Concerning airplants

[This essay is subject to change.]

There are many articles about airplants (Tillandsia spp.) out there. Many are based on years of experience with growing these fascinating and sometimes 
bizarre-looking plants. Some merely repeat what other articles say. Some have ideas that don't make a whole lot of sense. I'm going to repeat some of what is 
known from botanical studies, and debunk a few things about growing them.


Airplants are members of the plant genus Tillandsia, which is a genus in the plant family Bromeliaceae, known informally as bromeliads. They are perennial 
evergreen flowering plants that are epiphytes, meaning they grow on another plant, or some other substrate other than soil, and they derive their moisture and 
nutrients from the air and rain, or from debris accumulating around them. They absorb water from the air through trichomes, which are cells on the outsides of 
their leaves. They also absorb nutrients through their trichomes.  They have no roots, and stay in one place with anchors that look like roots. The anchors may 
be modified trichomes.

Wikipedia says: "They have naturally been established in diverse environments such as equatorial tropical rain forests, high elevation Andes mountains, rock 
dwelling (saxicolous) regions, and Louisiana swamps, such as Spanish moss (T. usneoides), a species that grows atop tree limbs. But there are also species that 
live lithophytic, so on rocks (but also roofs and even telephone wires).

"The green species with their claim to a cool-humid climate live mostly more in the shade terrestrial or in the lower levels of the forests. In contrast, 
almost all gray species live in precipitation-poor areas with high humidity. They prefer the full sun and can therefore be found in the upper floors of the 
woods, on rocks or (rarely) on the ground. Many of the gray species are epiphytes. Some species are more or less xeromorphic." -- wikipedia These paragraphs are 
apparently translations from German articles, and it might not be acceptable to transmogrify "the shade terrestrial" or "live lithophytic, so on rocks" into 
better English because I might change the original intended meaning. Thus, this essay, which was first intended to fix the wikipedia article but is now merely 
mine -- with my opinions. 

In Central Texas, where I live, ball moss is able to survive a month of drought during average daytime temperatures of 90F. This doesn't make them a kind of 
cactus. They are picking up dew in the early morning and soaking up as much water as possible in the occasional 30-second rain shower. The essential 
characteristic of airplants is that they dry out, then they get wet, and they dry out.

Kinds of airplants

There are an estimated 650 species of airplants. Wikipedia says they are native to the forests, mountains and deserts of northern Mexico and south-eastern 
United States, Mesoamerica and the Caribbean to mid Argentina. They are ecologically diverse: they are found in many different habitats and environments.  
However, all these environments must have one thing in common: occasionally they get wet.

As far as the actual taxonomy is concerned, there may be more than the estimated 650 species or fewer. The genus Tillandsia is incredibly diverse in 
appearance, size, and habitat.

I have two "T. ionantha" with completely different flowers. One has the blue spike that you will find by googling and the other put out a feathery structure. I 
doubt that they are the same species. Plants of the same species have flowers that look alike, so that a pollinator, pleased by a flower, will go to a similar 
flower. However, they were both sold as T. ionantha. One is the variety "Guatemala" and the other is "Fuego." The plants look similar (although "blue-spike" is 
greyer than the other), but not the flowers. The science of taxonomy relies on resemblances until more information is known. DNA testing will probably give us 
some answers. It may be that there is more than one genus of airplants, but only a cladistic analysis will tell us, and that might be a judgment call, anyway.

Wikipedia says that some airplants have a Crassulacean acid metabolism, but apparently some don't. This is enough to suggest to me that "standard rules" for 
growing airplants might not always be good rules, and moreover, that the genus Tillandsia should probably be divided into two or more genera.  This kind of 
metabolism is used by plants adapted to an arid environment, but it is also used by some wetland plants ("hydrophytes"). I am not going to explain what a 
Crassulacean acid metabolism is, so look it up.

In any event, there are many kinds. The commercially available ones are the easiest to grow, undoubtedly. If you bring home (smuggle) an airplant from your 
tropical vacation, try to give it a place like the place where you found it. The best way to grow an airplant is to imitate its natural environment as much as 
you can. If it was growing on a branch, or a rock, or upon dry sand, try to give it a similar home.

Life Cycle

A healthy airplant appears to be doing not much of anything. It doesn't get noticeably bigger once it's reached a certain size. It may turn a greener color 
over a period of several months or a year. This may be the only sign that it is growing. Suddenly, it puts out a flower, which may persist for some time, then 
it makes offsets a.k.a "pups": smaller versions of itself attached to the parent plant. The parent plant, having used up all its resources and provided for the 
next generation, then dies. The time from flowering to the death of the parent plant may be months. The offsets repeat the cycle, and eventually a "cluster" of 
airplants may form.

What is going on here? Presumably, although the parent plant is not increasing in size, or it is growing so slowly that it's unnoticeable, it is slowly storing 
up energy during this time for the big moment when it flowers. If botanists have studied what is stored and where it is stored, I don't know about it. However, 
the Crassulacean acid metabolism, also called the C4 cycle, works by storing carbon dioxide in the form of malate to be used later.

Note that airplants have both sexual reproduction (flowering) and asexual or vegetative reproduction (making offsets). This raises some interesting ecological 
questions, such as: why do they use both kinds of reproduction? Is it because the chances of successful pollination are low? Do they produce much nectar, or 
are pollinators attracted by the colors of the flowers? Do all the airplants of a species in a certain area flower at the same time, so they maximize the 
chances of getting pollinated? (That is what most plants do, but they follow the seasons. It is known that all the plants in a "cluster" may flower at the same 
time.)  Does anyone know the answers?

What is known: flowers are visited by moths, hummingbirds and sometimes bats. Obviously this isn't going to happen indoors.  An airplant cannot pollinate 


Many airplants are adapted for an arid environment, or an environment with only occasional rain. This is presumably why they have no roots to extract water 
from the ground. In fact, they will rot and die (like a cactus that is over-watered) if they are planted in soil like most plants. They generally grow on tree 
branches, rocks, or wherever they can, such as roofs and telephone wires. Desert species may grow on the ground if it is dry, it seems, but I haven't seen it.

Airplants need air. They need it for two reasons:

1) To dry out after they get wet. This is not a problem outside where they are exposed to the wind, but indoors, where the air is not moving, it can be an 
issue. Placing them by an open window is not always practical, nor is using an electric fan.

2) Air contains nutrients. Dust is made of tiny particles of many things: soil, plant matter, feces, and everything else that is in the environment but usually 
comes in bigger pieces. There is much less exposure to wind-blown dust indoors, and you should use a fertilizer.

Things you read about airplants

1. Airplants in general do not like direct sunlight.

In nature, they usually grow on branches of trees, where they are shaded by the leaves of the trees from direct sun. As in all things, there are exceptions. 
"Ball moss", common in the southern USA, will tolerate direct sun (at least for part of a day) and has been seen growing on telephone wires. Ball moss also 
grows on deciduous trees and may be exposed to full winter sun for a couple of months a year. It's doubtful that it could stand direct summer sun, though.

There are tropical species that grow on rocks, but maybe these are only found on the partly shaded parts of rocks; I have not read anything about that. There 
are ones that grow in deserts. But for the common species that you are likely to buy (the ones bred commercially) such as T. ionantha, T. bulbosa, etc. this 
rule holds true.

As far as I can tell, all airplants grow well under artificial light. LED grow lights might be best, but some people grow them in places where there is no 
regular source of light; e. g. on the refrigerator or in the bathroom. I am not sure how well that works.

2. Airplants are hard to grow.

This statement, I think, has been made by people who treated an airplant like an ordinary plant. You can't grow them in dirt, you can't keep them wet, and you 
do not have to worry if they dry out. Airplants don't show any signs of wilt when they dry out, and if you allow them to stay wet, they will rot and die before 
you realize what's happening.

In nature, they depend on rainfall and dew. They may get only intermittent rainfall and they do not have roots to extract water from the soil. In the tropics, 
in the dry season, they may go for a month without any rain. In the rainy season, they may get rain every day, but they are built to shed excess water, which 
then runs off the branch or wherever they sit. And the rainy season in the tropics does not mean constant rain; it usually rains every day, but not all day. 
This gives the plant a chance to dry out.

Most important, I think, is growing them on the right medium: a piece of natural wood, a porous rock (such as limestone), a bed of small rocks with drainage 
(probably not small gravel or sand, because it might hold water), a the convex side of a piece of unglazed clay pot, or any other substrate that allows water 
to be drawn from the plant and then evaporate or drain away. You can string wires across a window and grow them there, although that is not very attractive.

The practice of growing an airplant in a glass bulb or a seashell is dangerous in my opinion, because water can accumulate unseen inside the glass bulb, under 
the plant, and before you know it, it's dying. The glass container may be open to the air but a little water built up in the bottom can cause a problem. I do 
not recommend any kind of non-porous surface as a place to grow your airplant, unless it is slanted to allow water to run off easily. For instance, roofs are 
not porous, but airplants have been seen growing on roofs.

However, you also have to consider that airplants have to hold on to the substrate. That makes natural wood and porous rocks your best bets. The piece of 
unglazed clay pot might work, but the pups might not be able to hold on.

Watering Airplants

There are two ways to water airplants: soaking and misting. Either way, the plant must dry out completely before you water again.

One thing that is said by some growers is not to use distilled water. They then go on to tell you to use rainwater. Distilled water is as close to rainwater as 
you can get, without actually collecting rainwater, so that makes little sense. Then they say that if you do not have rainwater, use tap water. Do not use tap 
water because it contains 1) chlorine or fluorine compounds, added by your water utility for bacterial control and for your teeth, and may contain 2) calcium 
carbonate, found in "hard water," which is essentially dissolved limestone, and may contain 3) impurities such as lead (which is not good for you, either) or 
4) water softeners so washing machines work more effectively, and whatever else your local water supply adds to your water.

Furthermore, if you mist your plants, the stuff in the tap water will clog up your mister.  If you live in a place like Austin, Texas, where the showerhead 
gets clogged up and you have to take it apart and remove limestone rocks from it, don't put that water on your plants. That goes for all plants, not just 

Purified tap water, with one of the filters that you can buy to make your water suitable for drinking, should be OK. You want to avoid any buildup of calcium 
carbonate or metals on the leaves of the plant. It is my understanding that these filters remove large ions of that kind. I use distilled water for all my 
plants: airplants, herbs and decorative plants, because any kind of impurity in the water will accumulate. You will eventually see the residue on the pot in 
which the plant grows.

It is said by the persons who suggest tap water that it contains nutrients. It doesn't. Plants, including airplants, do NOT acquire any nutrients from tap 
water. All a plant wants is pure H2O. If you are serious about growing plants, get a machine that distills water.

However, if you live in a rural area and have clear-running creek water, and you are sure that it contains no dissolved metals, and it isn't of a limestone 
origin (check the pH, it should be between 6 and 7) you can use that. It probably contains some micro-organisms that will fertilize your plants. Rainwater 
might also contain some tiny critters or algae that will be fertilizer. More about fertilizing later.

Most articles about airplants suggest that you soak them in a bowl of water. This is not what happens to them in nature, although it's probably similar to a 
heavy rain. The only caveat, again, is make sure that the plant dries out completely before soaking again. Soaking twice a week or less frequently should be 

Misting is my preferred method. I don't have to move the plant or have it sit in water where I might forget about it. I got a nice brass mister for $20 through 
Walmart. Every two or three days, I spray my plants until they are wet. A single squirt won't do it. Get them wet, and then let them dry. That's the way they 
live in nature.

If you keep your airplants outside, I see no reason why you can't take a suitable amount of good water and pour it over them every few days, if it hasn't 


The humidity that an airplant prefers depends somewhat on the species. Although airplants have evolved to live in an arid environment, they are not cactus. 
Direct sun and low humidity will kill them just as surely as being wet all the time.

Because airplants do not get water through their roots, because they have no roots, they get water from the air, usually from rain. Wikipedia says they close 
their stomata (the openings through which they breathe) during the day to prevent water loss.  They open them at night to fix carbon dioxide and release oxygen 
(which is normal for plants).  "This allows them to preserve water, necessary because they are epiphytes." – wikipedia. All plants can close stomata to keep 
water from escaping. But because airplants have only intermittent water and can't get it from the ground, they may depend on ambient humidity to maintain their 
water balance when they open their stomata at night. However, because they are adapted to an arid way of life, they are not really fussy. High humidity is bad; 
they will not dry out and they will rot.

If they are put in a very dry environment (such as one with constant air conditioning) they may fail. I think that if you run the AC constantly, you should 
mist lightly every day. Even species that prefer an environment without much rain, which is most of them, still like some humidity. Always make sure your plant 
dries out between waterings. If in doubt, don't water. And don't put it where the dry air from the AC blows on it. The presence of other plants is probably 
beneficial, because they will help maintain a constant humidity.


Although airplants are considered to be "tropical" plants, that doesn't mean they need a greenhouse with high temperature and humidity. I have known commercial 
bromeliad growers and compared to what they have to do with temperature (and they have to maintain a certain humidity level, too), it's easy to grow airplants. 
(It may surprise you to learn that there are bromeliads and orchids that grow in desert environments, just like airplants.) The bottom line is that any 
temperature that's comfortable for you, say, 65F to 75F, is fine for your airplants.

If you keep them outside, bring them in if the forecast says the temperature will go below 50F. That is about their bottom limit. As always, there are 
exceptions: T. usneoides, known commonly as Spanish moss, can tolerate frosts down to about -10°C. It is likely that T. recurvata, its close relative, known as 
ball moss, has a similar tolerance to low temperatures. Neither of these plants are very colorful and I don't know anyone who grows them. I admit I have 
considered it myself. It would be easy enough to get a fallen branch with one of these species on it, and zip-tie it in a suitable place.

Airplants should not be allowed to heat up in the summer sun. They do not like continual sunlight at all. This is why I am not sure about how desert airplants 
grow, because one pictures a desert as a wide flat area without shade. "In contrast, almost all gray species live in precipitation-poor areas with high 
humidity. They prefer the full sun and can therefore be found in the upper floors of the woods, on rocks or (rarely) on the ground. Many of the gray species 
are epiphytes." – wikipedia.  The literature says their top temperature is 90F. Probably they can withstand that temperature in the shade, with misting.

Indoor temperatures, the ones you like, are ideal.


I have been using a commercial fertilizer that comes in a spray bottle that says it has a 20-10-20 ratio.  This is the Nitrogen-Phosphorus-Potassium ratio. It 
claims to be "urea nitrogen" free, boron free, dye free, copper free, and zinc free.

All this is very well except the "urea nitrogen free" because urea is probably a common natural source of nitrogen for an air plant. Perhaps the intention is 
to make their product sound like it is vegetarian and no one pissed in it. I have no idea. As for dye, yes, of course. However, all living things need boron, 
copper and zinc in trace amounts; they are called "essential micronutrients." They are all probably present in trace quantities in the air. It is somewhat 
troubling that the label of this fertilizer brags about not containing these elements, but of course plants can get too much of them and be poisoned.

Commercial spray fertilizers, like that one, are surely good enough.  The air itself supplies other nutrients. Airplants in your house obtain others by chance: 
the stray cockroach, the smell of chicken soup, a sneeze. The natural environment contains tiny animals that contribute, as I say below.


I grow airplants in a terrarium. Many people say not to do this. They are right, if you do it wrong. Let me explain how to do it.

1. No circulating air.
2. Too wet.


1. Use an aquarium air pump to supply a constant source of air. You can get a quiet one for less than $10. You need some tubing, which is usually sold 

2. Do not overwater. If you see condensation on the sides of the terrarium, remove the top or put it askew so air circulates, and let it dry out. Originally, 
my terrarium was a swamp and I had to dry it out. Now, I can add a bit of extra water (an ounce at a time) for the lichens and ground cover. (I still grow 
water plants and wetland plants, but not in the airplant enclosure.)

The basic routine is to let the terrarium alone for 2 to 4 days, and then water. Watering consists of misting the airplants heavily, and pouring a little water 
on the lichens and ground cover. I leave the top of the terrarium askew so that I can put the grow lights on top with more ventilation. After I put the top on 
straight, if I see condensation on the sides of the terrarium after a while, it is too wet. Then I have to put the top on crooked again.


1. Constant, or nearly constant, humidity and temperature. Put the airplants on rocks or small logs, and have a ground cover and perhaps an area or areas in 
which small terrarium plants live. It depends on the size of the terrarium. A suitable drought-resistant ground cover is Dichondra. You can look around and see 
what weeds grow as ground cover (often in the sidewalk cracks) in your area. You need drought-resistant plants because they are only going to be sprayed with 
water and maybe get a small drink now and then. The presence of other kinds of plants helps to stabilize the whole environment, including humidity. Remember 
that airplants naturally live on and with other plants. Make this like a standard terrarium, with a bottom layer of charcoal, a layer of gravel, then a layer 
of soil, and the rocks and wood for the airplants on top. The mass of soil, gravel, rocks and wood retains heat and helps to prevent sudden temperature 

In the alternative, I suppose, you can grow terrarium plants that require water and water them well and just mist the airplants lightly or hardly at all. I 
haven't tried this.

2. Environment. By putting your airplants in a more natural environment, you can make them more attractive, and give them natural fertilizer.

The idea is to have ordinary dirt with some plants, some rocks, some rotting pieces of wood, and an entire arid ecology. Try to get pieces of wood with 
lichens. Lichens, although very different from vascular plants, live similarly to airplants – they like to be watered and then they dry out. They can be white, 
yellow, orange, etc., all the way to purple, and they will make your terrarium more colorful. But the airplants are the stars of the show. When another plant 
gets too large (like my horseherb does) cut it back mercilessly.

Living in ordinary dirt there are thousands of critters per cubic foot called springtails (Collembola). They are beneficial for a terrarium, because they eat 
waste products and fungus but not plants. You can learn about them online and order them, and learn how to maintain a population of them. You shouldn't have to 
order them, though; just go out and collect some moist soil and scatter it around the terrarium. (You are very unlikely to get anything that will eat an 
airplant.) Springtails like rotting wood and the wet places under rocks. They are attracted to water. When you spray your airplants, they will go to the water, 
shed their skins, leave their droppings, and generally provide natural fertilizer.

Imagine for a minute what it's like for an airplant growing in a forest in Guatemala. It might be bombarded at any minute by the excreta of a bird or some 
other animal. (Not a sloth, because sloths descend from the trees every few days and bury their droppings in the ground, but that's not important right now.) 
This is excellent fertilizer but it will take several rains to wash it away. The airplants you might be growing work on a smaller scale: bug droppings and shed 
skins are enough. Get a liquid fertilizer to spray once a month when you water.

3. Beauty. You can arrange the terrarium. Make your airplant terrarium beautiful. Make it artistic. Airplants are easy to move if they haven't attached 
strongly to a substrate. I knocked one over by accident and it landed upright in another place, and did fine.

The airplants are the star of the show. A single airplant on the door of your refrigerator is not nearly as nice.