Orchids are often thought of as beautiful, delicate and vibrant -- but a newly identified plant might just change your mind.

The "Gastrodia agnicellus" -- labelled the "ugliest orchid in the world" -- is one of this year's newly described plants and fungi, researchers from the Royal Botanic Gardens, Kew (RBG Kew) have announced.

The orchid, located in Madagascar, has no leaves, grows from a woolly tuberous stem, and spends most of its life underground, emerging only to flower or produce fruit.

Beauty is in the eye of the beholder, Johan Hermans, a researcher on orchids behind the find, told CNN on Thursday.

Still, he said: "It's not very attractive, I must say -- it's fleshy looking, red inside and brown on the outside."

"We first saw it in seed pod. A couple of years later we went back and searched that same area, trying to find a brown flower on brown leaf litter, and eventually we did find it," Hermans, an honorary research associate with RBG Kew, explained.

"It was sort of hidden at the base of the tree, and you had to remove the leaves to find where the plant was," he added.

Researchers thought that the strange looking plant might smell like rotten flesh, as is common in some orchids pollinated by flies, but instead, the orchid surprised them with a "pleasant, citrusy, rose scent," Hermans said.

"This orchid's got an amazing life cycle -- it's got an on-the-ground woolly tuber, no leaves, and the flower slightly pops up underneath the leaf litter.

"It opens only a little bit, it gets fertilized and the seed sort of fruits and actually lifts itself on quite a long stork about 20 centimetres (7.9 inches) tall, then it opens and distributes the seed."

Some 156 plants and fungi around the world were found and officially named by RBG Kew and partners in 2020, including a scaly leafed shrub from southern Namibia, a relative of the blueberry found in New Guinea, and a new variety of hibiscus in Australia.

But several of these plants are already under threat of extinction due to threats to their habitats, RBG Kew warned on Thursday.

Some 40 per cent of the world's species of plants are threatened with extinction, RBG Kew said earlier this year, with the annihilation driven by soaring deforestation rates, global emissions and climate change, threats posed by new pathogens and non-native species and illegal trade in plants.

A sixth mass extinction -- caused by humans -- is underway, and experts say it's happening faster than previously expected.

One million of the planet's eight million species are threatened with extinction by humans, a UN committee warned last year, adding that "transformative change" was needed to save the planet.