Despite the fact that almost every day I write this blog (I can’t cope with doing it on the move) I can look at my hoya if I lift my eyes above my laptop, I have managed to avoid mentioning it. I bought the plant two years ago at a church fair on the plant stall and it was a lopsided single stem tied to a split cane. As such I am not sure of its precise name and it looks for all the world like Hoya carnosa, the common wax flower, apart from the random silver speckles on the leaves. There are forms of Hoya carnosa that have this leaf marking so in the absence of any more accurate name I will call it this.
Hoyas are a frost-tender genus in the asclepias family* and most come from the Indonesian area. Hoya carnosa is from China and was the first to be described in the West and was named after Thomas Hoy in 1810 (or 1809). It was named by Robert Brown who studied medicine but is best remembered for his ‘discovery’ of Brownian motion of molecules in suspension. He was a botanist too and erected the family Aslepiadaceae to differentiate its plants from Apocynaceae because of the way the pollen is held in sticky packages, something that is seen only in this family and in orchids. Thomas Hoy was the Head Gardener at Syon House in London.
There are about 300 species of hoya and they have opposite leaves and most are epiphytic, growing on or up trees. My plant has traces of aerial roots along the stem as though it wants to cling onto something. Flowers vary in colour from white to deep maroon and some are green, yellow or orange but none are blue. They are often sweetly scented but, in common with others in the family (or families) some smell unpleasant. Lots are in cultivation but the only ones commonly sold are this one, Hoya bella which is a compact plant with smaller blooms and H. multiflora, sometimes called ‘Shooting Stars’ which is upright and bushy with yellow and white flowers. Then there is H. kerrii which is sometimes called the sweetheart vine because the leaves are heart shaped. It is sometimes sold as a novelty with one, rooted, leaf in a pot. As I found out many years ago, you can root a hoya leaf but it will never actually make a plant, just survive for many years. It seems a bit ‘frankensteiny’ to me.
Hoyas are often collected by fanciers of cacti and succulents and they fit quite well – hoyas are rather succulent with waxy, plasticky leaves. Hoya carnosa makes a good houseplant, with a couple of caveats, that is easy to look after and has pleasantly scented flowers. It can grow 1m a year so you need to have some sort of framework to train it around. Most references say it needs good light but it will tolerate shade but then is unlikely to flower. References also say it should have no direct sunlight and when I have grown it in a greenhouse next to my cacti it did have rather yellow, scorched leaves but flowered prolifically. This plant is in a south-facing window, or has been all winter, but if it starts to scorch I will move it to a window facing west. Last year it had three clusters of flowers but it now has over a dozen, with more forming.
The flowers are white, blushed pink, with a red centre, carried in clusters of 20 or more, and they drip nectar. This is one of the reasons why it is not a perfect houseplant – when the flowers drop they make a bit of a sticky mess so don’t stand it on your aunt’s favourite lace doily. One of the oddities of this plant is that the flower stem (peduncle) that carries the individual flowers, should be left in place once the blooms have dropped because more flowers will grow from it every year. I can not quite decide what the flowers smell of. They are pleasant but sometimes have a spicy note, especially at night, that I won’t quite rave about.
It does not need high winter temperatures if it is kept quite dry and 5c is fine though more is beneficial. Good light, a winter rest and cooler temperatures, together with water and feeding in summer will keep it growing and flowering well.
* As is the way with things botanical asclepiads are now in the sub-family Asclepiadaceae which is in the family Apocynaceae, the family that contains vinca. It must be a nightmare for botanic gardens which have ‘order beds’ with plants arranged by families. It must be tempting to pot them all up so they can keep moving them from one bed to another according to the latest research or whim of the botanists!