Air plants or, more correctly, tillandsias (Tillandsia spp.) are currently very popular. They are called “air plants” because in nature they live suspended on branches or even electric wires, without soil, apparently living only on air. They are indeed very attractive plants and seem to do well at first when you bring them home, but rarely survive a year in the average home. Your air plant has in fact probably been slowly dying from the minute you brought it home.
In spite of this, typical garden centers that sell tillandsias continue to insist that they are “easy to grow”, as if the fact that 99% of those sold don’t survive was if little importance. Why? Because their definition of “surviving” is not the same as yours.
In the indoor plant industry, the accepted policy is that a houseplant is supposed to survive 8 weeks. If it lives that long, then you, the customer, got your money’s worth. (Read The Life Expectancy of Houseplants for more details.) After that time, sellers presume your plant will be so degraded that it will be time for you to return to the store to buy a replacement.
The result is they give you enough information for the plant to live for a while, but don’t tell you how to truly grow tillandsias so that they’ll really live a full life and come to bloom. I’ll try to do that in this article.
Not Like Other Houseplants
Growing tillandsias is very different from other houseplants (note: this article concerns only the cultivation of tillandsias indoors in a temperate climate, not raising them outdoors in the tropics, which is a very, very different subject). If you treat a tillandsia as a typical houseplant, you really will kill it. It needs its own special care… but first, let’s look at what are air plants are.
Defining Our Subject
The New World genus Tillandsia belongs to the pineapple or Bromeliaceae family. The genus is vast, with some 730 species, and present almost everywhere in South and Central America, even as far north as Virginia in the United States.
The vast majority of the species are epiphytic: that is, they grow on other plants, especially on the branches or trunks of trees. Even though South Americans often call them “parasitos”, they are not parasites and do not harm their host. They simply grow on them, taking nothing from them but support. Not all tillandsias are epiphytes, though: some species are terrestrial or live on rocks or cliffs.
The tillandsias are variable in form, but always have lanceolate leaves that grow in a spiral. Some have visible stems, but most are stemless, forming a rosette, much like an aloe plant. Others bear only a few well-spaced leaves and can look like an octopus.
Moist or Dry
Tillandsias are often divided into two groups, mesic and xeric.
Mesic (medium humidity) tillandsias grow in rainforests or in shade, where the air is always moderately humid. These tillandsias are have green leaves with little in the way of gray markings. The leaves tend to be thin and pliable. Some have “tanks”: a central cup formed by their leaves that captures water and these get most of their moisture from this tank. Others though have no tank and absorb water through their foliage.
Most mesic tillandsias have the ability to produce “normal” roots, that is roots that are long, abundant and good at absorbing water, if they are planted in potting mix. This is a sharp contrast to differ to xeric tillandsias, most of which have lost that ability.
Xeric (low humidity) tillandsias are the ones most gardeners consider air plants. They are extreme epiphytes and don’t have much of a root system other than a few tough-as-nails anchor roots. They don’t have a tank. Some grow in deserts, sometimes as epiphytes on cacti, but most are native to either dry tropical forests or exposed spots in more humid climates.
With no roots worth speaking of, xeric tillandsias absorb all the water necessary for their survival from their leaves, through rain, dew, or even atmospheric moisture. Curiously, these plants will often grow upside down and this habit is sometimes repeated indoors indoors to create unique effects.
The foliage of xeric tillandsias is at least slightly greyish, if not out-and-out silvery, as it is covered with whitish scales called trichomes. These trichomes have the ability to absorb the water and minerals their roots can’t. A freshly watered xeric tillandsia will appear almost green, as trichomes become translucent when loaded with water, but will resume its gray-green color when the water is absorbed by underlying cells.
And the roots in all this? As mentioned, in xeric tillandsias, they don’t absorb water and minerals like normal roots do, but instead simply anchor the plant to its support. They are small and few in number, even absent in one well-known species, Spanish moss (T. usneoides).
Should Air Plants Be Mounted or Not?
Attaching xeric tillandsias to a support isn’t absolutely necessary. You can simply place them on a shelf or on a decorative plate and they will continue to grow and thrive.
Nowadays, stylists often insert xeric tillandsias into glass globes, among colored dried stones or lichens, without fixing them to anything. That way they can be removed for watering purposes.
Other vendors insert them into shells or small pots, again without mounting them. You can do the same with the pot of your choice. Just fill it with orchid growing mix (a very aerated growing mix), sphagnum moss, stones or even gravel, but never potting soil for indoor plants, which is far too dense and humid. And there is no need to water chosen substrate.
You can however mount them if you want, that is, permanently glue them to a support, a piece of wood, a rock or any other decorative object. This is done when the object chosen has no hole in which you could insert the tillandsia.
Do this using a fast-drying liquid glue such as Liquid Nails or Goop, a hot glue gun (no, it does not heat enough to burn them) or even silicone sealant. You may need to use a bit of wire to hold the plant in the right position while the glue dries. Only add a drop to the plant’s base and try not to cover the roots: if it’s a young plant, they may still grow and fix themselves to the support. Note that it is by the base of the plant that you have to mount it, not by its lower leaves, as older leaves will eventually die, causing your plant to come loose.
To hide the glue at the plant’s base, you could apply a little sphagnum or dry moss to the glue before it dries, but not too much, because moss holds water and you don’t want the base of the plant to remain moist for any lengthy period.
You can also mount xeric tillandsias with monofilament fishing line.
Growing Air Plants
Non-specialist sellers of xeric tillandsias, like garden centers, often suggest a location “in bright light with no direct sunlight”… and that results in their slow death from lack of light. They picked up this information from tillandsia growers in the deep tropics where full sun is indeed very intense. In northern regions, however, direct sunlight, at least a few hours a day, is absolutely necessary if you want to keep xeric bromeliads growing over the long term. A window facing east, south or west would be suitable. During the winter, even give them full sun if you can.
Xeric tillandsias can also be grown under intense fluorescent or LED lamps, placing them no more than 30 cm below the lamp. This is the ideal situation if you’re growing them in a terrarium.
Since xeric tillandsias don’t absorb water through their roots, you’ll have to water them through their leaves… and this causes a problem for the home gardener, because it is also through their leaves that they carry out respiration. If their leaves are always covered in moisture, they won’t be able to “breathe”. So you’ll have to moisten the foliage, but also, let it dry out thoroughly if you want to see your tillandsia succeed.
The most effective technique for watering a tillandsia is to plunge it into lukewarm to room temperature water. Remove the plant from its support and hold it under water for an hour or so or dunk the whole support into a bucket or container of water. Afterwards, turn the plant upside down and shake it to remove any excess moisture: you don’t want any water to remain in the crown. Normally, a good “soak” once a week will suffice for species with very silvery or greyish foliage. For more mesic types, with green foliage, two or three weekly soakings are sometimes necessary.
You can also do a quick dunk, just plunging the plant into water for a few seconds, then shaking excess water free, but in that case, you may have to repeat the dunking several times a week. Even if you’re into “quick dunking”, it’s best to let the plant soak at least once a month, just to make sure it’s getting the water it needs. If you see the leaf margins curling in towards the center, that’s a sign the plant is dehydrated and needs more water.
Obviously, if your tillandsia is mounted on a large support, you won’t be able to soak it in water. You’ll have little choice but to mist it with lukewarm water… and that’s a bit of a challenge.
Spray it until saturation, that is until excess water drips down, then to repeat 15 to 20 minutes later: a single misting is rarely enough to rehydrate the plant correctly. Since misting tends to keep the plant constantly on the verge of dehydration, you should repeat 2 or 3 times a week, even more if the air of your home is very dry.
No matter what watering method you choose, it’s best to water in the morning so the plants will have the time to dry out before nightfll. The foliage must be dry at night, as tillandsias carry out CAM photosynthesis (delayed respiration): unlike most other plants, they only carry out respiration at night.
Just a quick word about mesic tillandsias grown in pots. No, these aren’t air plants, but still appreciate it if you spray their foliage with water. Still, fill their tanks with water as well (if they have one) and also water their growing mix, as they do have water-absorbing roots.
Warning! Tillandsias sometimes react badly to tap water, often too alkaline and or too mineralized for their taste, especially over time. Alkaline well water is no better. It’s best to use rainwater or bottled water.
If you water by soaking or dunking them, just leave a container of rain or bottled water near where you grow them, then seal it with a cover after you’ve finished. That why you can use the same water over and over again without constantly having to get a fresh supply.
Xeric tillandsias don’t need much fertilizer. They’ve adapted to an extreme environment where there is little available in the way of minerals other than dust and a bit of nitrogen from rainfall. At the Montreal Botanical Garden, for example, which maintains a good collection of tillandsias, they never fertilize their tillandsias at all! If you want to “feed” yours, wait a year (to be certain that you have learned the basics of their care), then add a little of fertilizer to their water (no more than a quarter of the recommended dose) before you soak, dunk or spray them.
Lacking roots, tillandsias don’t have the ability to absorb urea nitrogen, the usual source of nitrogen in fertilizer. You’ll have to look for a fertilizer that includes nitrate or ammoniacal nitrogen, such as an orchid or epiphyte fertilizer.
All tillandsias like moist air, even the most xeric ones, and most homes need a humidity boost I order to keep them happy, especially during the winter months, because heating a house lowers its relative humidity. Here are some suggestions for maintaining good atmospheric humidity: High Humidity = Happy Houseplants.
The tillandsias depend on good ventilation more than just about any other houseplant and indeed count on it to help them dry out after watering. That’s one reason they love to spend the summer outdoors: there is always moving air (more on that later). From spring to fall, placing your plants near a window that is often open helps a lot, but it’s hard to ensure good ventilation during the winter when all the windows are closed. You might want to run a small fan in the room, although not pointing directly at their leaves (that could dry them out excessively). Indoors during the winter, at least give them some room (i.e. don’t crowd them with other plants) to allow a bit of air movement.
Growers of tillandsias as houseplants rarely have to take this factor into consideration. Any indoor temperature between 10˚C and 30˚C will be suitable.
Tillandsias probably profit more from a summer outdoors than any other plant. It is often at this time of year that they put on all their growth for the year; when left indoors, they may cease to grow entirely. Put them in the shade when you first move them out, then gradually acclimate them to part shade with a few hours of sun or even full sun. Obviously, a spot with good air circulation will do them the greatest good and they also appreciate the rain that usually brings what little fertilizer they need. Also, growing them outdoors cuts way back on their care. In humid climates with regular rainfall, they’ll need no care whatsoever while they’re outside. In drier climates, water them once or twice a week. Just soaking them with spray from a hose is all the watering they’ll need.
Tillandsias in Terrariums
That tillandsias can be seen in terrariums, especially the small glass globes found in just about every garden center, is proof of their great ability to survive appalling conditions, because they hate terrariums, especially when you follow the vendor’s advice and water them by spraying water directly into the container. Even in the store, tillandsias seen in terrariums are often already dying or dead… and you can’t revive a dead plant.
Why are terrariums a problem?
First of all, it’s hard to give the plant adequate lighting when you grow it in a glass container. If you place it near a window, where they really prefer to be, the greenhouse effect of being nearly surrounded by glass causes heat to build up, often with fatal results. Yet if you move them away from the window, they suffer from lack of light. Doubly so, since each layer of glass cuts out even more light. The ideal situation for a viable tillandsia terrarium is under artificial lights, which at least don’t heat up excessively. An east window, cooler than south or west exposures, may also work.
Secondly, tillandsias, which love good air circulation, receive almost none in a globe with a single opening or an open-top terrarium with four glass sides. If you want to create fairly happy tillandsia garden in a glass globe, at least look for one with two openings, one on either side, to allow for air movement! If you’re thinking about putting tillandsias in a closed terrarium, limit your choice to mesic tillandsias, those with green leaves, more able to withstand the high humidity and poor air circulation that reigns there.
The best way to water a tillandsia in a terrarium is to take it out and soak it. And don’t put it back into the container until the foliage is completely dry, which can take up to 4 hours.
Many tillandsias change color when flowering approaches: this is called blushing. The central leaves turn red, if not the whole plant. In nature, this coloring helps attract their main pollinator, the hummingbird. Some species produce an extended flower stem from their center with red, pink or yellow bracts, but in others flowers emerge directly from the rosette. The tubular 3-petaled flowers are usually violet.
Each plant blooms only once, then dies. (It is said to be monocarpic). Before dying, however, it produces one to many pups. The “mother” doesn’t die overnight, though: it remains alive for months, feeding her pups, until they’re mature enough to survive on their own.
That said, conditions in many homes are not conducive to flowering. The plant can therefore live for years, changing little in appearance, without any flowers appearing. If you think your plant is mature and in good shape, you can “force” it to bloom by placing it in a plastic bag with a mature apple (a source of ethylene, a toxic gas) for a week. (Avoid full sunlight during this treatment). The plant, threatened by toxic air, will bloom one or two months later in an effort to reproduce itself.
Often tillandsia growers spray them with non-toxic paint to improve sales. This is called, believe it or not, “enhancing”! They claim this treatment doesn’t harm the plant. Under ideal conditions, that may be true, but few tillandsias live under ideal conditions in our homes and a coating of paint, which reduces its capacity to absorb both light and water, hastens their death. Before you buy any tillandsia, ask to be pointed to one that has not been “enhanced”.
Normally you multiply tillandsias by removing pups (offsets), and most only pup after the flower, Even though some species do start to produce pups before they bloom, the pups tend not to develop until after flowering. When the pups reach about 2/3 of the size of mother plant, you can safely separate them and use them as you see fit. Expert growers will harvest them at an even younger stage, but that is risky for the home gardener.
After flowering, tillandsias will also produce seeds with a silky parachute that blow in the wind… outdoors. If you catch and sow them, they will give you very tiny plants that will need a lot of pampering to mature. Still, it will give you lots of tillandsias to trade!
To Sum Up
Does the above mean that tillandsias are not good plants for laidback gardeners? Not at all… if you have the right conditions. After all, soaking a plant once a week is no more difficult than watering it with a conventional watering can. But what should not be done with a xeric tillandsia, cultivated without potting soil, is to treat it “like just another house plant”. It is not your usual houseplant and will always need special care.