" Hoya kerrii variegata