air plants

Living From the Air

Air plants, air ferns, oxygen plants, tillandsias, Spanish moss, old man’s beard, air bromeliad…

These are all names commonly used for air plants, members of the genus Tillandsia. This is a genus of plants not always well understood by people, but one that is always intriguing.

What are air plants?

Air plants are members of the genus Tillandsia, which in turn forms part of the bromeliad or pineapple-plant family. They grow on trees where they attach themselves to branches and can often be seen hanging from trees, seemingly living from the air – hence the name. Not all tillandsias are air plants though, as some prefer to have their roots growing in moss or leaf litter and not exposed on the branches of trees.

Are air plants and air ferns the same?

Although some people refer to certain tillandsias as air ferns, this is not correct. The term is more commonly used for a member of the genus Sertularia. Sertularia is not a real fern – in fact, it is not even a plant. Sertularia is related to corals and jellyfish, and the ‘plants’ are collected by trawlers. The animals are then dried and often dyed green, to be sold as low-maintenance ‘house plants’. (They were very popular in the 80s.) Because they are not alive they need no maintenance, water or light.

Where do air plants come from?

The members of the genus Tillandsia are naturally found in a range from the southern parts of North America through Mexico and Central America and into South America, with Argentina being the southernmost point of distribution. Some species can be found in the Caribbean as well.

Different species (there are approximately 650) can be found growing in different areas with varying habitats. Tillandsias are not native to South Africa, although the old man’s beard lichen found along the mist-belt is often confused with tillandsias.

How do air plants grow?

In their home ranges most air plants grow by attaching their roots to the bark of trees. This can be on the main stem, larger branches or even thin twigs. In the case of Tillandsia usneoides (Spanish moss) the clump of plants just hangs from the branches and doesn’t actually grow onto the bark. There are a few species that can be found growing in the sand dunes of the Peruvian desert as well.

Do they live on air alone?

Contrary to popular belief, air plants actually need moisture and nutrients to grow properly and don’t live on air alone. They are not able to ‘extract moisture from the air’ as is often believed. The exact same thing that gives most air plants their silver-grey appearance is what allows the plant to survive growing ‘in the air’. The whole plant is covered with tiny scales that can catch any bit of dew that might settle on the plant. It is also useful in expanding the surface area of the plant to allow for a bigger area on which moisture can collect as condensation. The water is then absorbed either through the leaves or channelled to the roots for absorption along the leaves or the base of the plant.

Those species found growing in the Peruvian desert do not receive any actual rain during the year, surviving only on the moisture they get from the mists coming in from the ocean and condensing on the leaves. If they don’t survive on air, are they parasites? It’s often believed that a plant that grows on another plant must be parasitic. This is not the case, and in fact most plants that grow in this manner are not parasites.

A plant that uses another plant as support but does not get water, nutrients or sugars from the host plant is called an epiphyte, and air plants form part of this group. Air plants may grow on a wide range of different hosts, depending on the habitat, such as trees, shrubs and even cacti. They will also grow on dead wood as they do not need their host to be alive. Certain tillandsia species prefer growing on rocks or cliffs. Plants that grow on rocks are called saxicoles.

But do they flower?

The simple answer would be yes, but not everything in life is simple. Yes, they do flower in order to produce seed, as most plants do, but as there are so many different species of air plants originating from an array of different habitats, they do not all flower in the same conditions. Those species from the Peruvian desert seem to get more moisture from mist during the winter months, which results in a climate very similar to the Mediterranean or Western Cape with a winter rainfall. This means that these species do not flower in the summer-rainfall areas of our country, or if they do it is the exception to the rule. Even Spanish moss (Tillandsia usneoides) flowers, the flowers are just very small and sort of aquamarine in colour and so are often overlooked.

Many air plants have got quite showy bracts covering the inflorescences with a contrasting flower colour. In their natural habitat, these flowers are a source of nectar for many a hummingbird and other birds and insects.

Do air plants die after flowering?

As air plants form part of the bromeliad family, the main concept is the same. A plant will flower when mature (the time to maturity will depend on the species), produce seed and then produce side shoots or pups before dying. The pups will then mature and flower, and so the cycle continues. There are a few species of tillandsia that are considered to be monocarpic, which means the plant will not produce side shoots and pups but just seed as a form of reproduction, but these are in the minority.

If air plants grow on trees, are they related to orchids?

Tillandsias and orchids are not related. They have evolved a similar habit of growing and can often be found growing in the same conditions, side-by-side, but they are not related. In the following two articles, we will take a closer look at the different types of air plants, both species and hybrids, and how to grow them and care for them.

The Gardener