It's all up in the air for epiphytes

Drinks? Dinner? Romance? It's all up in the air - if you're an epiphyte. Wait...a what?

Epiphytes are plants that grow upon other plants. Most plants we know have roots that reach down into the soil to absorb water and nutrients. Since epiphytes are up in the trees, they can't do that. They have evolved to get their water and nutrition from whatever blows in on the breeze. And, many epiphytes count on the wind to disperse their seeds or spores. It's all up in the air for epiphytes.

Epiphytes would want you to know they are not parasites. They just use the host plant for physical support, and usually don't cause any harm. As a nice community service, they provide food and shelter for small animals and tree frogs.

In south Florida, there are three main types of epiphytes: orchids, bromeliads and ferns. Not all species of these plants are epiphytic, but many of them are, and each has its own way of successfully living up in the trees.

Florida's three main types of epiphytes (from left to right): orchids, bromeliads, ferns.

Florida's three main types of epiphytes (from left to right): orchids, bromeliads, ferns.

Orchids

Everybody loves orchids, so let's start with those. There are around 20,000 orchid species in the world. The tropical ones usually grow as epiphytes. In Florida, we have 100 native species of orchids, and the Everglades is the best place to look for many of them because of the cloyingly hot, moist climate orchids love.

Untitled photo

Of course, orchids are best known for their beautiful flowers. You might look at the especially intricate shape of orchids' flowers and think to yourself, "gee, it looks like that flower was built for a very specialized means of pollination." You would be right - at least most of the time! Some orchids can self-pollinate, but most orchids' fancy flowers are the result of co-evolution between a specific species of orchid and a specific species of pollinator - usually an insect. Insects who land on the wrong type of orchid would be disappointed - and perhaps embarrassed - as they try unsuccessfully to get to the nectar.

This orchid is commonly called "Ladies' slippers." Its complex shape attracts a certain type of insect - and makes it impossible for other insects to drink its nectar or pick up its pollen. If we were to put this on a tree in south Florida, it would survive, but wouldn't be able to reproduce because its pollinators don't live here.

This orchid is commonly called "Ladies' slippers." Its complex shape attracts a certain type of insect - and makes it impossible for other insects to drink its nectar or pick up its pollen. If we were to put this on a tree in south Florida, it would survive, but wouldn't be able to reproduce because its pollinators don't live here.

Both parties benefit from this arrangement. The insect benefits because it doesn't have to compete with other bug species or expend precious energy flying to flowers that don't offer them the specific brand of sugary nectar they crave. The orchid benefits because the insect will only carry its pollen to another orchid of the same species, which helps the orchids reproduce more efficiently. Most of the time, this arrangement works out great. On the other hand, the orchid and insect are also completely dependent on each other for survival. If disease or bad weather kills off one or the other, there's no back-up plan.

In spite of their tropical habitat, orchids are adapted to drought! Why? Because when rain is not falling, air and the bark of the host tree could pull water out of the orchid's roots, drying out the plant. Therefore, orchids have evolved a special water-conserving mechanism. If you look closely at an orchid's roots, you'll notice the outermost layer has a whitish appearance. That's the velamen, which consists of large dead cells that act as a waterproof barrier, keeping water inside the root. By the way, orchids make lovely houseplants, but you do need to water them occasionally - assuming the air in your house is nowhere near as humid as the air in the Everglades.

These orchid roots are tightly wrapped around the tree to keep the orchid securely in place. The white outer layer is the velamen, which helps keep water from escaping. Orchids' roots play another important role, too. Wind-blown water and nutrients get caught around the roots, where they can be absorbed. Sounds a little bit like room service!

These orchid roots are tightly wrapped around the tree to keep the orchid securely in place. The white outer layer is the velamen, which helps keep water from escaping. Orchids' roots play another important role, too. Wind-blown water and nutrients get caught around the roots, where they can be absorbed. Sounds a little bit like room service!

Oncidium floridanum, also known as Dancing Lady or Florida Orchid, is a Florida native. It is pollinated when a specific genus of bee mistakes its masses of yellow and brown flowers for a swarm of a different type of bee. Being territorial creatures, the bees get all bent out of shape and attack the swarm to scare it away. During their "attack," the bees get pollen stuck to their heads, which is then transferred to another flower during another attack. The specimen in this photo started as one small orchid plant, and over a period of 20 years, has grown to be a massive and beautiful collection of many plants.

Oncidium floridanum, also known as Dancing Lady or Florida Orchid, is a Florida native. It is pollinated when a specific genus of bee mistakes its masses of yellow and brown flowers for a swarm of a different type of bee. Being territorial creatures, the bees get all bent out of shape and attack the swarm to scare it away. During their "attack," the bees get pollen stuck to their heads, which is then transferred to another flower during another attack. The specimen in this photo started as one small orchid plant, and over a period of 20 years, has grown to be a massive and beautiful collection of many plants.

Bromeliads

Bromeliads are often called "air plants." They are usually epiphytic, but they will grow on the ground if they fall out of a tree. (How would they get back up there, anyway?) They are relatives of the pineapple, and many of them do resemble the top of a pineapple since their leaves grow in a lovely rosette pattern around a central core. A notable exception to that is Spanish Moss, whose long, stringy form looks nothing like a pineapple. Every family needs a non-conformist!

Spanish moss (Tillandsia usneoides) is graceful by day, but can be a little creepy at night - especially in cemeteries. It has been used for many purposes, including building insulation, packing material, and stuffing for mattresses and car seats. In the early 1900s, Ford used Spanish moss to stuff the seats in its Model Ts, finding out the hard way that it can harbor chiggers. That left Model T owners scratching their behinds, and supposedly spurred the first automotive recall.

Spanish moss (Tillandsia usneoides) is graceful by day, but can be a little creepy at night - especially in cemeteries. It has been used for many purposes, including building insulation, packing material, and stuffing for mattresses and car seats. In the early 1900s, Ford used Spanish moss to stuff the seats in its Model Ts, finding out the hard way that it can harbor chiggers. That left Model T owners scratching their behinds, and supposedly spurred the first automotive recall.

Air plants' roots are useful for anchoring them to their host tree, but that's about all they're good for. Air plants absorb all the water and minerals they need through special cells on their leaves called trichomes ("hairs"). The fuzziness of the trichomes provides a little protection from intense sun, and also helps prevent water loss. Bromeliads have to open the pores on their leaves during photosynthesis to let carbon dioxide in and oxygen out. Unfortunately, much needed water goes out, too. The hairy trichomes help pull that water right back into the leaf. Brilliant! Mostly, air plants get water and nutrition from what's in the air, but sometimes their host tree helps them out by dripping nutrient rich water on them after a rain.

Bromeliads reproduce by flowers. Some have large, dramatic flowers; others are rather understated. All get the job done by providing nectar to bees, bats, moths and hummingbirds in exchange for their pollen delivery service.

The cardinal air plant (Tillandsia fasciculata) is common in the Everglades. It is several feet across, and has a pretty flower.

The cardinal air plant (Tillandsia fasciculata) is common in the Everglades. It is several feet across, and has a pretty flower.

You see this type of air plant (Tillandsia recurvata) all over the place here in south Florida. (Much to the dismay of Florida Power & Light, they have also been known to grow on power lines and utility poles.) Its flowers are not showy like many other bromeliads'.

You see this type of air plant (Tillandsia recurvata) all over the place here in south Florida. (Much to the dismay of Florida Power & Light, they have also been known to grow on power lines and utility poles.) Its flowers are not showy like many other bromeliads'.

Ferns

We are all familiar with ferns that grow in the soil in shady areas, but some grow as epiphytes. They can really dress up a palm tree!

The ferns growing on this palm tree weren't put there by humans. They showed up all by themselves thanks to spores that blew in on the wind. That's like getting a free wardrobe!

The ferns growing on this palm tree weren't put there by humans. They showed up all by themselves thanks to spores that blew in on the wind. That's like getting a free wardrobe!

Unlike orchids and bromeliads, ferns don't have flowers. They reproduce by sending their spores out on the wind and hoping for the best. As long as the spore lands on a suitable surface, such as rough tree bark or a palm boot, a new fern can grow.

Close-up of spores on a fern leaf.

Close-up of spores on a fern leaf.

Many epiphytes form “traps” with their foliage or roots. The traps on this staghorn fern, for example, capture plant material that eventually rots to provide natural plant food. Yum.

Many epiphytes form “traps” with their foliage or roots. The traps on this staghorn fern, for example, capture plant material that eventually rots to provide natural plant food. Yum.


I'm a bit of a control freak, so I don't think I could be happy as an epiphyte. It would be a little bit like sitting down on the couch without any control over what's on the TV, and having to just hope someone will bring you a snack and a beer. However, I have to admire epiphytes for all the amazing adaptations they have made to successfully live their passive lifestyle in the trees. Everything may be up in the air for epiphytes, but they really know how to make that work.


DID YOU KNOW?

Strangler figs are examples of hemiepiphytes. They start out as an innocent epiphyte, but later turn into a murderous monster. Strangler figs begin life when a seed germinates on a branch of a host tree. (The seed often gets there thanks to a bird who eats the seeds, then leaves a deposit.) Because its roots aren't in contact with the ground, the seedling gets all of its nutrition epiphytically from rainwater, leaf litter and sunlight. Its roots dangle from the host's branches or creep down the host's trunk, striving and reaching for the soil below.

When the fig's roots finally reach the ground, that's when serious trouble starts brewing. At this point, the fig is no longer an epiphyte, and it becomes harmful to the host tree. Its roots get big and woody, encircling the trunk of the host tree. This gives the appearance that the host is being strangled. However, the real problem is that the fast-growing roots steal water and nutrients from the host. At the same time, the fig is growing lots of leafy branches that shade the host so much that it can't get enough sunlight to photosynthesize - which all plants need to survive. Eventually, the host tree dies. By that time, the fig is large and strong enough to stand on its own.

Walking past this strangler fig, it would be easy to overlook the trouble it's causing for the host tree.  Strangler figs are actually quite pretty - as long as you're not its victim.

Walking past this strangler fig, it would be easy to overlook the trouble it's causing for the host tree. Strangler figs are actually quite pretty - as long as you're not its victim.

Here you can see how the strangler fig has completely enveloped a palm tree. The palm is hanging in there - but barely.

Here you can see how the strangler fig has completely enveloped a palm tree. The palm is hanging in there - but barely.


Untitled photo

Epiphytes are fun!


Click here to sign up for the Nature Notes email newsletter. That way, the next time I post a new blog entry, the content will land conveniently in your inbox.


Powered by SmugMug Owner Log In