Aloina rigida
Common Name: Rigid Aloe-Moss, Conservation Status - Least Concern (Campisi et al. 2019)
There has been a lot of debate regarding whether A. ridiga and A. obliquifolia should be considered separate species, as they currently are, or combined into one species with two subspecies (Campisi et al., 2019).
Appearance and Identification
Much like the other Aloina species found in the UK A. rigida is dioecious, and grows exclusively in small, scattered patches of vertical tufts, often alongside other acrocarpous species (Blockeel, 2014a; Campisi et al., 2019; Hill et al., 2017). Along with A. brevirostris, it is the smallest Aloina species in the UK, standing at just 1-2mm tall. Again, similar to the other Aloina species, A. rigida looks remarkably like a very small succulent plant. Its short leaves are stiff, incurved, and arranged in a rosette pattern, they also have rounded tips and an untoothed leaf margin (Pilkington, 2010). They are usually dark green in colour, but leaves may fade towards brown near the tips in some specimens.
In contrast to the small size of A. rigida's leaves and shoots, the seta can grow very tall, usually many times the height of the main leafy body. It is also quite common to see seta and capsules on specimens of A. rigida, as sporophytic plants are very common in this species, especially between Autumn and Spring (Blockeel, 2014a; Hill et al., 2017; Pilkington, 2010). Capsules are also large relative to the rest of the plant, and have pointed, hairless calpytra.
Similar Species:
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Aloina aloides - the main difference is size, with A. aloides being slightly larger than A. rigida (Pilkington, 2010), although this may be difficult to determine if specimens are not side by side. Other differences include A. rigida having shorter, more rounded leaves as well as border of hyaline cells near the base of the leaf which can sometimes be seen under a microscope (BIBS, n.d.; Pilkington, 2010). A. aloides is also much more common and widespread in the UK than A. rigida, which does not occur in coastal habitats, is rare in Wales, and can no longer be found in Ireland (Blockeel, 2014a; Blockeel, 2014b; Hodegetts & Lockhart, 2025; Pilkington, 2010).
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Aloina ambigua - larger with longer, narrower, and more pointed leaves, and is also at least twice as common as A. rigida in the UK. It also has a slightly different distribution, occurring in coastal habitats and Ireland, but not in Scotland (Hill et al., 2017; Hodgetts & Lockhart 2025; Pilkington, 2010).
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Aloina brevirostris - very difficult to tell apart, especially when out in the field. Although, A. brevirostris is less common than A. rigida, and can only be found in England and Wales at altitudes below 225m above sea level (Hill et al., 2017; Pilkington, 2010).
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Pogonatum nanum - Particularly small P. nanum individuals may somewhat resemble A. rigida, although a quick check for toothed leaf margins and hairy calyptra will clear up any confusion. P. nanum also does not grow in the dry, calcium-rich soil which A. rigida prefers, it is instead found in moist, acidic soils (Hill et. al., 2017).
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Polytrichum juniperinum - also has its leaves arranged in a rosette shape, however is not only significantly larger than A. rigida, but is also exclusively found in acidic environments, while A. rigida needs calcium rich, basic soils to grow (Hill et al., 2017)
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Polytrichum piliferum - also has its leaves arranged in a rosette shape, however is not only significantly larger than A. rigida, but is also exclusively found in acidic environments, while A. rigida needs calcium rich, basic soils to grow (Hill et al., 2017).
A. rigida is incredibly rare in Kent, with only two sightings, both in the same area, recorded by Jan during her time as the county recorder for Kent and likely because of this there were no dried specimens of this species in her collection. Therefore, if you do manage to find a population of A. rigida in Kent I would advise against taking samples, unless it is a particularly large population.
(Barbottin, 2016)
(Barbottin, 2016)
Distribution
A. rigida is a very widely distributed moss, it can be found in most parts of the Northern hemisphere (Asia, Europe, and North America), which do not fall within the Arctic circle. This includes a continuous distribution across Europe and Asia, which starts in the Azores and Canary Islands and travels up through the British Isles and mainland Europe, being absent only from Norway and Sweden (Blockeel, 2014a; Campisi, et al., 2019). It then continues through central Asia and Russia, all the way to the Yakutia region in the east, as well as down towards the Arabian Peninsula (Blockeel, 2014a; Hradílek et al., 2011; Ignatov et al., 2006). This species can also be found in Australia, Central Africa, and several South American countries (Argentina, Bolivia, Ecuador and Peru) (Blockeel, 2014a; Jimenéz et al., 2020). Throughout its range the primary habitat for this species is temperate and Mediterranean shrubland, but it is also found in rural gardens and urban areas (Campisi et al., 2019). Although there are no large scale threats to this species, populations are usually very small, and local declines have caused this species to be regionally threatened in certain countries (Campisi et al., 2019). A. rigida is considered Near Threatened in Madeira, Germany, Luxembourg, Netherlands, Switzerland and Hungary, Vulnerable in Estonia, Endangered in Portugal and Austria, and Regionally Extinct in Ireland and Northern Ireland (Hodgetts & Lockhart, 2020).
A. rigida is no longer found in Ireland, and has never been recorded in the Channel Islands, but does have a scattered distribution across the rest of the UK. It is slightly more common in the east of the country, with no sightings in the south west of England, and very few in Wales (Blockeel, 2014a; Hill et al., 2017; Hodgetts & Lockhart, 2025). In the past this species was common on mud-capped walls, but more recently the availability of this habitat has been declining, especially in the south. Other good places to look for this species in the UK are areas of bare found on limestone or chalk based soils (Blockeel, 2014a). According to Jan there have only ever been three observations of A. rigida in Kent, one in Burnham Chalk pit in the 1870's, and two in Charing Chalk Pit in 2013 and 2014.
UK Altitudinal Range: 10-500m (Blockeel, 2014).
Habitat and Ecology
A. rigida is a perennial species (Hill et al., 2017), so can be seen at any time of the year.
A. rigida grows best in dry, well-lit environments, but is able to tolerate moist substrates. It also requires very basic and calcium rich substrates, although does not need soils to have free calcium carbonate, its presence usually indicates soils which are low in nitrogen and therefore, quite infertile (Hill et al., 2017). As A. rigida prefers areas with low levels of vegetation it is is common on bare soil or very rock areas, although cannot grow directly on rocks and does need at least a thin layer of soil or hummus. Chalk and limestone cliffs, old quarries, rocky ledges, and open calcareous slopes are therefore all good habitat for this species There have also been a few reports of this species growing near slag heaps, but this is considered an 'unusual habitat', and has so far only been observed in Cumbria (Blockeel, 2014a; Campisi, et al., 2019). The total list substrates which A. rigida can grow on in the UK is; soil on rock, soil, gravel and sand, and the complete list of habitats in which it can be found is; inland cliffs, rocks and pavements, inland habitat with low levels of vegetation, low density buildings, and extractive industry sites (Hill et al., 2017).
Associated Species: Drought tolerant acrocarpous mosses, occasionally including A. ambigua (Blockeel, 2014a; Campisi et al., 2019).
Regional Threat Level
British Red List: The most recent review of regional red list statuses for British bryophytes listed A. rigida as Least Concern (Callaghan, 2022), although in a slightly older review of bryophytes in Europe, its British red list status was listed as Endangered (Hodgetts & Lockhart, 2020). The species has undergone historical declines in Britain, but the current population is stable, despite A. rigida being somewhat scarce here (Callghan, 2022). It can currently be found in 39 hectads in Britain, and is therefore, considered Nationally Scarce (Callaghan, 2022; Pescott, 2016).
Irish Red List: A. rigida is regionally extinct in both Ireland and Northern Ireland (Hodgetts & Lockhart, 2025).
References
Barbottin, A. (2016a). Individus de A. rigida [Graphic]. Own work. https://commons.wikimedia.org/wiki/File:Aloina_rigida_-_Alban_Barbottin02.jpg
Barbottin, A. (2016b). Individus de A. rigida [Graphic]. Own work. https://commons.wikimedia.org/wiki/File:Aloina_rigida_-_Alban_Barbottin01.jpg
Blockeel, T. J. (2014a). Aloina rigida. In T. J. Blockeel, S. D. S. Bosanquet, M. O. Hill, & C. D. Preston (Eds), Atlas of British and Irish Bryophytes (Vol. 2). Pisces Publications.
Blockeel, T. J. (2014b). Aloina aloides. In T. J. Blockeel, S. Bosanquet, M. Hill, & C. Preston (Eds), Atlas of British and Irish Bryophytes (Vol. 2). Pisces Publications.
British and Irish Bryological Society. (n.d.). Aloina aloides. British and Irish Bryological Society. British Bryological Society. https://www.britishbryologicalsociety.org.uk/learning/species-finder/aloina-aloides/
Callaghan, D. A. (2022). A new IUCN Red List of the bryophytes of Britain, 2023. Journal of Bryology, 44(4), 271–389. https://doi.org/10.1080/03736687.2023.2185393
Campisi, P., Cogoni, A., Garcia, C., Hodgetts, N., Kucera, J., Lara, F., Lüth, M. & Schröck, C. 2019. Aloina rigida (Europe assessment). The IUCN Red List of Threatened Species 2019: e.T84534742A87771596. Accessed on 15 September 2026.
Hill, M. O., Preston, C. D., Bosanquet, S. D. S., & Roy, D. B. (2017). BRYOATT - Attributes of British and Irish Mosses, Liverworts and Hornworts. Centre for Ecology and Hydrology.
Hodgetts, N., & Lockhart, N. (2020). Checklist and country status of European bryophytes – update 2020. National Parks and Wildlife Service.
Hodgetts, N., & Lockhart, N. (2025). Bryophytes (Mosses, Liverworts & Hornworts). Ireland Red List No. 14. National Parks and Wildlife Service, Department of Housing, Local Government and Heritage.
Hradílek, Z., Chlachula, J., & Nesterova, S. G. (2011). New bryophyte records from Kazakhstan. 21, 29–36.
Ignatov, M., Afonina, O., & Ignatova, E. (2006). Checklist of mosses of East Europe and North Asia. Arctoa, 15, 1–130. https://doi.org/10.15298/arctoa.15.01
Jiménez, S., Suárez, G. M., & Cabral, R. A. (2020). New records of mosses from the Dry Chaco forest of Santiago del Estero, Argentina. Boletín de La Sociedad Argentina de Botánica, 55(4), 1–10. https://doi.org/10.31055/1851.2372.v55.n4.30127
Pescott, O. (2016). Revised lists of nationally rare and scarce bryophytes for Britain. 115, 22–30.
Pilkington, S. (2010). Aloina brevirostris/rigida. In M. Lawley, I. Atherton, & S. Bosanquet (Eds), Mosses and liverworts of Britain and Ireland: A field guide (First Edition, p. 471). British Bryological Society.
Written By: Lucy Hudson Last Updated: 21th September 2026