(click on the small photo to see it full-size)detailed discussions on separate pages are:
Tillandsias are a group of subtropical and tropical plants that grow naturally in a wide range of conditions—as might be expected when you consider they can be found at altitudes from sea-level to around 4000 meters. Not the same plants, of course! Geographically they range from Texas down to Chile. Yet despite the diversity of natural habitats, it is truly amazing how many different species will grow together in cultivation.
Tillandsias have evolved to inhabit extremely harsh environments. Because of this, they are resistant to adverse conditions and some can endure several years of total drought and temperatures at or below freezing provided they are not wet too long. Luckily for us, this hardiness translates to a ready adaption to growing in unnatural places such as the frost-free garden, the house, greenhouse or shadehouse. Tillandsias are often promoted as "air plants" which is true for most of them because they do take up their water and mineral requirements through their leaves, not their roots. But do not believe stories that they do not require watering. They are no different to any other living creature, they must maintain the water in their bodies or they die. They must be watered, but they do not tolerate being over watered. How much water they need depends on how dry the air is where they are growing (the "dryness" of air is not a simple relation to humidity. It is rather the capacity of the air to absorb moisture, which varies at various temperature/humidity combinations. For a discussion, click here).
Bright filtered light is the general rule, and the higher the humidity of the air the higher light will be tolerated. Outdoors the silvery-leafed varieties can usually be grown in full sun, but in an unshaded greenhouse or close to unshaded glass in a sunny room or conservatory the same plant will quickly burn because the air dries out like an oven. In these conditions of extreme drying, and consequent moisture loss, tillandsias cannot get replacement water from their roots like a terrestrial plant, or draw on internal reserves like a succulent. Outdoors you will never need to water a tillandsia hanging in a tree if you live in a temperate climate. Indoors, the hotter and drier the air, the more you need to water.
In the home or greenhouse, if you keep the tillandsias in an area with bright indirect sunlight and sufficient air circulation to keep the air from drying out, they should maintain their moisture if you mist them once or twice a week or submerge them for a couple of hours every two weeks during the warmer months. In a very sunny spot indoors they may need daily misting or weekly soaking depending on which method you prefer. Symptoms of under-watering are usually inward-curving leaves or leaf-tip dieback. When over-watered, the plant will rot and fall apart. No resuscitation!
A note on holiday care: DO NOT go away for a month and leave your tillandsias soaking in the bath! Leave them in a cool, relatively shaded place with no watering. They will survive for months without watering this way.
Never water tillandsias when the temperature is under 10oC or when temperatures are falling. If you do, you run the risk of the plants staying wet too long and rotting. They do not like being wet and cold for extended periods (weeks at a time) without drying out regularly. In cooler autumn and early spring months watering should be cut right back unless you are supplying night heating, or live where the night temperatures do not go below 15oC.
In nature tillandsias have a very slow growth rate and survive on very little moisture and nutrient intake. With good light and warm temperatures during the growing season they can be encouraged to speed up their growth significantly with heavy watering and weak fertilising (no more than 50% of the recommended rate for houseplants). But be very careful if you live in an area with cool winter nights - you must cut back the watering and fertilising from late summer/early autumn so that the plant's slow down before the winter.
Raising tillandsias from seed is a lot of fun, but you do need patience! For an introduction to seed-raising click here.
(click on the small photo to see it full-size)
These are all seedling plants from the same batch, Tillandsia stricta
X aeranthos. The top plant was grown in a different shade-house, with
automated watering which missed this plant. As a result of under-watering, the
leaves are curling inward to conserve moisture, the whole plant has shrivelled,
and the leaves are also starting to twist and die back from the tips. On
the bright side, because the dessicated plant has been growing in a cool
shade-house, it has lasted at least nine months without direct watering.
Two plants of Tillandsia balbisiana, both grown in our growing-on house. The plant on the left was hung high up, about 30cm from the roof, the other low down and shaded by other plants. Both plants received the same amount of water, but the one near the roof obviously dried out much quicker and again you see the leaves curling inward, twisting, and dying off from the tips - and from the number of dead leaf sheaths left on the plant, it has lost a lot of leaves (this is how they tend to look in their habitat, particularly during periods of drought). The larger plant, which has been able to absorb more moisture, is greener and fatter - but notice it also has leaf-tip dieback. I suspect this is a consequence of the plant coming from areas of high daytime humidity (low vapor pressure deficit) whereas our greenhouse is still relatively dry during the day.
This plant of Tillandsia plagiotropica shows the symptoms of a plant which really does not like dry air and high temperatures - even though it has been grown in a well-watered, moderately shady place in the growing-on house. There is no sun damage here, the air is just too dry and the leaves start to break down usually in the centre (A) - you can see a small dead patch which gradually encompasses the whole cross-section of a leaf (B) which then leaves the outer portion of the leaf to die off (C). We solve this problem by moving the plants out to a shadehouse, that is cooler and the air is not dried out as much as in an enclosed greenhouse.
1
2
3
This was definitely sun damage. Photo 1 shows a plant of a hybrid, Tillandsia AB92363 (very close to Tillandsia incarnata) in our growing-on house before the troubles. As you can see in photo 2, the whole side of the plant got burned out. It happened last winter (2000) where we had a protracted spell of fine sunny weather. Normally we water very early in the morning, but being winter we waited until the temperature had warmed up around midday. The plants were still very wet when the full sun can round early afternoon, particularly down in the leaf sheaths. The first symptom was a change in color of the leaf sheaths, followed by a collapse of the tissue in the leaf sheath then dying of the remainder of the leaf. In picture 3 you can see a normal leaf sheath, A, and a sheath burning out, B.
Over-watering is hard to detect before it is too late! These pictures show our two plants of Tillandsia sierra-juraezensis we imported. Not knowing what conditions the plants like, we put the larger, more healthy-looking plant in our nice warm growing-on house, and the other out in the shadehouse. Two years later, the cool shadehouse grown plant is on the left, the well-watered warm-grown one on the right. The warmer plant appeared to rot out from the centre, and we think this must have been because it was kept too wet. On seeing the damage, we dried the plant out in a cool,dark spot in the potting shed for a month, then out it out in the shadehouse. Luckily it has survived out there, so the rot cannot have got down to the growing centre of the plant.
Usually over-watered plants rot off in the centre, and give you few if any overt warning signs. The naturally curly-leafed plants, such as Tillandsia streptophylla, will usually give a clue by unfurling their leaves if they are getting too much water. Remember that when watering tillandsias their leaves should dry out within two to four hours, and they certainly should not stay wet overnight too often (preferably not at all in cool to moderate climates).
