If you have ever heard about orchids growing on other plants, you might have wondered whether they are feeding on those plants and stealing from their nutrients or not. So, are orchids parasites, or is that a big misconception? Let’s find out!
Many orchids do grow on other plants, but they are not usually parasitic. They do not plug their roots into the plants that they sit on, and they don’t steal nutrients or water from them. Instead, they use them as a platform to lift themselves toward the sunlight, and they aren’t parasitic or harmful. Some rare species of orchids are referred to as parasites, but very few.
What Are Parasites?
Parasites are specifically defined as creatures or plants that survive by stealing some or all of their food/nutrients from other living organisms. For example, a tick is a parasite that latches onto its host and feeds on its blood, thus stealing from and weakening the other organism, albeit only to a small degree.
Most parasites are dependent on their hosts for survival, and cannot cope without the host for long. Again, using the example of the tick, it may be able to survive for some time off the animal, but ultimately, it must return to animals to feed, and without animals, it will starve. It cannot get food in other ways.
As mentioned, some orchids count as parasitic because they feed on and need other organisms, but these are very few. They come from the Corallorhiza genus, and they are not grown in homes or gardens. They only grow in the wild.
These plants rarely grow leaves or roots and they do not photosynthesize. They also don’t produce chlorophyll, and they depend on fungi for their whole existence. So far, no one has successfully cultivated these particular plants.
However, most orchids don’t depend on the host plant for more than a lift off the ground, and if the host plant dies, the orchid can survive on its own because it is almost completely independent of the plant.
As long as the tree remains upright enough to keep the orchid in the conditions it prefers (bright but indirect light, a gentle breeze, and not being too crowded by other plants), the orchid will grow as happily on a dead tree as a live tree, and won’t suffer any ill effects from the loss of its host.
Most parasites die when their host does unless they can move to a new host. They depend on taking advantage of others to survive, and if they can’t do this, they will die. Some parasites may not generate any food at all for themselves, while others just supplement their food by stealing from others.
What Are Orchids, Then?
Orchids are known as epiphytes, which simply means that they grow on something else, rather than in the soil. Indeed, the term means “on top of a plant,” and can refer to various plants that grow on top of other, taller plants.
Not all orchids are epiphytes, but many are, and they tend to grow high up on the branches of trees to get closer to the sunlight. There are also a few other species of plants that include epiphytes, such as bromeliads. Often, epiphytic plants are found in tropical places, as these are the best suited to their evolutionary traits.
Because orchids usually grow in rainforests with dense forest floors and little light available low down, they have adapted to grow further up, where the competition is decreased and there is more light for them.
They are not tall enough to compete with most of the forest floor plants (such as ferns and saplings), so their only option in many cases is to get up off the floor and into trees.
Once up there, they will be above their competitors, giving them more access to light. They will also have a steady supply of nutrients washing over their roots, without having to fight competing plants for these.
You might be wondering how orchids get up into the canopy in the first place, and the answer is that the seeds float up. They are very light, dust-like seeds, and will blow easily on a slight breeze, drifting upward into the canopy. Orchids don’t have to depend on birds or other animals to disperse their seeds because they are so lightweight.
The orchid can then germinate and grow, far above the dense foliage of the forest floor. It will grip onto the tree as its roots develop, and start to suck up moisture and nutrients from the surface of the bark.
What About Orchids That Depend On A “Partner?”
Excluding the Corallohiza genus orchids, you may have heard of other orchids that need a “partner” plant so that they can grow, and some people would argue that these should be called parasitic. They need a kind of mushroom to get food for themselves, particularly when they are seeds.
Some later grow adult leaves and make some of their own food, but some remain dependent or partially dependent on the fungi.
This could be called a parasitic relationship because the plant needs another organism’s input to survive, but the relationship that orchids have with the fungi is usually more of a cooperation (called a symbiotic relationship) in which both organisms benefit. Parasitism does not allow for any benefit to the host plant, so this doesn’t count as parasitism.
More research is needed to really understand how the relationship between orchids and fungi work, and it may vary from species to species, but it is certain that many orchids do depend on fungi for survival, even some adult plants.
Some of the plants are very difficult to cultivate in lab settings because of their dependence on mushrooms. Scientists are learning how to replicate the help that the fungi offer to some degree through nutrient feeds, but it is not yet working well and the orchids tend to be much weaker as a result.
Do Orchids Need A Host?
On the whole, yes, orchids need a host plant when they are in the wild because they need the additional height to pull them away from the forest floor and give them a chance at getting enough sunlight.
However, orchids can be taken away from the host plant if other needs are met and the conditions are right. After all, to grow an orchid in your home, you do not need to plant it on a tree. You just have to create similar conditions, and the plant will grow as happily as if you provided it with a tree trunk.
You might be wondering what those conditions are. It does vary a little depending on the species of orchid, but in general, these plants like humid conditions and reasonably dry roots. They do need water and nutrients, but you will find that epiphytic orchids benefit from these being washed over their roots, rather than stored in the soil.
You can meet these conditions by planting the orchid in orchid bark, which will create a similar environment to those that they would have in a treetop. Their roots will be surrounded by debris, but not packed in at all, meaning that oxygen is still able to flow, and water drains quickly away from them.
Epiphytic orchids that are planted in ordinary soil or compost will not thrive, and will often die because their roots are not designed to deal with the heaviness of soil or the moisture that it traps. They need to be allowed to dry out a bit, rather than sit in water.
This is because the roots are designed to catch and soak up a lot of water very quickly. They are usually fatter than normal plant roots and can hold a lot more moisture as a result, meaning that they don’t need to stay in water for as long because they themselves store water.
Similarly, these orchids may find it easier to absorb liquid nutrients than those in compost, because they are used to taking up trace nutrients that run over the tree bark and collect around their roots. They have not evolved roots that will push down deep into the soil and gather food from there, so there is no point in planting them in deep compost.
In short, orchids don’t need a host provided their other requirements are met, but a host plant is the surest way for them to meet their needs and grow strong. In the wild, orchids are extremely unlikely to survive or even germinate without a host plant to get them started.
So, on the whole, the idea that orchids are parasites is a misconception that has been perpetuated for a long time. Some orchids do depend on the help of fungi in order to survive, and many orchids require a platform of some kind to grow on, but they are not parasitic plants because they don’t tap into their host’s resources and steal them for themselves.