Orchids are popular flowering plants with colorful and fragrant blooms. There are around 28,000 species of orchids distributed all around the world. In nature, many orchids grow on trees and bushes, causing many people to wonder if an orchid is a parasite.
No, orchids aren’t parasites. In their natural habitat, many species of orchids grow by clinging to trees and bushes. But they don’t take anything from the host plant and don’t harm it in any way. Orchids that grow on trees are called epiphytes or air plants. They absorb nutrients and moisture from the air surrounding them, not relying on trees for food.
Keep reading to learn more interesting facts about orchids. In this article, you’ll also find information about the best-known parasitic plants.
What are Orchids?
Orchids are a diverse and widespread group of flowering plants that belong to the family Orchidaceae. The Orchidaceae family has around 28,000 accepted species currently and is one of the two largest families of flowering plants.
Most species of orchids grow in rainforests, soaking up humidity and enjoying the shade provided by these environments. Not all types of orchids love hot environments, though.
Species growing at high altitudes in the mountains, where temperatures drop very low at night, need cooler climates to thrive.
Many forest-dwelling orchids grow as epiphytes, which means they grow on trees using aerial roots to cling to tree bark and store water in fleshy leaves or thick stems called pseudobulbs. Orchid species that grow in the ground are known as terrestrial.
Lithophyte orchids grow on rocks using their roots to attach themselves to cracks in rocks. Saprophyte orchids are photosynthetic and need sunlight to survive. But because they can’t rely solely on photosynthesis to provide all necessary nutrients, they found a way to break down organic matter.
Are Orchids Parasitic or Symbiotic?
Around three-quarters of all orchid species are epiphytes, meaning they live and grow on other plants. Orchids growing on trees form special symbiotic relationships with their hosts.
There are several types of symbiotic relationships between organisms, including:
- Mutualism – A relationship between two different species where both species benefit
- Parasitism – A relationship where one organism, the parasite, receives benefits at the expense of the host organism
- Commensalism – Is a relationship between two living organisms where one organism benefits, but the other organism isn’t harmed or helped
- Amensalism – This is a type of relationship in which one organism is completely destroyed while the other organism is unaffected
Some species of orchids form a complex symbiotic relationship with mycorrhizae. Luckily for the orchid and the fungi, their symbiotic association benefits both parties.
In the early developmental stages, juvenile orchids rely entirely on mycorrhizal fungi to supply nutrients.
Most species of orchids grow in habitats with limited sunlight. Without sunlight, an orchid can’t produce chlorophyll.
Because orchids can’t produce chlorophyll on their own, they rely on mycorrhizal fungi to help. The fungi can digest plant matter found in the surrounding area, converting it into simpler molecules that orchids can absorb.
Young orchids depend on the fungi so much that they must wait for the fungi to invade their seed before the orchid can even start germinating. During this initial phase, the fungi get nutrients from the host plant, while the orchid seed obtains an energy boost from the fungi.
All orchids depend on mycorrhizal fungi at the beginning of their life cycle. But as they mature, some species begin to produce their own source of food. Some species of orchids become photosynthetic, meaning they can make their own organic carbon.
At this point, you’re probably wondering what the fungi get in return. The mycorrhizal fungi get moisture and food from this symbiosis. The fungus digests vascular plant matter found among the orchid’s roots and keeps it moist because of the orchid’s water-rich environment.
Most epiphytic orchids form commensal, symbiotic relationships with trees. The orchid benefits from these types of relationships, and the tree isn’t in any way affected.
What Are 5 Examples of Parasitic Plants?
A plant, insect, or animal is considered a parasite when it lives on or inside another species, called the host, and obtains its nutrients at the host’s expense.
Parasitic plants are classified as holoparasites and hemiparasites. Holoparasites depend entirely on the host, while hemiparasites get only a part of their nutrients from the host.
The best-known examples of parasitic plants are:
1. Corpse Flower
The corpse flower is native to rainforests on the Indonesian island of Sumatra. It has the largest unbranched inflorescence in the world.
This plant lacks leaves and is an obligate parasite because it can’t photosynthesize on its own.
Dodder is a common parasitic plant that uses root-like organs called haustoria to penetrate the stems of their hosts to get water and nutrients. These plants have little or no chlorophyll with which to make their own nutrients, so young seedlings must find a host fast.
3. Thurber’s Stemsucker
Native to the deserts of North America, the Thurber’s stem-sucker is only 0.25 inches long. This small plant lacks leaves, roots, and chlorophyll and lives entirely within the stem tissues of its host.
4. Australian Christmas Tree
The Australian Christmas tree is a tall, flowering tree native to dry regions in southwest Australia. This plant has leaves and can photosynthesize, but it acts as a parasite and steels water from the neighboring plants as necessary.
5. Dwarf Mistletoe
Dwarf mistletoe is found worldwide and primarily targets conifer trees. Like dodder, dwarf mistletoe uses haustoria to penetrate the host’s tissues and create little to no photosynthesis on its own.
Although most orchids cling to trees and bushes, they aren’t parasites. Unlike true parasitic plants, orchids don’t take anything from their hosts and don’t rely on trees and bushes to get the necessary nutrients.
Orchids form symbiotic relationships with their hosts. In most cases, these vibrant plants establish mutualistic and commensalism relationships in which the host organism isn’t harmed or injured in any way.