We've all heard about the most endangered animals. Creatures like the critically endangered black rhinoceros are famous, and in some cases have been reduced to just a handful of individuals.
But what are the most endangered plants? They might not be as exciting or loveable as animals, but they are just as important to the ecosystem – and humanity relies on that ecosystem.
Here are nine of the most threatened plants today. They are almost all classed as critically endangered by the International Union for Conservation of Nature (IUCN). These plants occupy some of the most inaccessible, remote parts of our planet. They are threatened by habitat destruction, illegal collection, poaching, and competition with invading species.
Attenborough's pitcher plant is known only from the relatively inaccessible summit of Mount Victoria in Palawan in the Philippines. There are thought to be only a few hundred of them.
Pitcher plants are carnivorous plants that trap animals in liquid-filled bowls called pitchers. Attenborough's pitcher plant is one of the biggest, with pitchers up to 30cm in height that can trap insects and rats.
It was only discovered in 2007 when a team of botanists, tipped off by two Christian missionaries, scaled Mount Victoria. It is named after British natural history broadcaster David Attenborough.
The suicide palm is a gigantic palm found only in remote parts of north-west Madagascar. It lives for about 50 years, then flowers only once, and dies soon after.
Suicide palms were discovered in 2005, by a cashew plantation manager during a family outing, and formally described in 2008. With trunks reaching 18m in height, and huge fan-leaves up to 5m across, the palms can be seen on Google Earth. There are only about 90 in the wild.
This unusual orchid spends its entire life underground. It even flowers underground, in late May and early June, producing more than a hundred cream to reddish flowers, and a strong fragrance.
It only lives in the Broom bush shrubland in western Australia. It lacks chlorophyll so cannot draw energy from sunlight like most plants. Instead it takes nutrients from the roots of broom bush, by parasitizing the fungi associated with it.
There are thought to be fewer than 50 plants. The species has not been assessed by the IUCN, but Western Australia classes it as critically endangered.
Found only in the mountains of Queretaro in Mexico, the golf ball is a small white-ish cactus that looks, you've guessed it, like a golf ball. Its beautiful pink flowers have made it popular among horticulturists, so many wild cacti are illegally collected. As a result, the population has dropped more than 95% over the last 20 years.
The hairy-looking Venda cycad is only known from Limpopo province in South Africa. It was first described as a new species in 1996.
Like the golf ball it is threatened by people who illegally collect them for ornamental purposes, and its population has been declining. Unconfirmed reports suggest that the Venda cycad is now extinct in the wild.
The jellyfish tree was thought to be extinct, until it was rediscovered in the 1970s. It may have got its name from its fruit, which looks like a jellyfish when broken open.
The only living member of the family Medusagynaceae, it lives on the island of Mahe in the Seychelles. There are only about 86 mature jellyfish trees left in the wild, and some of them do not reproduce any more.
The poke-me-boy tree is an extremely spiny shrub found only on the islands of Anegada and Fallen Jerusalem in the British Virgin Islands. These islands are low-lying so the trees could be swamped by sea level rise.
The state of the population is unknown, but the species is known to occur in an area of less than 10 sq km. To boost their chances of survival, mature poke-me-boy trees are being cultivated in the nearby JR O'Neal Botanic Garden on Tortola, and at the Royal Botanic Gardens in Kew, UK.
This tiny fern looks like a miniature parsley plant. It is found only on Ascension, a volcanic island in the south Atlantic Ocean.
For over 50 years it was believed to be extinct, until 2009 when a team of botanists chanced upon four ferns. They were growing precariously on an unstable cliff face of Ascension's Green Mountain, in harsh and dry conditions.
To save the few survivors, the researchers tended them for weeks, going down the ridge with a safety rope to water them and remove weeds. As soon as the plants began to produce spores, the team cut small parts out of the ferns' spore-forming parts, and sent them to the Royal Botanic gardens in Kew, UK for propagation.
However, the fern is still extremely rare, with about 40 mature individuals in the wild.
The coral tree, with its bright red flowers and spiny trunk, occurs only in the remote forests of south-east Tanzania.
It was declared extinct in 1998, but rediscovered in 2001 in a small patch of forest. However, the forest patch was cleared to grow biofuels, and the species was feared to have gone extinct again, until it was re-rediscovered in 2011.
There are now fewer than 50 mature individuals in the wild, in a single unprotected location.