Equisetum

Horsetails are green plants.

They look like a horse's tail. This is why they have that name.

These plants are very old. They lived a long time ago. Some were even big trees.

The stems have tiny bits of grit. This grit helps clean metal pots.

They make seeds called spores. These spores help new plants grow.

Horsetails are very old plants. They are often called "living fossils."

These plants lived over 100 million years ago. Some ancient relatives were even tall trees. Modern horsetails first appeared during the Jurassic period.

Most horsetails have green stems. The stems are hollow and have ridges. They also have joints.

The stems contain tiny bits of grit called silicates. This grit makes the plant feel rough. People used to use them to clean metal pots. In Japan, some people use them to polish wood.

Horsetails do not make seeds. Instead, they use spores to grow. Spores are found in cone-like parts called strobili.

These spores have four tiny parts called elaters. These parts act like springs. When the spores get wet, the elaters help them move. This helps the spores spread to new places. Most horsetails grow between 20 cm and 1.5 m tall.

Horsetails are a very special group of plants. They belong to a family called Equisetaceae. These plants are often called "living fossils." This is because they have been around for a very long time. For over 100 million years, their relatives were much more diverse. Some of those ancient relatives were even giant trees. Modern horsetails first appeared during the Jurassic period.

These plants have a very unique way they work. Most horsetails have green stems that make food from sunlight. The stems are hollow and have many ridges. They also have joints called nodes. The leaves are very small and often do not make food. Instead, the leaves grow in circles around the nodes. Sometimes, branches grow from buds between these leaf groups.

Horsetails do not use seeds to make new plants. Instead, they use tiny bits called spores. These spores are found in cone-like structures called strobili. These strobili grow at the tips of some stems. The spores have four tiny parts called elaters. These elaters act like moisture-sensitive springs. When they get wet, they help the spores hop and crawl to new places.

Scientists have studied these plants for a long time. The name "horsetail" comes from how the branched plants look like a horse's tail. The scientific name Equisetum comes from Latin words for "horse" and "bristle." Long ago, a man named John Napier was inspired by these plants. He looked at how the spaces between the nodes changed. This pattern helped him invent logarithms.

Many people find horsetails useful in daily life. The stems are coated with tiny bits of grit called silicates. This makes the plants feel very rough. In the past, people used them to clean metal pots. In Japan, a type called rough horsetail is used for woodcraft. It is boiled and dried to polish wood until it is smooth.

Equisetum, commonly known as horsetail, is a unique genus of vascular plants. Unlike most common plants, they reproduce using spores instead of seeds. They belong to the family Equisetaceae. Scientists often call them "living fossils." This is because they are the only living members of the subclass Equisetidae. For over 100 million years, this group was much more diverse. During the late Paleozoic, their relatives dominated the understorey of forests. Some ancient relatives, like the genus Calamites, were large trees.

The physical structure of a horsetail is quite distinct. The stems are usually green and perform photosynthesis. They are hollow, jointed, and feature several ridges. Most stems have about 6 to 40 ridges. The leaves are greatly reduced and often do not perform photosynthesis. These leaves are arranged in whorls, which are circles, fused into nodal sheaths. The leaves are considered microphylls. This means they contain a single, non-branching vascular trace.

Reproduction in Equisetum happens through a specialized process involving spores. These spores are held in cone-like structures called strobili. These strobili grow at the tips of certain stems. In some species, like field horsetail, the spore-bearing shoots are non-photosynthetic. The spores themselves have four unique parts called elaters. These elaters act like moisture-sensitive springs. When the sporangia split open, the elaters help the spores move through crawling and hopping motions. This assists in spore dispersal.

There are several different lineages within the genus. Scientists currently recognize 18 species, though some researchers suggest there are 25. The living members are divided into three main subgenera. One is the subgenus Equisetum, which includes the common field horsetail. Another is the subgenus Hippochaete, which includes the rough horsetail. A third is the subgenus Paramochaete, which contains the Andean horsetail. Hybrids are common between species within the same subgenus.

The history of these plants stretches back to the Jurassic period. The oldest remains of the modern genus appear in the Early Jurassic. Examples include Equisetum dimorphum from Patagonia and Equisetum laterale from Australia. In Argentina, fossils called Equisetum thermale show the same features as modern plants. The pattern of the nodes on these plants is historically significant. The way the spacing between nodes changes toward the tip inspired John Napier. He used this pattern to invent logarithms.

Horsetails possess unique chemical properties in their cell walls. They contain a polysaccharide called mixed-linkage glucan, or MLG. This substance was once thought to exist only in the Poales group. Equisetum also contains a novel enzyme called MXE. This enzyme is not found in any other plants. Research suggests MXE might help control cell expansion. The presence of these substances shows how Equisetum evolved separately from other plant groups.

Humans have used the physical properties of horsetails for many tasks. The stems are coated with abrasive silicates. This makes them very rough to the touch. Because of this, they were used as "scouring-rush" to clean metal items. People used them to scrub cooking pots or tin mugs. In Japan, the species Equisetum hyemale is used for woodcraft. It is boiled and dried to provide a final polish on wood. This creates a very smooth finish.

Today, horsetails are found almost everywhere in the world. They are near-cosmopolitan, meaning they are found in most places. They are naturally absent only from Antarctica, Australia, New Zealand, and Pacific islands. They are very common in northern Europe and northern North America. Most species are perennial, meaning they live for many years. Some species are evergreen, while others die back in the winter. They typically grow between 20 cm and 1.5 m tall. However, subtropical giant species can grow much higher.