Plant profiles: Hoya carnosa (wax plant)
Hoya carnosa, also known as wax plants or porcelain flowers, is an old-fashioned plant that is going to make a comeback in a BIG way! Your grandparents probably had a "wax plant" and you didn't even know it - they were very popular from the 1960's to the '80s and then fell out of fashion for whatever reason. But with the revived interest in houseplants in general, Hoyas are slowly making their way back into the hearts of plant parents. Their waxy, succulent-like leaves and stunning geometrically perfect flower clusters are winning people over! For this blog post, I'm going to focus solely on the Hoya carnosa species, which is the most common species in cultivation. There are around 900 known species, cultivars, and hybrids of Hoya, so naturally not all Hoyas are created equal and many of them have different traits and care requirements. Hoya carnosa is - in my experience - one of the easiest of them all and quite happy with a little neglect! Read on to learn more about H. carnosa and its care.
A variety of variegated Hoya carnosa called 'Krimson Queen'. This variety has green in the middle of their leaves edged in white. New growth is often pink and will fade to white.
Biology: Hoyas are native to Southern India, but can be found growing wild all over Southeastern Asia and Australia. They are in the Apocynaceae family, making some of their well-known relatives milkweed and dischidia species. Like I mentioned above, there are hundreds of species and many types - some are succulent, some are non-succulent; some are woody or shrubby; some are vining; some are ephyphtic or terrestrial. Hoya carnosa in particular is a climbing type with succulent leaves and woody stems. They produce flowers in near-perfect ball-shaped clusters that are usually light or dark pink, but sometimes white. Before the flowers open, they are tightly closed buds that look almost plastic; some people have likened them to tiny candies or jewels! When the flowers open, they reveal little five-pointed star shapes that are covered in a fine coating of hair. The flowers are known to produce a sticky, sweet nectar that smells more intense at night. H. carnosa flowers smell different to everyone, it seems, but when mine flower, I get notes of honey, chocolate, and butter!
Lighting: Hoya carnosa does best in bright light, and a little bit of direct sun is just fine. In fact, some direct sun is beneficial in helping the Hoya flower. However, make sure to protect it from scorching hot summer sun! Indoors, a south or west-facing window is ideal. Variegated Hoyas like the H. carnosa 'Krimson Princess' or 'Krimson Queen' need more light, but solid green varieties tolerate much more moderate light. A solid green Hoya carnosa will be a-okay in an east-facing window. Outdoors, Hoyas will love bright shade, especially if they hang under a shady tree and get dappled sunlight.
Watering: During growing season - when it's hot and humid and sunny - water freely. In the winter, reduce your watering and make sure the soil dries out almost completely. Hoya carnosa stores water in their fleshy, succulent-like leaves, so if you forget a watering or two, your Hoya will forgive you! A good rule of thumb is to water when the leaves start to pucker just a little bit. However, letting the soil stay too dry for too long (like one might let a cactus dry out) can damage the Hoya.
Humidity + temperature: Hoya carnosa THRIVES in humidity. Other conditions like lighting and water can be less than ideal if the Hoya has high humidity that mimics their natural habitat. For this reason, Hoyas make wonderful bathroom plants if you have the right lighting! I have some of my Hoyas in more moderate humidity (around 40%) and they do fine, but I've seen a dramatic increase in growth once more humidity in introduced. Additionally, if you decide to mist your Hoya carnosa, don't do so when the plant is flowering.
These are actually flowers from an unidentified species of Hoya that I have, not a H. carnosa. However, they give you a good idea of what Hoya blooms look like! You can even see that sticky sweet nectar!
Soil + fertilizer: Well-draining soil is key, as Hoyas hate to have "wet feet." A good mix is African Violet potting soil cut with perlite and orchid bark. The AV soil is very light and airy, which helps keep the soil moist, but not soggy. Perlite and orchid bark help prevent the soil from compacting and increase drainage. Hoyas are light feeders and don't require a lot of fertilizer to bloom like some flowering plants. In fact, it's best not to fertilize at all when the Hoya is in flower, as over-feeding can discourage flowering.
Repotting: Hoyas like to be disturbed as little as possible. I wouldn't say any plant "likes" to be rootbound, but Hoyas do prefer a tighter pot and are more likely to bloom if pot bound. That said, don't repot until absolutely necessary (for example, if the tight roots are causing plant issues like yellowing leaves or you find that you have to water it constantly), and pot just one size up to keep the roots nice and snug. Never repot when the Hoya is blooming, as it will be likely to drop its flowers.
Pruning and upkeep: Hoya carnosas are fairly low-maintenance, and with proper care can last for years and be passed down among generations! If pruning, don't cut or deadhead the flowers. New flowers will continue to grow from the same spurs at the end of stems called "peduncles." Peduncles will not regrow once removed, therefore no flowers will grow! Additionally, Hoyas look lovely in a hanging basket, but can be grown up a trellis or moss pole as well.
How to get your Hoya carnosa to flower: Firstly, the Hoya must be mature (3+ years old) in order to bloom! It will need bright diffused light at the very least, but as stated above, a bit of direct sun is beneficial. If age and light are on your side, you can also encourage flowers by keeping your Hoya in a snug pot and not disturbing the roots too much. And of course, don't cut those peduncles! Once in bloom, absolutely do not repot, mist the plant, or move it around often, or it will be more likely to drop it's blooms. Given the right conditions, your Hoya is likely to provide you with nectarous blooms year after year!
Another variegated form of H. carnosa called 'Krimson Princess' - this variety tends to have creamy white centers edged in green, with pink stems and light pink to red new growth.