About Hoya carnosa

Description

The wax plant, scientifically known as Hoya carnosa, is a member of the dogbane (Apocynaceae) family. Specifically, it belongs to a subfamily called the asclepiads or milkweeds, a name that references the latex-like milky sap that its members produce. In fact, if you’ve ever , you might notice the striking similarities in the dainty, star-shaped flowers.

Natural habitat

This popular houseplant is native to (sub)tropical areas in Asia. Specifically, it’s naturally found in China, Laos, Taiwan, and Japan, although some sources also note its presence in Queensland, Australia, as well as Fiji.

Hoya carnosa prefers tropical or subtropical rainforests. Here, it grows mostly like an epiphyte or lithophyte: on trees (in a non-parasitic manner) or on rocks, using any bits of soil or debris present to help anchor itself. (This behavior can be seen on other epiphytic/lithophytic houseplants, including favorites like Hoya kerrii, Syngonium podophyllum, Peperomia prostrata, Tillandsia, and Epiphyllum.)

Wax plants are vining in nature and can climb to great heights if given the opportunity.

Hoya carnosa varieties

If you want to know more about the different cultivars and hybrids of Hoya carnosa, it’s important to keep in mind that this topic is widely disputed. Like, really disputed, as far as plants go. There are some old, established cultivars, but there are also many whose origins seem a little iffy.

Hoya enthusiasts often note that nurseries will slap any name on an unpatented wax plant variety just to be able to pretend it’s something shiny and new. This allows them to sell the plant for more money, sometimes into the hundreds of dollars!

That’s why you should take any new wax plant variety being hyped online (which happens a lot) with a grain of salt. It’s always a good idea to think twice before shelling out a lot of money for a Hoya.

It doesn’t help that there’s no real directory available, nor official control besides patents (which definitely aren’t always filed). I’ve tried to gather the most extensive information possible to hopefully shed some light on the matter and clear up some confusion!

In addition to the more common Hoya varieties discussed in my Hoya plant roundup, you’re also likely to come across these cultivars:

• Hoya carnosa ‘Stardust’: A freckled variation similar to ‘Freckles Splash’. Looks pretty much identical.
• Hoya carnosa ‘Wilbur Graves’: Also sports splashy leaves. Looks very similar to the previous splash cultivar, but goes for $100+ for some reason. This is despite the fact that its origins are pretty unclear and widely disputed! 
• Hoya carnosa ‘Chelsea’: Features heart-shaped leaves that look dimpled. Note that six dimples per leaf indicates you’re dealing with a ‘Chelsea’ rather than a ‘Krinkle 8’. 
• Hoya carnosa ‘Jade’: Sometimes simple is best, so this one has fully green leaves with no splashing or variegation.
• Hoya carnosa ‘Brazil’: Apparently the result of a “cross” between ‘Rubra’/’Krimson Princess’ and ‘Chelsea’ or ‘Compacta’… but really, it’s so similar to the former that you might as well buy that one.
• Hoya carnosa ‘Snowball’: Bred by a well-known Hoya grower named Genevieve McDonald. It’s similar to a ‘Tricolor’, but has more rounded leaves.
• Hoya carnosa ‘Amore’: So similar to ‘Chelsea’ that it’s sometimes used as a synonym for that one. If you like them, just go for whichever’s cheaper.
• Hoya carnosa ‘Holliana’: Quite a unique variety, with small, crinkly and variegated leaves.
• Hoya carnosa ‘Nova Ghost’: Apparently a reverted ‘Argentea Princess’, meaning a plant that has lost its variegation, by KOKO Ranch. Remember that grey varieties of H. carnosa are pretty slow-growing.
• Hoya carnosa ‘Grey Ghost’: Very, very similar to ‘Nova Ghost’, and not much information out there about its origins. Despite this, it’s generally cheaper than its twin!

Caring for Hoya carnosa

Light and temperature

Scientists have actually done a bit of research into Hoya carnosa light requirements. They found that sometimes, data suggested that the plant was better adapted to shaded conditions under the forest canopy. Other times, though, it seemed to prefer exposed conditions, or full sun. 

Conclusion? Both seem to work well, which makes sense for a climbing epiphyte/lithophyte like this. After all, some of its leaves can be under the canopy, while others are exposed to full sun.

In the home, the best way to ensure yours grows well without burning is to place it next to a window that receives bright, indirect light. Artificial lighting (grow lights) also works well.

In terms of temperature, this plant is relatively forgiving. Unlike many of our tropical favorites (Alocasias, I’m looking at you), Hoyas also grow in subtropical forests, meaning they’re better adapted to chilly conditions. They prefer temps of 59°F or up, but will generally be fine as long as they’re not exposed to frost.

Water and humidity

Although its waxy leaves may seem to suggest that you should treat your Hoya carnosa like a succulent, that’s not exactly the case. After all—as we discussed in the section on habitat—this species actually naturally grows in rainforests! 

It’s true that these forests can be subject to dry periods, which is why wax plants evolved to be semi-succulent and are pretty forgiving about underwatering. However, they really do prefer plenty of moisture.

For the best results, water your Hoya carnosa once the top of its soil has dried out. During the active summer months, you can water when the first 2 inches or so feel dry when you stick a finger into the pot.

In winter, when houseplants need less water, it’s generally better to wait until the soil has dried about halfway.

Soil and planting

As you’ve read in the section on Hoya carnosa’s natural habitat, this houseplant naturally grows as an epiphyte or lithophyte. It uses rocks or trees as support while it climbs its way to the top of the jungle, rather than growing in soil. 

Fertilizing

Because Hoya carnosa isn’t exactly the quickest grower among houseplants, the species isn’t a very heavy feeder either. That doesn’t mean it won’t enjoy a little boost during the active summer growing months, though!

You can use a balanced regular houseplant fertilizer once or twice a month to make sure your wax plant grows well. Some enthusiasts recommend switching to a fertilizer that has a little more flower-boosting phosphorus if it looks like your plant is gearing up to bloom, but this isn’t a must.

Pruning 

Your wax plant won’t need much in the way of pruning. You can remove any dead or unsightly leaves, but if you cut entire vines for one reason or another, it would be a pity to discard those. Instead, head over to the section on propagation in order to find out how to multiply them.

Dividing or repotting

Good question! Most specimens of Hoya carnosa consist of several vines rooted in the same planter. This means that once the plant outgrows its pot, you could consider separating one or two of these to give the remaining vines more space.

This being said, most folks prefer a fuller look, which removing vines can take away from. If you’re in this camp, repotting can be done by refreshing the soil and going one pot size up during spring. Since these plants don’t mind being a bit cramped, it’s probably not something you’ll have to do every year.