Did you know there are more than 20,000 types of orchids in the world? That’s more than four times the number of mammal species! While most are found in tropical rainforests and grasslands in far off places, a fair amount are also native to the United States. A favorite in homes worldwide, the “Orchidaceae” family features blooms that are vibrant, tropical and fragrant.
The Orchidaceae family is one of the most species-rich families of flowering plants, with over 20,000 species. It is commonly divided into 5 subfamilies: Cypripediodeae, Vanilloideae, Orchidoideae, Epidendroideae, and Apostasiodeae. Subfamilies are further divided into smaller tribes, which are then divided into subtribes and grouped into genera.
Orchid flowers are all bilaterally symmetrical with three petals and three sepals. Their seeds develop in capsules and are extremely tiny, sometimes mistaken for dust or spores. Because the seeds are so small, they don’t contain enough nutrition to grow a new plant themselves, so they develop a symbiotic relationship with fungus, which provides the nutrients for them to grow.
The Cypripedioideae subfamily is known for its lady slipper orchids, which are named after their slipper-shaped pouches that trap insects and help the flowers get pollinated. There are 5 genera in this subfamily: Cypripedium, Mexipedium, Paphiopedilum, Phragmipedium, and Selenipedium. Cypripedioideae orchids have two lateral, fertile anthers, which is unusual in most other orchids.
Orchids in the Cypripedieae tribe are believed to be some of the most primitive orchids. This tribe consists of 4 genera with over 100 species that are distributed in boreal, temperate, and tropical regions throughout Europe, Asia, and America. Some have argued that this subfamily should be a distinct family separate from Orchidaceae.
The Vanilloideae subfamily is an ancient group that includes the only orchids from an ancestor of agricultural value — vanilla. This subfamily consists of the tribes Pogonieae and Vanilleae, and has about 15 genera and 180 subspecies. Orchids from this subfamily exist throughout Asia, Australia, and the Americas in pantropical areas.
The Pogonieae tribe consists of 5 genera that are distributed from North to South America and East Asia. Orchids in this tribe are known for their unique lip margin, which appears fringed or jagged. Most species are pink or purple.
The Vanilleae tribe is divided into 3 subtribes consisting of 10 genera. Of these genera, Vanilla is the only genus that is pantropical in distribution, and all genera except Vanilla have very few species. Vanilleae orchids are characterized by their long, thick, succulent vines.
The Orchidoideae subfamily is a large group that consists of 7 tribes and 3,630 species. These orchids have showy flowers that are arranged in an erect or arching terminal inflorescence. They are distinguished by their single, fertile anther. Members of the Orchidoideae subfamily can be found worldwide.
The Orchideae tribe is the largest tribe within the Orchidoideae subfamily, and contains a variety of flower forms. Flowers in this tribe dominate the orchid flora in the temperate Northern Hemisphere, though they can also be found in East Asia. These orchids usually have a three-lobed lip without a basal spur, prominent caudicles, and erect anthers.
The Cranichideae tribe consists of about 90 genera and 1699 species. They can be found on all continents except Antarctica, though are most diverse in tropical and subtropical regions. They often have small, tubular flowers that do not open widely, and soft herbaceous leaves.
The Epidendroideae subfamily is the most widespread subfamily. It represents more than eighty percent of orchid species, and includes over 10,000 types of orchids. Although members of the Epidendroideae subfamily are present in temperate regions, they are most prevalent in the tropics of the Eastern and Western hemispheres. There orchids typically have single anthers with sub-erect structures.
The Arethuseae tribe consists of 26 genera that can be found in Asia, New Guinea, the southwest Pacific Islands, eastern North America, and the northern Caribbean. This tribe was originally categorized by John Lindey in 1840, and contained over 90 genera, but was recategorized by Robert Dressler in the late twentieth century.
The Neottieae tribe consists of 3 genera. It is distributed throughout the world including Europe, tropical Africa, Sri Lanka, Southeast Asia, China, Japan, New Guinea, and Australia. In the Western Hemisphere, it is found in the western United States, Central America, and South America. They have fleshy, but slender roots, and thrive in temperate habitats.
The Triphoreae tribe has about 4 genera and 28-30 species. Orchids in this tribe are commonly found in North America, Central America, and South America, though one species can be found in tropical West Africa. They have a slender stem, fleshy roots, which often have nodular tuberoids, and small flowers.
The Calypsoeae tribe consists of about 12 genera and 70 species. It is widely distributed in Europe, northern Asia, North America, Central America, the Caribbean, and South America. The species in this tribe are typically terrestrial, and the most popular genera are Governia, Oreorchis, and Corallorhiza.
This tribe is fairly large and consists of four genera — Dendrochilum, Pholidota, Chelonistele, and Coelogyne — and over 300 species. They are native to the tropical and subtropical regions of the Old World. Coelogyne is the most popular genus. Its orchids are characterized by a three-lobed lip that is concave at the base, and a hooded or winged column.
The Cymbidieae tribe consists of about 1800 species and over 100 genera. The tribe exists in tropical regions throughout the world, and species are either terrestrial or epiphytic. Orchids in this tribe are unique in that they have two pollinia (masses of pollen grains) and a sympodial growth habit.
Collabieae is a somewhat neglected tribe with little understanding of its phylogenetic relationships. It’s a medium-sized tribe with about 500 species that are primarily distributed in the Old World tropics. This tribe displays a variety of vegetative and floral variations, including lateral and terminal inflorescences.
The Malaxideae tribe consists of about 1000 species, and is distributed in temperate and tropical areas throughout the world. The flowers are typically small and they have terminal inflorescence. Malaxideae are unique in that they contain high numbers of both obligate terrestrial and epiphytic orchids.
The Epidendraea tribe consists of six subtribes: Bletiinae, Chysinae, Coeliinae, Laeliinae, Pleurothallidinae, and Ponerinae. It includes 86 genera, which are found in the Caribbean, and North America, South America, and Central America. The Epidendraea tribe primarily consists of tropical epiphytic orchids.
The Maxillarieae tribe is large and complex, consisting of about 70 genera and over 1000 species. Orchids from this tribe are primarily found in Central and South America. Overall, this group has diverse vegetative habits, floral morphology, and pollination mechanisms.
Vandeae is a large tribe that consists of nearly 2000 species. Orchids within this tribe are primarily classified based on floral morphology. The tribe consists of epiphytes, which are plants that grow harmlessly on other plants. It can be found in pantropical areas including Africa, Asia, and America.
The Tropidieae tribe is a pantropic tribe consisting of about 2 genera and 43 species. Orchids in this tribe have loose pollen and an erect anther. Their flowers are commonly arranged in clusters around the main stem, and are often pale green, white, or yellow.
To give you a better feel for how orchid subfamilies, tribes, and genera are interconnected, we created a compendium of popular American orchids. It plots over 100 “local” genera of orchids so you can see just how impressive and expansive this family is. You may be surprised that some of these vibrant, exotic-looking orchids exist in your own backyard! Want to learn more about flowers and plants? Check out our other compendiums featuring types of roses and types of desert plants.
Inspired by orchids?
Browse our orchid bouquets, which include the Dendrobium and Cymbidium genea you see in this guide!
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Vanilla Orchids: Natural History and Cultivation by Ken Cameron
Orchid Biology VIII: Reviews and Perspectives ed. Tiiu Kull, J. Arditti
An Atlas of Orchid Pollination: European Orchids by Nelis A. Van Der Cingel
The New Encyclopedia of Orchids: 1500 Species in Cultivation by By I. F. La Croix
Orchids of Asia by By Eng-Soon Teoh
Monocots: Systematics and Evolution: Systematics and Evolution edited by Karen L Wilson, David A Morrison
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