Anyone who had a grandmother who was passionate about plants will almost certainly remember a vine that climbed the kitchen walls, with shiny leaves and clusters of small flowers that seemed to be made of porcelain. That plant was probably a Hoya carnosa, also known as wax flower or porcelain flower, belonging to the family of Apocynaceaethe same as, among others, the oleander and the periwinkle. A tropical indoor plant that has won over generations of enthusiasts due to its extraordinary resistance, the ability to grow for years and the natural beauty of its flowers, delicate and fragrant.
Description of Hoya carnosa
Hoya carnosa belongs to a genus that includes over one hundred different species, native to the regions of eastern Asia. These are evergreen perennial climbers that in nature often grow as epiphytic plants, clinging to tree trunks in tropical forests. Some varieties crawl on the ground, others colonize rocks. In ideal conditions, the largest species can reach eighteen meters in length, climbing thanks to a system of intertwining and adventitious roots.
The leaves are the first striking feature: thick, fleshy, of an intense and shiny green that seems covered in a layer of wax. This particular texture gave rise to the common name of the plant, precisely “wax flower”. The leaves are arranged in opposite ways along the stem and can have very different shapes depending on the species: from almost perfectly round to linear, from tiny (just five millimetres) to gigantic (over twenty-five centimetres). Some varieties display irregular silvery spots on the surface, which add a decorative touch to the foliage.
The flowers of Hoya carnosa
The real show comes with flowering. The flowers of Hoya carnosa come in umbrella-shaped clusters, each composed of small, perfect five-pointed stars. The petals are thick and waxy, just like the leaves, and in the center is a complex structure called the crown, which is also stellate. The result is a flower that seems sculpted in porcelain, delicate yet resistant.
Colors range from pure white to intense pink, with variations including orange, red and even greenish tones. Many varieties produce a sweet and intense scent, while almost all secrete abundant nectar. In nature, these flowers attract moths, flies and ants, which take care of pollination.
The flowers arise from particular structures called spurs, which grow from the leaf axils. A fundamental aspect for those who grow these plants: the spurs should never be cut, they are perennial and with each flowering cycle they lengthen further. In the most vigorous species they can reach up to twenty-seven centimeters in length.
Where to place the Hoya carnosa
The first rule for successfully growing a Hoya carnosa concerns exposure. These plants love bright but indirect light. The waxy foliage might make you think of a succulent that tolerates direct sun, but this is not the case. Hoya is a tropical plant that grows in nature in the shade of trees, protected by the forest canopy. The afternoon sun, too intense, can burn the leaves.
The plant survives even in low light conditions, but in this case it will hardly produce flowers. Those who wish to see the characteristic starry umbels must guarantee the plant a bright place, perhaps near a window facing east or west, where the light is abundant but filtered.
Which soil to use for Hoya carnosa
Hoya carnosa needs a very particular substrate. The key is air circulation: the roots must breathe. A compact universal potting soil is not suitable. The ideal mixture is prepared by mixing equal parts of orchid soil, succulent soil and perlite. This mix ensures drainage
perfect and prevents water from stagnating around the roots.
A curious characteristic of these plants is that they love narrow spaces. Not only do they tolerate being root bound, but they often flower better under these conditions. Repotting is only necessary every two or three years, when there is simply no more space. And when repotting, it is best to choose a container that is slightly larger than the previous one.
How to water Hoya carnosa
Watering is a delicate point. From spring to summer, when the plant is in the active growth phase, the water must be regular: water it when the upper layer of soil feels dry to the touch, using water at room temperature. The important thing is to let the substrate dry well between one watering and another.
In autumn and winter the plant naturally slows down its metabolism and consumes much less water. At this stage, watering must be drastically reduced: only water enough to prevent the soil from drying out completely. Overwatering is one of the most common mistakes and can cause flower drop or, worse, root rot.
Ideal humidity and temperature for Hoya carnosa
Being a tropical plant, Hoya carnosa appreciates high levels of ambient humidity. In winter, when heating systems make the air in the house particularly dry, it is useful to resort to some tricks. A humidifier is the best solution. Alternatively, you can place the plant on a saucer filled with gravel and water: evaporation increases local humidity. Spraying with room temperature water also helps, but it is important to avoid wetting the flowers directly.
As for the temperature, the plant does well in normal domestic conditions, with one caveat: it is better not to drop below fifteen degrees. The plant must be kept away from windows in winter and from air currents from air conditioners in summer.
How to prune Hoya carnosa
Hoya carnosa requires minimal pruning. The main intervention is done in spring, before vigorous growth begins. Branches that are too long or disorderly can be shortened, but with one fundamental precaution: the spurs, those apparently dry twigs from which the flowers will grow, must never be touched. Even if they seem useless, they are the secret of future flowering.
The plant has a naturally climbing or trailing habit. You can let it hang freely from a shelf or hanging pot, or you can guide it up a vertical or circular trellis to give it a more compact, tidy look.
How to fertilize Hoya carnosa
Fertilization is important, especially if you want to achieve lush flowering. A liquid fertilizer specifically for orchids, rich in phosphorus, is ideal. Phosphorus is the element that stimulates and supports flowering. It is administered once a month from spring to autumn, while in winter it must be completely suspended.
Patience: the virtue of the Hoya carnosa grower
One of the most frustrating aspects for those who grow Hoya carnosa is waiting for the first flowering. These plants must reach full maturity before producing flowers, and this can take five to seven years. Some varieties flower earlier, others take even longer. There are several documented cases of plants that waited up to 30 years before flowering for the first time.
If the plant is mature but still does not flower, the causes could be of various nature. Often it is simply a question of insufficient light, other times there is a lack of the right nourishment in the soil. Some varieties require very specific conditions: they want to be root bound, or they need a dry period in a certain month, or they require a change in light exposure.
An advice that expert growers always repeat: do not move the plant, especially during the growing and flowering season, because Hoya carnosa does not like changes and could become “offended” to the point of refusing to flower.
Symbolic meaning of Hoya carnosa
Beyond the practical aspects of cultivation, the wax flower carries with it a profound symbolic meaning. In many cultures it is associated with eternal loyalty and unbreakable bonds. This symbolism derives from the very nature of the plant: resistant, long-lived, capable of flowering for years if cared for with love. In Asia it is considered a lucky charm that attracts prosperity to domestic environments, while in the West its great decorative beauty is appreciated above all.
