Plant groups explained

Five major groups of plants were included in the IUCN Sampled Red List Index for Plants. Find out more about them here.

From the results of the IUCN Sampled Red List Index for Plants, it is possible to say for the first time which plants are more threatened, where and why.

The sample of plant species assessed in this project is representative of the world’s plants as a whole, and enough species have been assessed to give much more detail about threats to plants from different habitats and regions. By combining the results for each of the major plant groups, a robust picture of the threats facing plant diversity emerges. Find out more about the key plant groups included in this project below.

Use our interactive chart to find out more about the proportion of all plant species that are threatened and compare the level of threat facing different plant groups.

Examples of monocots - Left: Colour plate from Ernst Haeckel's Kunstformen der Natur | Right: Ophrys apifera (Source: WikiMedia Commons)

Monocotyledons

Monocotyledons, also known as monocots, are a major group of flowering plants. The seedlings usually have a single cotyledon (or seed-leaf) and the leaves are usually parallel-veined. Monocots include orchids, daffodils, lilies, irises, palms, grasses and sedges.

There are around 75,000 different plant species known to science in the monocots group. Globally, the proportion of monocots under threat of extinction is around 22%. Examples of monocots reviewed in this project include:

Mosses are one group of bryophytes (Source: WikiMedia Commons)

Bryophytes

Bryophytes are small, non-vascular plants, such as mosses, liverworts and hornworts. They play a vital role in regulating ecosystems because they provide an important buffer system for other plants, which live alongside and benefit from the water and nutrients that bryophytes collect.

Some bryophyte species are amongst the first to colonise open ground. Bryophytes are also very good indicators of habitat quality as many plant species in this group are sensitive to levels of moisture in the atmosphere, which are lower in disturbed habitats because there is less shade.

Bryophytes do not have seeds or flowers. Instead they reproduce via spores.

There are around 13,000 different plant species known to science in the bryophytes group. Globally, the proportion of bryophytes under threat of extinction is around 15%.

Examples of pteridophytes - Left: Nature print from The Ferns of Great Britain | Right: Athyrium filix-femina unrolling young frond (Source: WikiMedia Commons)

Pteridophytes

Pteridophytes are vascular plants and have leaves (known as fronds), roots and sometimes true stems, and tree ferns have full trunks. Examples include ferns, horsetails and club-mosses. Fronds in the largest species of ferns can reach some six metres in length!

Many ferns from tropical rain forests are epiphytes, which means they only grow on other plant species; their water comes from the damp air or from rainfall running down branches and tree trunks. There are also some purely aquatic ferns such as water fern or water velvet (Salvinia molesta) and mosquito ferns (Azolla species).

Pteridophytes do not have seeds or flowers either, instead they also reproduce via spores.

There are around 13,000 different plant species known to science in the pteridophytes group. Globally, the proportion of pteridophytes under threat of extinction is around 14%. Examples of pteridophytes reviewed in this project include:

Isoetes biafranum
Asplenium mossambicense

Examples of gymnosperms - Left: Encephalartos sclavoi cone | Right: white spruce (Picea glauca) needles (Source: WikiMedia Commons)

Gymnosperms

Gymnosperms are seed-bearing plants, such as cycads, ginkgo, yews and conifers, in which the ovules or seeds are not enclosed in an ovary. The word "gymnosperm" comes from the Greek word gymnospermos, meaning "naked seeds". Gymnosperm seeds develop either on the surface of scale or leaf-like appendages of cones, or at the end of short stalks.

The largest group of living gymnosperms are the conifers (pines, cypresses and relatives) and the smallest is ginkgo, a single living plant species found in China.

There are around 1,000 different plant species known to science in the gymnosperms group. Globally, the proportion of gymnosperms under threat of extinction is around 36%. Examples of gymnosperms reviewed in this project include:

Tree tumbo (Welwitschia mirabilis)

Examples of legumes - Left: varieties of soybean seeds, a popular legume | Right: pea pods (Source: WikiMedia Commons)

Legumes

Legumes are a large and economically important family of flowering plants. Common names used to describe this group include the legume family, pea family, bean family and pulse family.

A common characteristic of plant species in the legume family is the presence of a simple dry fruit that usually dehisces (opens along a seam on two sides). A name often used to describe this type of fruit is a "pod".

Plant species in the legume family grow in many environments and climates and are found throughout the world. Examples of plant species that are important to agricultural trade include: soybean (Glycine max), chickpea (Cicer arietinum), peanut (Arachis hypogaea) and licorice (Glycyrrhiza glabra).

There are around 19,000 different plant species known to science in the legumes group. Globally, the proportion of legumes under threat of extinction is around 12%. Examples of legumes reviewed in this project include: