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Least Adder's Tongue Fern

Ophioglossum lusitanicum

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Plant Profile

Ophioglossaceae (Adder's-tongue)
Life Cycle:
Maximum Size:
25 centimetres tall
Grassland, rocky places, sea cliffs, towns.
There are no flowers. Ferns reproduce by means of spores rather than flowers.
The spores ripen in April.
Least Adder's Tongue Fern is an extremely small plant and difficult to spot. Not only that, it is extremely rare and within the British Isles it can only be found on the Scilly Isles. The height of the plant rarely exceeds 2cm tall and it grass-like leaf blades are less than 1cm wide. The plant is a winter annual meaning that it can only be found during the winter period. It is in leaf from October to May and is found on bare ground. Similar in appearance to Adder's Tongue (Ophioglossum vulgatum) and Small Adder's Tongue (Ophioglossum azoricum) but with much narrower leaves.
Other Names:
Portuguese Adder's-tongue.
Frequency (UK):
Rarely seen  

Similar Species

Other Information


Ophioglossum lusitanicum, also known as the Portuguese Adder's-tongue, is a fern species that is native to Europe and North Africa.

It is a small, terrestrial, and endangered species, that grows in rocky crevices, at the base of cliffs, and in damp, shady environments. It is considered to be an endangered species due to habitat loss and degradation caused by human activities like urbanization, agricultural expansion, and the construction of transport infrastructure.

The fronds of O. lusitanicum are small and delicate, typically reaching 15-30 cm high, they are usually single fronds, arising directly from underground rhizomes. The fronds are simple, and triangular in shape, the fertile fronds are smaller than the sterile ones and are located at the base of the plant.

It can be grown in cultivation, but it is difficult to maintain, also it is slow growing and propagates with difficulty, it is best to obtain it from reputable nursery and not collect it from wild. As it is an endangered species, it should be handled with care.

Conservation efforts for this species have been established, including habitat protection, ex situ conservation, and reintroduction programs, but it still requires more protection and management to ensure its survival.


The Least Adder's Tongue Fern, also known as Ophioglossum lusitanicum, is a unique and fascinating species of fern found in various regions of Europe. This plant belongs to the family Ophioglossaceae and is often recognized for its small size and unique reproductive structures. In this blog, we will take a closer look at the characteristics, habitat, and significance of this remarkable fern.


The Least Adder's Tongue Fern is a small plant that typically grows to be around 10-25 cm in height. Its fronds are simple and undivided, and the leaves grow directly from the underground rhizome. The fronds are usually thin and elongated with a characteristic bright green color. One of the most notable features of the plant is the presence of two distinct frond types. The sterile fronds are simple and elongated, while the fertile fronds are much shorter and bear the sporangia, which contain the spores for reproduction.


The Least Adder's Tongue Fern is found in various habitats throughout Europe, including open grasslands, sandy soils, and rocky outcrops. It is often found growing in areas with well-drained soils and plenty of sunlight, but it can also tolerate partial shade. The plant is known to be tolerant of drought conditions, making it well-adapted to survive in dry environments.


The Least Adder's Tongue Fern is a unique and important species in its ecological community. The plant provides habitat and food for various insects, including butterflies and moths. The fern also plays an important role in the nutrient cycle, contributing to the soil fertility and overall health of the ecosystem.

Furthermore, the Least Adder's Tongue Fern is of particular interest to botanists and scientists studying the evolution and genetics of plants. The fern's unique reproductive structures have led to several research studies on the evolution of plant sexuality and the origins of reproductive diversity.

In addition, the fern has been used in traditional medicine for various ailments, including stomach ulcers and respiratory problems. However, it is important to note that self-medication is not recommended, and anyone seeking medical advice should consult a healthcare professional.

The Least Adder's Tongue Fern, with its unique characteristics and ecological significance, is a fascinating species worth exploring. As an important member of its community, the plant plays a vital role in maintaining the health and biodiversity of its ecosystem. Its value extends beyond ecological significance, as the fern has been a source of traditional medicine and an important subject of scientific research. This small plant serves as a reminder of the incredible diversity and importance of the natural world.

Other General Information about the Least Adder's Tongue Fern

While the Least Adder's Tongue Fern is not currently listed as endangered or threatened, it is still important to protect and preserve this species and its habitat. Habitat destruction due to human activity, such as agricultural and urban development, can lead to the decline in populations of this species and other plant and animal species. Additionally, the fern's small size and low visibility can make it difficult to monitor and track its populations. Therefore, it is essential to take necessary measures to protect the natural habitats of the Least Adder's Tongue Fern, including implementing conservation programs, regulating land use practices, and limiting the collection of the plant for scientific research or commercial purposes.

One interesting feature of the Least Adder's Tongue Fern is its unique reproductive biology. The fern has two types of fronds: sterile fronds and fertile fronds. The sterile fronds are the green, elongated leaves that grow directly from the underground rhizome. The fertile fronds, on the other hand, are shorter and bear the sporangia, which are specialized structures that produce spores for reproduction. The sporangia are located on the upper part of the fertile fronds and are arranged in a spike-like structure called a "sporophore." The sporangia of the fern are unique because they are split into three valves, with each valve containing a row of spores.

The Least Adder's Tongue Fern is also notable for its use in traditional medicine. The plant has been used for centuries as a remedy for various ailments, including digestive problems, respiratory issues, and skin conditions. The fern contains several chemical compounds, including flavonoids and saponins, that have been shown to have therapeutic properties. However, it is important to note that the effectiveness and safety of using the plant for medicinal purposes have not been extensively studied, and self-medication is not recommended.

The Least Adder's Tongue Fern has been the subject of several conservation initiatives in Europe. For example, in Portugal, the fern is protected by law, and it is illegal to collect or damage the plant. In Spain, the fern is listed as a "species of special interest," and it is protected by regional conservation laws. These conservation efforts are essential for maintaining the health and diversity of natural ecosystems, and they ensure that future generations can continue to enjoy the unique beauty and ecological significance of this fascinating fern species.

Another interesting aspect of the Least Adder's Tongue Fern is its ability to reproduce asexually through the production of bulbils. Bulbils are small, vegetative structures that can develop at the base of the fronds. These bulbils can break off and grow into new plants, creating clones of the parent plant. This mode of reproduction allows the fern to rapidly colonize new areas and is an important adaptation for survival in unpredictable or harsh environments.

The Least Adder's Tongue Fern is also an important plant species for scientific research due to its unique reproductive structures. The fern has been used as a model organism for studying the evolution of plant sexuality and the development of reproductive diversity. For example, researchers have used the fern to study the genetic and developmental mechanisms underlying the formation of sporangia and spores, and to investigate the role of sex chromosomes in plant reproduction.

Finally, the Least Adder's Tongue Fern is not just an important species in its natural habitat but also in cultivation. The fern is occasionally grown as an ornamental plant due to its attractive fronds and unique reproductive structures. It can be grown in a variety of soil types, including sandy and well-drained soils, and it can tolerate drought conditions. As an ornamental plant, the fern can be grown in pots, rock gardens, or as a ground cover in dry, sunny areas.

In summary, the Least Adder's Tongue Fern is a unique and fascinating species with several notable features, including its reproductive structures, medicinal properties, and importance for scientific research. As an important member of its ecological community, it serves as a reminder of the incredible diversity and complexity of the natural world and the need to protect and preserve it for future generations.

Distribution Map

Reproduced by kind permission of the BSBI.

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