Hoyas, popular for several generations, are adored by plant lovers and collectors, who nickname them “porcelain flowers” or “wax flowers” for the waxy appearance of their unique flowers. They are typically grown as climbing or trailing houseplants and blend well with all types of decor. Easy to maintain, hoyas tolerate the climate of our homes well and make magnificent decorative plants.
History & origins
Natural environment
Recognizing hoyas
Maintenance & advice
Watering
Pruning
Potting soil
Potting
Bloom
Temperature & humidity
Fertilizer
Lighting
Toxicity
Species
History & origins
Hoyas were introduced to the world of ornamental horticulture by Scotsman Robert Brown in the late 1800s. He named this plant genus after one of his very good friends, Thomas Hoy, who was also the gardener of the Duke of Northumberland.
Today, hoyas are making a comeback and can be found all over the world. If conditions are right and the climate resembles that of their natural environment, they can survive outdoors. They are often found in Central America and South America, for example.
Natural environment
Most hoyas come from tropical regions of Southeast Asia, the Pacific Islands as well as Australia. We also find certain species in more mountainous regions, therefore colder and higher in altitude. On the other hand, generally speaking, most hoyas like warm and humid climates.
Over time, some species have been so hybridized for various aesthetic attributes that they have lost characteristics that allowed them to survive in the wild. They need controlled conditions and do not like changes in their environment.
In the wild, 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 do not represent a family of plants, but rather a genus that belongs to the Apocynaceae family. To be more specific, hoyas belong to the subfamily Asclepiadaceae .
Here are some criteria that allow them to be recognized:
- They always have flowers with five petals;
- They have a sap which allows them to facilitate healing in the event of an injury;
- Their flowers are always in umbels.
We also notice differences in the fruit of 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"), like most plants belonging to the Asclepiadaceae subfamily. The majority of hoyas produce leaves that emerge in pairs but there are a few exceptions, such as Hoya imbricata . The nodes found on the stems can produce adventitious roots as well as inflorescences. Hoyas also tend to have long stems, which seek to twist around to hold on, before producing their leaves.
Inflorescence
Hoyas produce peduncles from which flowers emerge. These peduncles can flower repeatedly and will become longer with each flowering. Composed of 1 to 30 flowers, hoya inflorescences are also nicknamed “porcelain flowers” or “wax flowers” because of their unique appearance and texture.
Maintenance & advice: understand 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 will prefer more subdued light. The smaller the leaves, the more light the plants will need and, vice versa, the larger the leaves, the more the plant will prefer soft light.
Small leaves:
Small-leaved hoyas generally need more sun since the smaller surface area of their leaves impacts 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. Big leaf hoyas generally come from less light environments, and are forced to adapt to these conditions to survive. These hoyas are often found hidden among other plants, which serve as their guardians, in nature.
Example: Hoya glabra
Variegated leaves:
Generally speaking, hoyas with variegated leaves need more light because of the discolored parts which 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, like 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 significantly more ambient humidity. They often come from places in the world, like rainforests, where they never needed to evolve to store water.
Example: Hoya cembra
Succulent Leaves:
Hoyas with succulent or fleshy leaves have adapted to store more water in their leaves. They usually come from a drier environment and therefore require more spaced watering.
Example: Hoya kerrii splash
Providing Adequate Watering for Hoyas
When watering, you must wait until the top of the soil is dry before completely watering the entire soil. It is normal for your plants to require a little more water during flowering and the active growing period.
As explained above, it is important to keep in mind that the thinner the leaves, the closer together the watering will be. We advise you to water downy hoyas to avoid keeping too much moisture in the leaves and risking them rotting.
Is it necessary to prune my hoya?
It is preferable not to prune hoyas radically following flowering to avoid cutting peduncles which could 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 could affect the growth of your plant. If these stems are constantly growing and not producing leaves, you can pinch off the ends so they will start producing them more quickly. If after some time you notice that the stems continue to grow without making leaves, it is possible to cut them in order to obtain a more compact plant. The stems of hoyas usually try to cling, so until they find somewhere to wrap around, they may continue to grow without producing leaves.
Choosing the right potting soil for hoyas
If you were to visit a tropical rainforest, you would find that the soil there is mostly composed of leaves fallen from trees, rotting wood and compost, as well as charcoal left behind from forest fires in the over time. By taking the time to provide soil adapted to the specific needs of your hoyas, you will benefit from exceptional growth by providing them with an environment close to their natural habitat.
If you want to keep it simple, we recommend using our homemade hoya potting soil which has been formulated by our specialists to meet the specific needs of this type of plant. Otherwise, it is also possible to create your own mixture by combining a variety of substrates and thus creating a potting soil that offers everything the plant needs while remaining light, airy and offering excellent drainage.
To start, we advise you to use a mixture of around 20% high porosity potting soil to which you will add 20% coconut fiber and 20%black pine bark . Then you can add about 10% New Zealand sphagnum moss , 10% perlite , and 10% pumice . Optionally, it is possible to add 10% activated carbon to help control humidity and temperature variations and to avoid the risk of fungal diseases.
Substrates such as coconut fiber and black pine bark help retain moisture by releasing it slowly, without soaking the potting soil. Pine bark eventually decomposes, creating organic matter that will help enrich the soil. Other elements such as perlite, pumice and charcoal will add aeration to the mixture and help the roots grow healthily without the risk of mold. Sphagnum moss will help rehydrate the soil more easily.
Potting hoyas
The best time to repot your hoya is in early spring when the plant is preparing to enter a period of active growth (usually spring to mid-summer). If you need to repot at another time in the year, don't worry. Normally this will not cause a problem and it is just possible that your hoyas will recover a little more slowly. When repotting your hoya, be sure not to increase the size of the pot 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 offering diverse foliage, but the beauty of these plants does not stop there. Hoyas are also known for their unique flowers which are nicknamed “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 flavors such as cinnamon, vanilla, chocolate, citrus, popcorn and much more.
The flowers, as well as the leaves and stems of certain 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 male as well as female parts. They are also actinomorphic, meaning that the parts of a flower are arranged symmetrically about its center. The petals are welded to form a corolla to which the corona, made up of the pistil, is welded, thus forming a sort of crown.
The pollen is grouped together in the form of small balls called pollinia. It is quite complicated to pollinate flowers since each species has evolved its inflorescence to correspond to a certain type of insect. Thus, hoyas maximize their chances of pollination and survival, since there is no risk of contamination with pollen from other plants.
Hoyas are mainly pollinated by nocturnal insects. This is why their scent is generally stronger in the evening. The heat of their environment is also a factor that influences the intensity of the odor. Sometimes hoya flowers secrete a sweet nectar that drips over the flower to attract pollinators. The quantity of nectar is never the same, and it sometimes happens that some hoyas produce such a quantity that the owner of the plant must protect the flowers, to prevent the nectar from spreading everywhere, and attracting harmful insects .
Maintain a temperature and humidity that favors the growth of hoyas
Since there are several species of hoyas from a multitude of varied environments around the world, it is important to know the species of hoyas in your collection and thus be able to offer them an environment adapted to their specific needs.
The ideal humidity for the majority of hoyas should be kept above 40%, preferably in the region of 60% and above. If the humidity in your home is too low, you can install small humidifiers or plates with clay balls covered in water to help maintain adequate ambient humidity.
Different species of hoyas also have different temperature needs. For hoyas that come from more mountainous environments, and therefore prefer cooler temperatures, they will need to be acclimatized to an environment ranging from 10 to 25 °C . For hoya varieties from warmer climates, it will be important to place them in a location that reaches at least 21 °C .
Generally speaking, most hoya species live well in temperatures that do not fall below 15 °C and do not exceed 35 °C .
Fertilizers and fertilization of hoyas
During their growth period, you will need to give your hoya liquid fertilizer (frequency: every other watering). Preferably choose a fertilizer rich in potassium (such as seaweed or stimyla ). In spring, you can occasionally add a fertilizer richer in phosphorus to encourage the appearance of flowers. Hoyas also appreciate foliar fertilization, but it is absolutely necessary to have good ventilation to avoid fungal problems. The ideal is to spray the underside of the leaves with a small drop spray like a mister.
The lighting necessary for the development of hoyas
As with most tropical plants, hoyas do not go through true dormancy. However, when temperatures drop and are accompanied by dark days with very little light, hoyas slow their growth drastically and show no apparent activity until conditions improve. Plants grown under artificial lights and uniform temperatures will continue to grow and even flower in all seasons.
Generally speaking, the absolute minimum for hoya growth is twelve to fourteen hours of light per day. If you want to make your hoyas 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 photosynthesis and use the energy produced during the day.
Some hoyas can tolerate excess bright light. This intense light will cause them a certain stress and they will develop interesting colors, to the delight of lovers of these plants (for example: Hoya sunrise , Hoya sp.gunung gading , Hoya pachyclada new moon ). The so-called “splash” characters can also develop further with excess light. Hoya variegata will tend to prefer a brighter exposure since they produce less chlorophyll for their photosynthesis. This will allow them to develop more vibrant colors. On the other hand, be careful of sunburn. It is always important to properly acclimatize your plants to the new lighting, which should be offered gradually.
Are hoyas poisonous?
While several 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 the health of humans and animals.
Our favorite hoya species
Hoya imbricata
Hoya imbricata is found almost everywhere throughout the tropical zones of Asia. It produces a single leaf per node, which produces a dome shape attaching to tree trunks or other surfaces. These leaves can measure from 2 inches to 10 inches in diameter. In nature, 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 is said to have been seen more recently 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 loses as it matures. When a new leaf develops, it is burgundy in color before turning green. It is a hoya that changes colors a lot, its final color only stabilizing after a few months.
Varieties: Hoya caudata "Sumatra" , Hoya caudata gold and Hoya caudata splash & silver
Hoya archboldiana
Hoya archboldiana is named in honor of 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 that can reach up to two inches in diameter.
Varieties: Hoya archboldiana white , Hoya archboldiana red
Hoya finlaysonii
Originally from Penang in Malaysia, Hoya finlaysonii is named in honor of one of the collectors who discovered it. Its leaves are particularly thick and hard and its flowers give off a slight scent of cinnamon. This hoya, rather easy to maintain, offers medium to rapid growth 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
Hoya gunung gading , which translates to "Ivory Mountain", is part of the Finlaysonii type. It was discovered in Gunung Gading National Park in the Sarawak region of the island of Borneo. It is a very popular hoya with collectors since it can display colors ranging from red to very bright orange, with strong exposure to the sun.
Hoya curtisii
Native to southeast 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 it is sensitive to variations in its environment. Hoya curtisii likes temperatures above 15 C° as well as lots of ambient humidity.
Hoya carnosa
Hoya carnosa is the classic hoya with pink flowers. This is one of the easiest varieties to grow; she is the mother of several hybrids highly appreciated by collectors. This type of hoya is perfect for beginners since it does not require a lot of ambient humidity or intense sun.
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 , meaning “the most beautiful leaves”. As its name suggests, its foliage decorated with veins is magnificent. This hoya has evolved to retain water in its leathery leaves. Its flowers are red and yellow with a cream center.
Hoya pubicalyx
Hoya pubicalyx is a very easy species to grow and is a perfect choice for beginners. Its flowers can vary from black to white, pink and purple depending on the hybrid. It offers one of the fastest growing 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. Its growth is slow compared to other large-leaved hoyas and it requires a lot of light to encourage it.
Varieties: Hoya kerrii “Splash ” , Hoya kerrii variegata
