(This is Part II of the Ananas comosus profile, which covers how to grow one indoors. For historical, botanical, cultural, and scientific information about this plant, plus some statistically better-than-average jokes, see Part I.)
I've attempted to grow Ananas indoors three times, and only one has worked out at all. The one that worked out was a cultivar called 'Mongo,'1 which we got in where I used to work, a couple years ago when I still worked there. 'Mongo' offset prolifically --
-- so we took a bunch of the more promising offsets and planted them in three-inch pots. Something like 95% of them rooted and took off, and I wound up with one, which I've had for about a year and a half now. So I do okay with pineapple plants when they're already established.
Trying to start brand-new plants on my own, though, has been tougher. Both times, I've started from a pineapple fruit from the supermarket, and both times I've failed, though in opposite directions. The first time, I think I kept it too dry, besides also being impatient at how slowly it was rooting; the second time, I think I had overpotted it, so it was too wet, and I was so unimpatient with it that I forgot it existed for a couple weeks, by which time the base had rotted to pieces.
So I guess the first care tip is that if you have the choice, try to start out with a plant that's already rooted and established. But otherwise:
LIGHT: The recommendations on light were unanimous: pineapples need to have full sun, for as long as possible. Without enough light, plants will be too depressed to flower,2 the leaves will be smaller and narrower, and growth will be either very slow or nonexistent.
Outdoors, you have a little bit of a choice; one site suggested that the foliage (in cases where Ananas are being grown for their foliage) might actually be more attractive in a partial-shade spot, as opposed to full sun. If you're growing the plant for the fruit, full sun is still best, accept no substitutes, full stop.
WATER: On the other hand, no two people agree on pretty much anything else related to pineapple-growing. With my own plant, the 'Mongo,' I do pretty much the same thing I do for all the other plants: I let it get mostly dry, then drench it, then let it dry out again until it's mostly dry. This seems to work well enough. The impression I get is that they're fairly flexible on watering; more than one site commented on their drought-tolerance. I'd err on the dry side, as keeping your plant too wet will, of course, cause it to rot and die.
Plants being started from the tops of pineapple fruits are especially susceptible to overwatering until they have established roots throughout the soil in their pot. It may be best in these cases to water the way most people do (in small amounts but frequently), instead of the way I usually do (in large amounts at long intervals), until the plant is established.
TEMPERATURE: Again, depends who you ask. If you want fruit, people recommend keeping the temperature warm. Different people define "warm" in different ways, but on average, people say 65F (18C) or above at all times.3 It also appears to help if the temperature doesn't swing back and forth a lot: more than one site advised maintaining steady or nearly-steady temperatures.
The actual point where it's cold enough to kill a plant seems to depend a lot on the variety of plant and the length of time involved; a number of people report their plants surviving brief light freezes (to around 28F/-2C). Cosmetically, this is probably a bad idea -- the plants' growth will slow, and leaf tips will probably die back, and it could take a long time for it to look respectable again. So don't do that.
HUMIDITY: High humidity is preferred, especially if you're expecting fruit, but they'll roll with lower humidity, within reason.
PESTS: The main problems commercially are fungal, viral, and bacterial, and don't have a lot to do with the usual indoor plant pests. That said, the viral diseases (mostly pineapple mealybug wilt-associated virus, which is probably technically several different viruses) are transmitted from plant to plant by mealybugs, which means mealybugs are possible. I also read that scale is sometimes a problem. As far as I'm aware, aphids, spider mites, thrips, etc. are not significant pests of Ananas.
PROPAGATION: If you begin with a mature plant, offsets should begin to form around the base of the plant before the fruit is even ripe. This works just like with other offsetting bromeliads like Guzmania or Neoregelia; new plants emerge from buds between the outermost leaves and the center of the plant. These can be removed when they're about 2/3 as tall as the parent and potted up on their own; rooting is, as you'd expect, most likely in full sun, warm and humid air, and with moderately moist but airy, fast-draining soil.
Sometimes, the fruits will also grow multiple offsets, as in the first photo above, or this fruit that's offsetting from its base:
You never see multiple tops on the fruit in the grocery store, which I can't explain; I've also never seen offsetting from the base of the fruit, like in the picture above. Maybe only ornamental plants do these things, maybe commercial pineapples are discouraged from it somehow, maybe it just doesn't happen very often. I'm not sure. But for propagation, they work the same way. Most of the plants we had at work came from the top of the one fruit in the first photo; 'Mongo' didn't offset a lot from the bases of the parent plants.
Supposedly, according to Floridata, after fruit is harvested from a plant, the stem the fruit sits on is also capable of producing new plants. All the page really says is to strip the stem of leaves, cut it into pieces, and plant the pieces, which is not really specific enough to get a very clear idea of what to do, but what the hell, if you have a stem there anyway, you might as well experiment and see what happens.
Propagation from seeds is theoretically possible, but it's not practical for a non-professional to do inside his/r home, and it's hard to get seeds in the first place, so we'll skip that.
If you're starting out with a store-bought fruit instead of offsets, things are a little more complicated, but people still do it all the time, so take heart. The first step is to remove the rosette of leaves from the fruit, and there are two basic ways of doing this: one can cut the top inch of fruit off, or one can twist the leaves one way and the fruit the other way until the leaves come out on their own. Both are pretty easy to do; I favor the twist method because it's a better set-up for the next step.
And what is the next step? If you plant the pineapple top directly, it will likely just rot, because of the fruit that's still attached to it. So you have to clean it up a bit, to reduce the chances of rot. Cut or pull away as much of the attached fruit as you can; you might also want to leave the top in a bright, sunless spot for a couple days to permit the base to dry.
The third step is to remove some of the leaves. The new roots are going to emerge from the hard center of the plant, just above where the leaves are attached, and obviously they're not going to accomplish anything if they emerge and then find a leaf is in the way. Therefore, you want to pull a number of leaves from the bottom. The two most common rules of thumb are 1) to pull four layers of leaves away, or 2) to pull leaves away until you're left with about 1-1.5 inches (2.5-3.8 cm) of bare stem at the bottom. Whichever. (It will probably wind up roughly the same either way.) You will probably be able to see tiny white roots already on the stem when you do this.
Fourth comes rooting the top. Some root it in water first and then transfer to soil, and others start out in soil from the very beginning. I think the next time I try this (very soon -- we bought a pineapple while I was writing these posts), I want to try starting in water first, because starting in soil right off the bat doesn't seem to be working for me. However, if you have a semi-protected spot outdoors4 and a long growing season ahead of you, with pineapple-friendly temperatures, it might be fine to start outside in a pot. Use a potting mix that will drain quickly. Bagged cactus and succulent mixes are usually decent, though a good all-purpose mix with some aquatic soil or clean, coarse sand5 added might be better if you can swing it. If, on the other hand, you begin by rooting in water, you don't have to worry about soil quality immediately, though maintaining an appropriate water level (high enough to cover the roots you're trying to grow, but not so deep that it covers the crown of the plant) may be hard to keep up with, if the container is very small. One ingenious commenter at Davesgarden.com recommends using a bulb-forcing vase, like those used to force hyacinths in winter, which are about the right size to be able to keep a pineapple top in place without having to worry about the water level getting too high and rotting the crown. Try to change the water daily until decent-sized6 roots have formed, at which point you can plant it in the aforementioned fast-draining potting mix. If you're intending to grow your plant indoors, a smaller pot (4-5 inches / 10-13 cm) is probably better than a large one; if your plant is going to be outside for a while, a larger pot might need less frequent watering.
Flowering and fruiting take a while, especially in low light, cool temperatures, or cramped pots, but in ideal conditions you may have something happen around 18-24 months. If the fruit is removed, plants can fruit repeatedly, though commercially-grown pineapples are retired after 3-5 years, because successive fruits tend to be smaller and smaller, as plants age.
FEEDING: The usual recommendation is for a normal houseplant fertilizer at half-strength once a month, or quarter-strength every two weeks. You can skip this if the plant is in low light, or if it doesn't seem to be growing actively. My plant gets time-release fertilizer when I remember to feed it, which works out, I'm sure, to a lot less than the recommendation, but it would also prefer to be getting a lot more light than it does, and it's due for a repotting, so this sort of evens out.
GROOMING: Like other bromeliads, plants offset and die after flowering, but this doesn't happen immediately, and by the time it does, there are offsets there to replace it. Some other sites make it sound like everything happens all at once, really fast, and that isn't so.
Homegrown pineapple fruit, unless you live somewhere really tropical, are unlikely to be as large or as sweet as store-bought ones. Some of the ornamental variegated plants' fruits are too small or too sour to count as edible at all. Just so you know.
Actual grooming is fairly minimal: as for most bromeliads, it's pretty much limited to pulling off the occasional dead leaf. Which is not trivial, if your plant is large and spiny, but you probably won't have to do it very often.
Pineapple plants can get fairly large, even if they're in containers and indoors. It's maybe not typical, but it does happen. This specimen (belonging to Megan of Far Out Flora) was grown primarily indoors, and looks scary large:7
Most of the time, Ananas comosus is more of a novelty houseplant than a serious ornamental, grown less because anybody really wants one than because they're relatively easy to start, and sometimes one winds up with a pineapple top and doesn't want to throw it away.8 The variegated cultivars, on the other hand, are fairly decorative in their own right, even when not flowering, and I'm a little surprised that they're not available more often.9
In short, Ananas comosus is somewhat difficult indoors, mainly in that it needs a tremendous amount of light to really thrive, and it can be difficult to get a plant started in the first place. On the other hand, learn enough pineapple recipes, and you'll have a never-ending supply of opportunities.
Almost makes a person want to be a slow learner, eh?
Pages consulted for this post, though not necessarily used:
- Davesgarden.com profile
- Mobot.org page for Ananas comosus var. variegatus
- Recommended: Water Roots profile of Ananas comosus
- Herself's Houston Garden
- (plus some of the sites listed in the bibliography for Part I)
Photo credits: my own, except as otherwise credited.
1 I was unable to find anything that identified 'Mongo' as to species; everybody just calls it 'Mongo.' It's most likely A. comosus, A. bracteatus, A. nanus, or a hybrid between two of those.
2 I know. Just roll with it, okay?
3 The actual suggestions: 68, 65, 60, 75, 60, 50 (F), which average out to 63F. Translated into metric, that's 20, 18, 16, 24, 16, and 10, with an average of 17C.
4 Semi-protected because you don't want the wind knocking your plant out of its pot before it gets a chance to root, and also because rabbits will eat the leaves, given the opportunity. I have proof:
5 Not fine sand. If the sand is too fine, it will compact around the roots over time, cutting off air. Coarse sand will do this too, to a degree, but larger particles don't pack together as efficiently, so you'll maintain a looser soil texture for a longer period.
6 Use your own judgment, but I'd say 2-4 inches (5-10 cm) is probably good enough to be potted up. Of course, I've failed at this every time I've tried it so far, so I don't know why you're listening to me in the first place.
7 Sadly, I am informed that the plant in the photo is no longer among us, having outgrown its indoor spot and moved outside. I don't have a good theory about why this happened, and as far as I know Matti and Megan don't either. If forced to guess, I'd want to know what sort of temperatures it was experiencing when it kicked, this being the only thing I can think of that could have gone wrong in San Francisco.
8 This also happens with avocados (Persea americana). People used to grow oranges, lemons, and other citrus fruit from seeds found in fruit, but I don't see people talking about it so much anymore. It may be that citrus seeds are harder to come by, now that seedless varieties are available for some species. Ginger (Zingiber officinale) and pomegranates (Punica granatum) are also occasionally done, but I would guess that they must not make especially satisfactory indoor plants or you'd hear more about it. (I've never spoken to anyone who said they'd personally grown ginger. I have talked, once, to a person who said she had an indoor pomegranate, but the context was that they'd called to ask us for help, because it was having problems. Which makes me think it may be uncommon because it doesn't usually work.)
9 For some bizarre reason, bromeliads are a tough sell to begin with. I don't understand why this is, but we had trouble selling them at work, or even getting anybody interested. When people were interested, they usually only listened until I got to the "and then after they flower, the main plant dies and produces offsets" part, after which they wanted to move on to look at something else. Doesn't matter that the dying might take two years or that the plant will produce its own replacements; once people hear "dies" it's all over, from a sales standpoint. Perhaps I should have been saying "dormant" or "sleepy" or something.