For the record: my love of houseplants was born during the pandemic. I started out by buying two small pots to make my office less austere, then quickly moved on to quantities that modesty prevents me from revealing here. I’m not the only one: during the COVID pandemic, many people turned to growing houseplants, and the catalog of available plants diversified. One of the families that has gained most in popularity is the waxplant or Hoya, which I’ll introduce in this article.
The genus Hoya refers to several plant species in the Apocynaceae family. Native to the tropical and subtropical climates of Asia and Oceania, members of this family can be found in a variety of environments, under a wide range of temperatures, altitudes and plant strata. Hoyas have therefore developed under a variety of conditions, giving rise to a particularly varied genus, much to the delight of collectors!
The plant was discovered and classified in the early 19th century. Although experiencing a resurgence in popularity, hoya has been cultivated as a houseplant for over 200 years (including Hoya carnosa, one of the most widespread species). Other plants in the Apocynaceae family are milkweeds and dischidias, which are also occasionally grown as houseplants.
Scottish botanist and paleobotanist Robert Brown named the genus in honor of his friend Thomas Hoy. Its common names are waxplant, waxvine or waxflower.
It’s difficult to paint a homogeneous picture of hoyas, since the family itself is spread over two continents with very different climates! Hoyas are evergreen plants. Their leaves come in a variety of shapes, generally elliptical, but also round, linear or heart-shaped. Many are smooth, some are covered with silver spots or small hairs, and others are distinguished by very visible veins, even of a different color.
In the Wild
In the wild, most hoyas are climbing vines whose adventitious roots attach them to the bark of trees. Other, less numerous, species adopt shrubby forms or remain as ground cover. Most hoyas are epiphytic, growing on another plant without parasitizing it, but some species grow in rocky crevices or in the ground like “traditional” plants. Because of this type of growth, hoyas have developed various mechanisms for dealing with drought, and are more or less succulent.
Dimensions and Flowers
When it comes to size, it’s impossible to give an average. Some hoyas are small and remain so for the rest of their lives, while others can spread out over several yards when given good support. When hoyas reach maturity, they produce peduncles on which several umbellate flowers appear (except in some species, which produce solitary flowers). The flowers are highly variable, often star-shaped with five more or less defined points. Usually white to pink, they go through a whole range of possible colors, excluding only blue and violet. They can be perfumed, and produce nectar that falls in large drops, waiting to be pollinated so they can spread seed capsules to the four winds. Some hoyas are grown primarily for their flowering.
There’s a vast selection of hoya cultivars, some common, some rare and coveted, some disconcertingly easy, some unsuitable for indoor cultivation, some whose foliage is particularly pleasing, some whose flowers you want, some frightfully expensive… With such extremes, this article will be long enough without my pretending to tackle the impossible task of presenting all the hoyas in the world, or even all the easy indoor hoyas. I will therefore present the cultivars most commonly available in Canada.
- H. carnosa is the “traditional” hoya with green leaves and white flowers. Ultra-easy to grow, but slow-growing.
- H. carnosa H. carnosa ‘Krimson princess’ or ‘Rubra’: I don’t know if there’s a difference between these two cultivars, but it’s a variegated hoya with the variegation in the heart of the leaf. When it gets enough light, the leaves take on a pink hue that fades over time. Like many variegated plants, it sometimes turns green again, especially when it lacks light. The flowers are white or pink.
- H. carnosa ‘Krimson queen’: variegated hoya with white variegation around the edge of the leaf. Occasionally, it creates all-white leaves which, while pretty, don’t photosynthesize, weaken the plant and die off more quickly. On a small plant, it’s best to remove them. Flowers are white or pink.
- H. carnosa compacta: mutation of H. carnosa with curly leaves. Growth is particularly slow and the stems eventually collapse under the weight of the leaves. Apart from its funny leaves, it behaves like H. carnosa. It also comes in a variegated version.
This time, the family is native to Australia. Hoya australis is a little less common, with slightly rounder foliage. It’s easy to grow, but less tolerant of low-light situations than the hoyas mentioned so far. ‘Lisa’ is the name given to the variegated cultivar of H. australis.
This is a hoya from another family, originally from the Philippines, which is easy to grow and a little faster than H. carnosa. It can be distinguished by its lanceolate foliage. Various cultivars exist, with flowers of different colors (white, red or crimson) and distinctive leaves: for example, they can be spotted (‘Supersplash’) or very dark (‘Hawaian Prince’).
One of the most succulent hoyas, it’s a favorite on Valentine’s Day for its obcordiform leaves. A small, rooted leaf is often sold, but it can also be found in a more traditional version, with stems and leaves, and of course in a variegated version. Beware of over-watering: with its succulent nature, it tolerates drought well. Best grown in direct sunlight.
As its name suggests, this hoya has retuse leaves, i.e. a rounded apex with a small, shallow notch. In short, the leaves resemble blades of grass. This is one of the hoyas whose flowers do not grow in clusters, but are solitary. As its leaves are thin, it’s a good idea to let the soil dry out… but not for too long!
The leaves also resemble blades of grass, as with H. retusa, but they are denser on the stem and the flowers grow in clusters. From a distance, it looks a little like Spanish moss (Tillandsia usneoides), but only in appearance. Cultivation is similar to that of its look-alike, H. retusa.
Leaves are oval to lanceolate. Flowering is said to have a cinnamon scent, hence the name Cinnamon Hoya. It is also sometimes called H. suaveolens for the same reason. Its cultivation is similar to that of H. carnosa.
H. kentiana et shepherdii
Although these are two distinct species, they are so similar that they are often mixed up. Here, the leaves are very lanceolate and look a little like bean pods, hence the nickname String Bean Hoya. H. kentiana also exists in a variegated version. Easy to grow.
Adorable little hoya with heart-shaped foliage and leaves dotted with silver spots. Tolerant of low light, which nevertheless slows its growth, it should not be over-watered, because, although the leaves are small, they are succulent.
A miniature hoya whose cultivation is significantly different from that of the other families mentioned above. It offers cute little leaves on stems that never climb. The H. bella blooms in clusters of around 8-10 flowers, abundantly in generous light. It will have its own section after the cultivation tips for more “traditional” hoyas.
It also exists in variegated versions (‘Luis bois’ for variegation at the heart of the leaf and ‘Anneke bois’ for variegation at the edge of the leaf blade). As there is no authority on the names of hoyas, there are other nomenclatures which designate more or less the same plant).
There really are some weird hoyas! We’ve mentioned the curly hoya (H. carnosa compacta), but there’s also a hoya whose leaves seem perpetually short of water (H. imbricata), a hoya with flowers like shooting stars (H. multiflora) and a hoya whose stems resemble a fish tail (H. polyneura), to name but a few!
Hoyas accept a wide range of light conditions. It is accused of being slow-growing, but it is often placed in medium or even low light. It will survive… but won’t do much other than survive! Ideally, it should get as much light as possible, even direct sunlight.
The water requirements of hoyas depend on their succulence: a hoya with plump leaves, such as H. kerrii, will tolerate drought better than one with small, thin leaves. However, all hoyas are more afraid of staying in perpetually damp soil: so try to water them when the soil is several centimetres dry. If in doubt, wait a few days. Most hoyas recover well even if you forget to water them.
Although it tolerates the dryness usually found in homes, it will benefit from increased humidity.
Soil and Potting
With its small, epiphytic root system, the hoya likes light, airy potting soils: we’re talking about potting soils for cacti or succulents, or even potting soils for orchids, or a mixture of these two with traditional potting soil.
You can even plant hoya on a plate! See more detailed article.
The hoya tolerates looooooong years in the same pot and in a restricted space. While it has a high tolerance for many things (light, dryness, narrowness of pot), it is adamant about one thing: adaptation! Yes, a simple change of location can give it a shock. So avoid unnecessary repotting and frequent changes of location.
To find out whether a hoya needs repotting, look to see if the roots are protruding through the drainage holes, if the soil dries out within a few hours, or if the plant is perpetually thirsty. These are all indicators that it’s probably time to repot.
Repotting is done in the same way as for all houseplants, but extra care should be taken to disturb the root ball as little as possible. Repot into a slightly larger pot.
Do hoyas bloom better in tighter pots? Rumor has it, but is it a horticultural myth? One thing’s for sure, it won’t flower if it’s adapting to a change (moving, repotting), so you kill two birds with one stone by leaving it in a tight pot!
With hoyas, patience is the key: they can take up to 5 or 10 years to bloom! But they reward our patience with beautiful, fragrant flowers at night (…or not fragrant at all, as in the case of my Hoya bella, which is flowering generously even though it was a cutting only a year ago, but smells of absolutely nothing).
All-purpose fertilizer during the growing season, but at a lower dose than indicated on the pack.
The hoya is quite unusual in its growth: it appears immobile for a few months, then suddenly grows at breakneck speed, before going back to sleep. This is not abnormal for it. It will also tend to produce long, apparently leafless stems. However, if you look closely, tiny leaves are present on these particular stems (called tendrils instead of stems). The leaves will eventually grow, but hoya can take months to produce leaves on bare stems. This is exactly the time to attach it to a support, as there’s less risk of damaging the leaves.
Tropical temperatures between 15 and 29 degrees Celsius will suit it perfectly all year round.
The slow-growing hoyas love to go out and bask outdoors in the summer sun.
No problem for cats, dogs abd babies: hoyas are non-toxic.
Slow-growing plants are usually low-maintenance, and hoya is no exception. Occasionally, a yellowing leaf is removed and that’s it. It also appreciates being cleaned when it gathers dust. If it’s not in a basket and drooping, you can attach its stems to a trellis to give it the shape you want. If you’re lucky enough to have flowers, simply remove them when they wilt or sweep the floor. Watch out, though, for the abundant nectar from the flowers, which can stain floors and furniture!
Pruning is rarely necessary, but can be done if more compact or orderly growth is desired (personally, I’m partial to slightly chaotic hoyas – I think they’re a good example of a plant that grows and flowers when it wants to!) Pinching the ends can stimulate branching. Be careful not to cut just anywhere: the peduncles can flower more abundantly every year. Read more about pruning in this article.
Caring for Hoya bella
And the Hoya bella?
I’ve reserved a special section for the particular cultivation of this hoya and for all the others with slender, barely succulent leaves (for example, H. polyneura also falls into the same category). This is because their cultivation is a little more delicate.
o Light: average, but in generous light it flowers all year round. Hoya bella can withstand a little direct sun, but is less tolerant of drought than the others, so care should be taken when placing it in the sun.
o Water: frequent watering, keeping potting soil slightly moist at all times.
o Potting soil: for indoor plants, with a few draining elements. Avoid orchid potting compost, which doesn’t retain enough water for H. bella.
o Care: although it is often presented on a trellis, it does not produce adventitious roots and therefore does not really climb. Stems are born straight, then hang down under their own weight.
In all other respects (humidity, potting, fertilization and temperature), it can be grown in the same way as other hoyas.
Don’t be scared off by these more capricious conditions: personally, H. bella is one of my favorite plants and my favorite hoya! It’s a fast-growing plant that’s perfect for hanging baskets, thanks to its drooping habit and generous flowering. Unlike other hoyas, the peduncles fall away once flowering is over. Sporadic pruning encourages branching (it seems to flower only on new branches). Mine is in front of a south-facing window, in full sun, and it blooms all year round. Admittedly, cultivation is more delicate than for other hoyas, but oh so satisfying!
Stem cuttings can be taken in water or soil. Individual leaves can form roots, but without a piece of stem, will not produce a whole plant. Even with a piece of stem, the cut leaf may take several years to produce a second leaf. For more information, read this article.
- Wrinkling leaves: lack of watering. If the potting soil is dry, the plant is greatly dehydrated, and should be watered abundantly to moisten the potting soil (watering in basins may be necessary). If the soil is still moist, but the leaves are wrinkled, rot may be affecting the root system.
- Long leafless stems: this is normal for hoyas. The stems will eventually take on leaves.
- Ravageurs: cochenilles diverses, thrips, pucerons.
- Loss of flower buds or new leaves: lack of water, lack of light, too much ambient dryness. In my experience, despite our best efforts, hoyas sometimes abandon new growth, which dries out and falls off while still small. These small losses are rarely fatal for the plant. We mourn the loss and the plant resumes its growth without too much trouble!
Hoyas are generally sold as hanging plants and don’t suffer from this treatment at all. However, you can also fix it on a stake of any shape you like (they’re often seen on a round stake); this is particularly easy to do when it produces its long, leafless stems.
Very fashionable at the moment, the hoya is one of the best houseplants: it tolerates variations in growing conditions, including light and water, it adapts to the usual humidity in our homes and, above all, both its leaves and flowers are attractive. For a bigger challenge, choose thin-leaved hoyas, such as H. bella, which are more delicate to grow. The only downside to hoyas is that they can be addictive and turn you into a hoya collector… We’ve had worse, haven’t we?