There's something about Hoyas that turns people into fanatics, and by "something" I mean flowers. And this is perfectly understandable, because the flowers, while not up to Gardenia jasminoides' standards, are nevertheless pretty cool: scented, profuse, relatively long-lived, and curiously-textured, they have an alien quality to them that at the very least grabs the attention.1
This poses certain daunting obstacles for a non-fanatic, non-specialist blogger, though, because the enormous fan following means that there are huge numbers of websites out there, with all kinds of information on each little nuance of the differences between Hoya species and cultivars and crosses and on and on. I mean, there's even a Hoya forum at Garden Web, with (as I write) forty-two pages of posts to be gone through, and you can see how forty-two pages of posts, each with roughly twenty posts, each post of which averages, say, three or four pages in length, plus all of the individual Hoya blogs, publications by Hoya societies, mentions of Hoyas in houseplant books, and so on and so forth, might represent more material than any one man is going to be able to sift through. Or at least, more than one man is going to be able to sift through in three or four days, which is the usual amount of time I allow for one of these posts.
Another sort of intimidating part of this one is the knowledge that if I get anything wrong, a thousand screaming Hoya fans will descend on me to tell me how wrong I am, and since different sources of information disagree, anything I say will inevitably be viewed as "wrong" by someone or another.
Consequently, this post has been an incredible pain to write, and I am even right at the moment all but having to tie myself to the chair in front of the computer to get something down. This isn't necessarily your problem, and I don't necessarily expect you to care, but if you needed an explanation for the nine-day delay between plant profiles, there you go. Please note that if you disagree with something herein, I do actually want you to leave something in the comments telling me why it's wrong, and what would be right: I do get a fair number of Google searches here from people looking for information on one plant or another, as well as the occasional non-plant, somewhat heartbreaking query ("after 20 years does the exboyfriend have feelings for the exgirlfriend," "i think my roommate might be a psychopath"), non-sequitur ("damsels in distress thumbs") or the occasional headdesk2 ("who invented tradescantia pallida plant"3). So for the people who get here by looking for plants, I do want to have accurate information, or at the very least I want to not be perpetuating misinformation. So do share if you know something in here is wrong (but be prepared to argue your case).
The only Hoya species I have direct personal experience with is Hoya carnosa. There have been three other species at work, but I don't have positive IDs for them, nor do I particularly care on two of the three.4 The third plant actually is of interest to me, but I don't have an ID for it either, so I'd be eternally grateful to any readers who know what it is and want to say so in the comments:
Anyway. So the only species I know particularly well is H. carnosa, but I have a fair amount of experience with it, by now. I'm not a fanatic (yet), but I have six plants, one 'Krimson Queen,' one 'Exotica,' two 'Chelsea,' and two batches of 'Exotica' cuttings that I brought home from work. 'Exotica' seems to have a pronounced tendency to revert to all-green and lose variegation. Since a stem with all-green leaves has an advantage over a variegated one (all-green leaves mean more chlorophyll, which means more energy-collecting capacity, which means more food production), given a long enough time, they will take over a pot. So part of maintenance for variegated Hoyas is removal of the all-green stems, which is where those last two of my plants came from. And they're plain, but they seem nice enough, even so.
'Krimson Queen,' on the other hand, seems especially prone to throw out stems that are solid white, instead of green. Though interesting and pretty, these are probably best removed from the plant as they appear, because they contribute nothing to the plant while taking resources to grow. I've permitted this one:
because it is pretty, and because I figure there are enough individual stems in the pot that even if one of them dies because of the white shoot, it won't matter to the overall integrity of the plant. But I should, yes, take it off.
The 'Krimson Queen'5 was my first Hoya, and was bought out of two kinds of curiosity at once: 1) can I grow this? and 2) why do so many people like to grow this? Originally just three rooted cuttings in a 3-inch pot, it has gotten to be a bit of a monster:
But then, that's after a year and a half, and it's not like I mind if it wants to grow. (Having it grow was kind of the point, obviously.) Some of the filling out was produced by taking cuttings of the original plant and, after water-rooting them, sticking them back in the pot. Hoyas in general have a tendency to grow long, leafless vines to nowhere, which fill in with leaves much later, so it helps if you plan for this, either by planting a lot of cuttings together or giving the vines something to climb (bamboo hoops and arches seem to be traditional, but it doesn't matter so much what they have to work with, so long as it's something multiple vines can use at once). 'Krimson Queen' has, for me, been extremely easy, almost suspiciously so, as if it's setting me up for a mealybug infestation of Biblical proportions later on.6
Which, since I mention it: mealybugs are the primary bane of the Hoya grower, particularly with the curled-leaf varieties like 'Hindu Rope,' the curved surfaces of which provide a bajillion little hiding places that spray pesticides won't be able to reach. I recommend going straight to the systemics; don't even bother with rubbing alcohol sprays. (It still makes sense to do the Q-Tip-and-rubbing-alcohol thing with the bugs you can see; you're just not going to be able to get rid of the bugs using that alone, not on a 'Hindu Rope.') The family Hoyas are in, the Asclepiadaceae (the milkweed family, which if you look at the picture of milkweed flowers here you can easily see the family resemblance), is also supposed to be especially appealing to aphids, though I haven't experienced this myself, and don't expect to indoors.
'Chelsea,' which was identified for me by the good people at the Garden Web Hoya Forum, has heart-shaped, dark green leaves, and, while mostly well-behaved for me, is a good example of another common Hoya issue: they pout. Granted, this isn't a life-or-death issue, as mealybugs might be, but it's unnerving: when I got this plant, I brought it home and immediately took some cuttings, as insurance against anything happening to it. And then I waited and waited and waited for the original plant, or the cuttings, to do something, for a good three or four months. This is frustrating, but so long as the plants aren't dropping leaves or shriveling or anything, it's not something to worry about. Speculation on the GW thread where I posted a question about this was that when the plant "pouts," it's probably actually preoccupied with root growth and development.
I've had other plants act like this in the past,8 and my other Hoyas all seem to go through regular cycles of growth and rest, to kind of a ridiculous degree sometimes. They don't seem to want to do anything until late December, and then they start pumping out new growth in every direction at once. This is noteworthy both because it's pretty darn striking, and because it's not what they're "supposed" to do. They're "supposed to" grow in the summer and then go dormant in the winter. Mine seem to grow in winter and spring and then go dormant in the summer and fall. Perhaps they're confused by the heating and air conditioning.
But anyway. Basic care goes like this:
Light: Bright indirect to some sun. Mine are all in a slightly-obstructed west window except for one (which gets artificial light only), and that seems to suit their needs just fine.
Temperature: This is kind of a contentious subject, with different people advising wildly different things, but my best guess is that these shouldn't get cold. Supposedly they can survive pretty cold temperatures (down to 40ºF / 4ºC, possibly lower) with no problem, but another site said that they'll go dormant if they get below about 65ºF (18ºC). Since very few of us actually want our plants to go dormant if they don't have to, I say keep them warm, but don't panic if they get cold, because it'll probably be okay.
Humidity: Seems not to be an issue, though some sites advise increasing humidity for cuttings, which I'm not sure if I endorse or not. I've never gone to any extra trouble with my own plants.
Water: I let mine get pretty dry between waterings. If they're too dry, the leaves will shrivel visibly. Too wet, and leaves will yellow and drop. Too wet is worse than too dry.
Propagation: From cuttings. I've taken tip cuttings and rooted them in water or soil, either of which seems to work just fine. I've also seen cases where individual leaves have been rooted and eventually grew new shoots, though I haven't tried it myself and it seems to take a long time and I make no promises about it working. I just know that people do it with H. kerrii in particular, and that in that case new growing tips allegedly don't ever form, but I've seen the claim that with H. carnosa they do. Clearly more investigation is in order.
Feeding: My understanding is that these are supposed to be relatively heavy feeders, though like any plant they can be damaged by too much fertilizer, so use some common sense and restraint unless you really know what you're doing.
Grooming: On my own plants, grooming has been an almost completely nonexistent issue. About once every six months I pick off a yellow leaf or something.
For flowers, one has to have a certain amount of patience, since plants have to be both of a certain age and properly motivated before they will bloom. There's no specific age needed, exactly: I've seen people on-line say that plants must be five years old, or seven years old, or two years old, or nine years old. Two other sites went with size, instead of age, and said that a vine won't bloom until it's three feet long or more. I don't think the size and age requirements can be that specific, but I think you're fooling yourself if you expect flowers the first year, and most likely the second as well. After that, all bets are off. Proper motivation means that the plant is receiving enough light, has a decently-developed root system, and has enough food. A couple of sites suggested giving a reluctant older plant a shot of low-nitrogen fertilizer, which may be worth a try.
I see the advice repeated over and over that plants are more likely to flower if they're rootbound. Something about this seems wrong to me, because no plant ever likes to be rootbound, and people say that about Spathiphyllum spp. too but I'm convinced that the only real effect of keeping a Spathiphyllum rootbound is that it becomes that much harder to water it properly. I have rootbound and not-rootbound spaths at home right now, and the not-rootbound ones are the ones with flowers. Just FYI. What I think might be going on here is a confusion of cause and effect: if plants have to be a certain age before they'll flower, and roots grow along with the rest of the plant, for any growers who don't compulsively repot every year, the plants old enough to flower are also going to be the plants that are tight in the pot. Being tight in the pot didn't cause the flowers: it, like the flowers, is a side effect of the plant getting older. Like I said, this is just a theory I have, but the theory makes more sense to me than the idea that there are plants out there that just naturally like to grow in containers.
The flowers are produced on a short stem that branches off of the main one; this is given the special name of "peduncle," and the actual group of flower buds is the "umbel." New umbels look a little bit like an old-style radio microphone: see the picture below. Flowers should be allowed to fall off of the peduncle on their own; a new umbel will form on the same peduncle the following year. (Unless you've cut it off.) It's not uncommon for buds to fall off before opening; I don't think there's necessarily anything you can to to make sure that this never happens to you, but obviously you don't want to stress out a plant that's about to flower, whether by moving it or letting it get too dry, wet, hot, cold, or whatever.
The flowers have a strong scent, and also secrete a sticky, sweet-tasting nectar. The nectar is apparently safe to eat, because I ran into a few people commenting on the taste. And Hoya spp. aren't listed as toxic on any of the toxic-to-pets lists I ran across, so there's no reason to worry about it exactly, but still, why tempt fate? Taste if you like, but try not to make it a major source of calories in your diet. You're not a hummingbird,9 and it may not be entirely trustworthy. Especially if you're fighting off a mealybug attack with systemics.
Flowering can allegedly occur whenever the plant's not having a rest period, though most of the sites I ran across also said that winter is the rest period, which is demonstrably not true for my own personal plants. Most of the actual flowers I've seen personally have been in the late summer and fall; most of the sites say spring or summer; I throw up my hands and say plants will flower whenever they damn well feel like it.
Both nectar secretion and scent are stronger at night than they are during the day, and on this one point I have actual science you probably haven't heard of backing me up. According to the linked article, nectar and perfume production maxes out at around midnight. Why is this something science cares about? I don't know. Nor can I even think of any good possible reasons. But I also can't think of any ways this information could be used for evil, so I say let's fund more of this.10
In any case, if you have a Hoya that's blooming heavily, you're going to want to put something down underneath it, because they do drip, and you probably have better things to do than try to get Hoya drippings out of the carpet. If you don't have better things to do, looking for some better things to do is a better thing to do.
I had a hell of a time trying to figure out a "person" for this plant: it's a weird mix of beautiful and weird-looking, energetic and pouty, tough and vulnerable, sweetie pie and dasher of hopes. In the end, I had to resort to sticking a combination of those words into a search engine and seeing what came out; "weird-looking vigorous pouting sweet" produced a lot of what looks like fan fiction for series that I'm not familiar with, a few bits that looked like excerpts from romance novels, and one page of music reviews for music I don't know. So voila, I guess. Romance novel heroines, as I understand the type, are frequently pouty, sweet and vulnerable, and they're not prohibited from being tough, energetic, or hope-dashers as far as I'm aware. The whole beautiful / weird-looking angle is questionable, but even so, it's a better choice for a personality than anything I was coming up with on my own, so let's go with it.
Photo credits: pictures of flowers are from the Wikipedia article for Hoya carnosa, with the close-up being credited to "fastson" and the longer shot to Yvan Leduc. The peduncles, as noted, belong to Tracy at dAmN pLaNtS. The other photos are my own.
1 I think they're kind of what would happen if you described "flowers" to an artistic genius who had never seen an actual flower and then asked him/r to construct some based on the description.
2 I don't know a better term for this. It's when someone has done something so horrible, pathetic, frustrating or idiotic that the only response you can have to it is to bang your head on the desk in front of you. My mind reels at the fact that apparently nobody ever needed a word for this before the internet came along.
3 Come on. "Invented?" You're comfortable with your use of the word "invented," there?
4 I'm in a weird situation with flowering plants at work, because generally as soon as anything blooms, it sells right away and I may or may not get to experience it. The Gardenia we had that bloomed late last November had, literally, easily 100 buds on it not too long ago, and a good deal of anticipation had built up, and then I came in one day and it was gone. When I commented: oh, yeah, it sold to some guy, said WCW, and shrugged. That's the way it goes. So while I'm sure the non-carnosa Hoyas have great flowers, it's basically irrelevant to me. And anyway one of them has already sold.
5 I feel obliged to note that I'm not 100% positive on this ID. I haven't been able to determine whether 'Krimson Queen,' 'Krimson Princess,' and 'Tricolor' are different cultivars or just different names for the same one. I also don't know, if they are different, whether it's possible to tell them apart just from the leaves, or if one has to wait for flowers. More obnoxious still, most of the galleries I ran into while trying to answer these questions are exclusively interested in the flowers, and unless you get lucky with the photos and find one that has a few leaves in the background somewhere, you're kind of screwed if you're trying to make an ID from the leaves alone. This is another way in which the Garden Web Hoya Forum is useful; they were the ones to ID my 'Chelsea,' which had previously been stumping me.
I settled on 'Krimson Queen' as an ID because of the three guesses, it's far and away the one people talk about the most, which makes me think it's probably the main cultivar in production. Given all the Hoya information out there, you'd think I could have run into something more definitive, but again, time got to be an issue. So share if you know.
6 "So Moses stretched out his staff over Egypt, and the LORD made the mealybugs in the land to prosper and multiply a hundredfold during the night. By morning they had covered every tropical and ornamental plant, and every cactus, in such great numbers that the plants appeared to be pure white, for the ground was covered with them. The Egyptians' supplies of systemic pesticides were quickly exhausted, and its nurseries were bankrupted. Yet in the land of Goshen, where the Israelites were, the mealybugs did not appear. And Pharaoh summoned Moses to him, saying, "This time I have sinned. This time I will let you go to offer your sacrifices to the LORD your god in the desert, yet you must not go very far. Now pray for my cactus, that it might be restored to health." (from the NIV, obviously)
7 Please note that there is a species of Hoya, H. kerrii, which has heart-shaped, plain green leaves, and sort of resembles this plant. On H. kerrii, the petioles (short connecting stems) attach to the leaf at the "point" of the heart, though, not at the indentation, which is one way to know the difference.
8 (I had a Dracaena deremensis 'Lemon-Lime' that didn't do much of anything for about the first year after I bought it: it grew, but only very slowly. After that first year, though, it suddenly put on about a foot and a half, kind of all at once. The plant also got moved just before it started growing faster, and may have just been responding to better conditions or something, but I think that at least some of what was going on must have been root development. I've bought another 'Lemon-Lime' since then that does not seem to be acting this way, though, that's been growing like a weed since it arrived, so I can't be positive.)
10 If I seem a little defensive here, it's because I am: I've seen way too many people whining about their tax dollars being used to fund studies about blueberry genetics or barn swallow migrations or whatever. Given the choice between paying somebody to watch beetles or paying somebody to kill a million Iraqi citizens who did nothing to us in the first place, I want my money going to the guy with the beetles. At least with the beetles, if all goes well, we've learned something at the end of it all, and we've probably not bankrupted the country doing it, either.