One of this year's haul of new discoveries was found in Kew Gardens’ Princess of Wales conservatory. Dr Iain Darbyshire, an expert on African botany, stumbled across Isoglossa variegata during a lunchtime wander in the glasshouse. It was first collected nearly 100 years ago but on another specimen from the 1950s there is a note stating “NAME URGENTLY DESIRED”. Fifty years on, the job is now done, the delay reflecting the overwhelming task of charting the world’s plants.

A 'herbarium' specimen of Isoglossa variegata - recently named after being discovered in the Princess of Wales Conservatory. Isoglossa variegata is one of more than 100 new species from East Africa and southern tropical Africa and is part of a major commitment by the Royal Botanic Gardens, Kew, initiated some 50 years ago, to document the flora from this area in two major projects, the Flora of Tropical East Africa and Flora Zambesiaca.

Berlinia korupensis from Cameroon. The Royal Botanic Gardens, Kew, and collaborators in Cameroon have discovered and described more than 100 new plant species in the country since 1995.

Among the most gigantic of the new discoveries are three towering rainforest trees discovered in the Korup National Park in Cameroon. Of these, Berlinia korupensis is the tallest at more than 42m with a buttressed trunk almost 1m wide. Surprisingly, perhaps, the Berlinia is a member of the pea family (Leguminosae). It bears beautiful white flowers from which enormous pods some 30cm in length develop. The pods explode when ripe, propelling the seeds away from the mother tree.

Berlinia korupensis from Cameroon. The seed pods of Berlinia korupensis are 30cm in length..Surveys of the Korup National Park revealed that this tree is extremely rare. “We found just 17 trees in our surveys,” says van der Burgt. “Even though Korup is protected, Berlinia korupensis is critically endangered due to human pressures on the park.”

The bizarre winged fruits of Coffea pterocarpa with their coffee beans inside. Seven wild coffee species, mostly native to the mountains of northern Madagascar, feature on the list. This takes the total number of new coffee species discovered by the Royal Botanic Gardens, Kew and its partners over the past ten years to nearly 30

Winged fruits of Coffea pterocarpa

Beans of Coffea ambongensis the largest seeds of any coffee species: their ‘coffee beans’ are more than twice the size of those of Coffea arabica (Arabica coffee) also pictured, the main species used in the commercial production of coffee.

Two Gymnosiphons - the smallest species on the list. On the right, G. samoritoureanus from Guinea-Conakry in W Africa, discovered 12 months ago, and awaiting publication as a new species. On the left, G. bekensis from Guinea which is not new to science.

Dendrobium chewii, discovered on Mount Kinabalu in Borneo.

Dendrobium jiwhoei, discovered on Mount Kinabalu in Borneo.

Botanist Linda Loffler with Dioscorea strydomiana. Dioscorea strydomiana is a critically endangered species from South Africa with only two populations of about 200 plants known in the wild. It does not look like a typical yam – it is shrub-like in appearance with a huge, slow growing, lumpy wooden tuber above the ground measuring up to 1m in height and diameter. The tuber sprouts multiple shoots each spring. The species is regarded as a cancer cure in the region where it grows and as a result is under threat from over-collection by medicinal plant collectors who cut pieces off the tubers.

Kew’s Director, Professor Stephen Hopper, and his colleague Luke Sweedman (pictured) discovered Eucalyptus sweedmaniana in southwest Australia. It is a dwarf in comparison to most eucalyptus species, forming a low-growing shrub around 1m high. It survives the bush fires that are common in the area by dying back to a woody underground rootstock, known as a lignotuber, from which it can resprout later.

The second new species (Eucalyptus brandiana), although larger than sweedmaniana, isn’t so lucky; it lacks a lignotuber and is killed by fire. Both species are known from just a few hundred plants each and are in need of conservation. However, both have potential as ornamentals in Australia (and perhaps elsewhere), which could provide a welcome backup plan to secure their futures.

Stunning bright flower of the newly discovered Eucalyptus brandiana.

Fourteen species of the blue dye indigo producing genus Indigofera have been described as new to science in 2009. Few natural by-products have played as prominent a role in history and in international trade as indigo. It has been a valued dye from the earliest human civilizations because of its compatibility with all types of natural fibres and its ability to be combined with other natural dyes to create a range of colours not possible to produce with synthetic substitutes. The Royal Botanic Gardens, Kew has had a long-standing interest in the research of this genus and these discoveries arose during ongoing research in southern tropical Africa. Of the 14 new species described, 11 are highly localised and are threatened with extinction. Indigofera has more than 750 species and occurs throughout the tropical regions of the world. It is member of Leguminosae (pea family). This is Indigofera serpentinicola Schrire

Isoetes eludens, a species of an ancient group of spore-plants known as quillworts, and so named because it eluded its discoverers for seven years, was found in a mountain-top rock pool in a remote corner of Namaqualand, South Africa by the Royal Botanic Gardens, Kew’s Director, Professor Stephen Hopper. Botanists are concerned that these exposed temporary rock pools – known by the local Nama people as !gau – are vulnerable to climate change which could mean the 5cm high plant’s days are numbered. Urgent collection of spores and long-term storage in seed banks is an important next step to secure the conservation of this intriguing species. Quillworts date from fossils aged more than 150 million years old in an era before the evolution of flowering plants.

The habitat of Isoetes eludens is a temporary rockpool

Passiflora cristalina is among the 20 new Brazilian species discovered by Kew this year. It is a striking red passionflower with edible egg-shaped fruits and is thought to be pollinated by hummingbirds. Dr Daniela Zappi discovered it during an expedition to the Amazon rainforest in Mato Grosso, Brazil. The plants in this part of the Amazon are poorly known and threatened by deforestation from cattle farming

New Brazilian legume genus Tabaroa catingicola, discovered by Brian Stannard from the Royal Botanic Gardens, Kew and his Brazilian colleagues, on the lower slopes of the Rio de Contas mountain range in southwestern Bahia. The legume family is of great research significance because so many species are used throughout the world as sources of food and medicine. Great potential exists to utilise more species, which is why continued taxonomic research into this family is essential