‘Drift fruits’ and ‘Drift seeds’


The fruits and seeds of tropical plants occasionally wash up on Irish beaches.  This phenomenon was first documented in detail by Nathaniel Colgan (1919) who showed that eight different species had been found here.  Donegal Bay was very poorly represented with only one specimen of the Sea Heart (Entada gigas) and one Blister Pod (Sacoglottis amazonica) being recorded.  Both were found by Amy Warren who lived on the Sligo shore of the Moy Estuary but apparently she found them on Bartragh Island which lies across the river channel in County Mayo.  Technically there were no records for County Sligo but because the waters of the Moy Estuary and Killala Bay are shared by the two counties they are herein considered as ‘honorary’ records for Sligo!

Charles Nelson who once worked in the Dublin Botanic Gardens, was next to summarise the Irish data (Nelson 1978).  He added Coconut (Cocos nucifera) to the list and also drew a map to show the approximate distribution of records around the island’s shores.  The Blister Pod of Amy Warren at Killala Bay remains the only Irish record for the species; and the Sea Heart is now shown as one from Kilalla Bay (presumably Warren’s record), two records from near Ballysadare Bay, and one from the Mullaghmore area.  Nelson drew attention to the apparent dearth of records from Donegal Bay and considered that the run of local currents might be preventing drift to freely enter the bay.

One more species was added to the Irish list by Nelson in 1982 and there have been a small number of notes published recording more Sea Hearts, but none from Donegal Bay.  The only mention of a drift seed from this region is of the Sea Pea (Lathyrus japonicus) which was found at Bunduff Strand and at Ballysadare Beach (probably Culleenamore Strand Ballysadare Bay) (Minchin & Minchin 1996).

The most recent publication of relevance to Donegal Bay is a book on the topic of tropical drift fruits and seeds (Nelson 2000) which incorporates and summarises all Irish data but adds nothing new for this area.

The following drift fruits and seeds have been recorded from the Sligo coast (none have yet been recorded from the coast of Leitrim).  A map of the locations of the beaches can be found here (click on this link).

Cocos nucifera (Coconut)

The Coconut is one very large and familiar species that I have seen washed up in Sligo on 10 occasions between 1992 and 2015.  On talking to some elderly local people it would seem that stranded coconuts were quite a familiar sight back in the 1950‘s and 1960‘s but went undocumented.  There is quite a lot of literature that discusses the provenance of drift coconuts with some authors believing they are all genuine long distance drift from tropical regions and others saying that they have either fallen off ships or have found their way into the sea from local sources.  Most people interested in this question take a middle route and consider that both sources of coconuts are likely.  It is possible to get clues to the likely origin of a specimen by close examination of the husk or shell.  For example the two photographs shown directly below are of a broken specimen found on Ballyconnell Strand on 16 July 2000 that is so small that it would have had no economic value and so it did not originate from a local shop!  The next two photographs are of a slightly larger intact specimen that I believe is also too small to be of a local origin.  The lower photographs of a specimen that has an intact husk that has been bored into by marine bivalves during its long passage across the Atlantic is more typical of the coconuts found washed up in Sligo and is clearly a long distance drifter.  The most likely origin of these coconuts is from the Caribbean.  The final specimen has an intact husk that has not been bored into and it looks suspiciously fresh!  This is most likely to have been discarded or lost locally.

Entada gigas (Sea Bean or Sea Heart)

This is probably the most frequent species found along the Sligo coast, possibly because it is large and quite obvious.  It comes from the Caribbean where it grows in Central American rain forests such as those that grow locally on Cuba.  This seed grows in a long pod similar to a giant bean pod.  The parent plant is a liana of the pea family that climbs up tall trees.  Just because this seed is the most frequently found doesn’t make it common and many beachcombers would be delighted to find one.  I have data for only 13 having been collected locally, 9 in the 1990’s and three in 2005; but I have anecdotal information of more being found but not reported.

Mucuna species (Horse-eye Beans; Hamburger Beans)

These are a real prize of beachcombers because they are both uncommon and beautiful.  They are members of the pea family and grow as a liana in the tropical rain forests of Central America where the flowers are bat pollinated.  I know of 8 having been collected on Sligo beaches and of 1 from Co. Donegal.  One of the Sligo Mucuna and the Donegal specimen are currently not available to me.  With the remaining 7 all lined up together, and using the guidelines in Sullivan and Williams (2008), I believe that 1 and possibly 2 are of Mucuna urens (the possible one is shown directly below); Mucuna sloanei (4 specimens) and Mucuna elliptica (1 specimen).

unidentified fruit endocarp

Looking at photographs on the internet the only match seems to be the endocarp of the fruit of Sea Coconut but this is not what it is because of the irregular shape and the distinctive surface texture.  The amazing thing is that it was found at the same place (within a few meters) and on the same date as the Calaba tree endocarp shown above i.e. Trawalua Strand, County Sligo on 13 March 1993.  Another relevant piece of information is that several specimens of sea coconut endocarp were collected from Great Britain “within a short period during the early 1990’s” (Nelson 2000) so this period seems to have been when unusual drift seeds were found in Europe.

In addition to seeds and fruits of a tropical origin it is common to find the fruits of hazelnuts and horse-chestnut (conkers) that are blackened by their long immersion in sea water.  These often raise the hope of having found something from more distant shores.  Other local fruits and seeds include beech husks and seeds, ash ‘keys’, alder cones, hawthorn berries, blackthorn and snowberries.  A newly published book touches on drift seeds and is excellent for anyone interested in beachcombing (Trewhella and Hatcher (2015)

Calophyllum species (Calaba Tree)

Only one specimen of this genus has been found in Europe prior to the one shown below.  This first record was found in about 1900 on the Isle of Barra, Outer Hebrides, Scotland by William McGillivray.  The record of Calophyllum was never published as he probably didn’t know what it was, but his collection of tropical drift seeds was donated to University of Aberdeen where the significance of his specimen was eventually recognised.

My specimen was collected from Trawalua Strand, County Sligo on 13 March 1993.  I had shown it to several people with an interest in oceanic drift without any successful identification.  Originally I thought it might be a gall rather than a fruit or seed.  It was only in 2012 when I saw photographs on an internet web site for Florida drift seeds that I realised it was the endocarp of the fruit of a species of Calaba tree and only the second record for Europe.  The specimen remains in my collection but will be donated to the herbarium of the National Botanic Gardens (DBN).

This genus of trees and shrubs grows over a wide range of tropical countries including places in the Caribbean.  Its fruits can fall into the sea and the inner part known as the endocarp can drift to many places around the world including the Atlantic coast of North America and clearly can also make it across the Atlantic to Europe.

Ipomoea species B

Collected at Trawgar Beach, Streedagh on 19 August 1993.  The photographs shown below are of the same specimen.  So far it remains unidentified.

Caesalpinia bonduc (Grey Nickernut)

There are three records of this species from County Sligo.  All were found by members of the Dick family on their local beaches in west Sligo (Dunmoran Strand and Tra Bui (Trawwee on the Ordnance Survey map)).

The frequent occurrence of this species along western European shores including Ireland means that the finding of this seed on the Sligo shores of Donegal Bay is long overdue.  I am still striving to find my first specimen!  The photograph shown below on the right has Rough Gooseneck Barnacles (Lepas pectinata) attached which is an indication that it had been at sea for a considerable length of time.

Blackthorn (Prunus spinosa)

This was an ‘unknown woody drift seed’ to me until Gerhard Cadee in The Netherlands suggested it was a Prunus sp. of local origin.  He was so right, as it is a Blackthorn (also called Sloe) just like the ones growing in my own garden!

Ipomoea species A

Three identical specimens were collected from Yellow Strand, County Sligo on 30 November 2015.  The photographs shown below are of the same specimen.

Lathyrus japonicus (Sea Pea)

There are records of Lathyrus japonicus for County Sligo at Bunduff Strand and at Ballysadare Beach (presumably Culleenamore, Ballysadare Bay) (Minchin & Minchin 1996).  Details of date, grid reference or observers were not published.  I am cheating here because the two views of the seed shown below is of a specimen found by myself on Trawmore Strand, Rossbeg in County Donegal and outside of Donegal Bay!  I am not absolutely certain that this is L. japonicus.

Sea Bean (Entada gigas)

with a Smooth Gooseneck Barnacle (Lepas anatifera) attached

Specimen found by Jean Dunleavy at Yellow Strand on 22 November 2015

Sea Purse (Dioclea cf. reflexa)

with Rough Gooseneck Barnacles (Lepas pectinata) attached

Specimen collected and photographed by Aoife Hegarty at Trawalua Strand on 22 November 2015

Dioclea cf. reflexa (Sea Purse)

The Sea Purse is less common than Horse-eye Beans.  So far there is only one record for Donegal Bay which was found at Trawalua Strand, County Sligo on 22 November 2015 by Aoife Hegarty.  There are several characteristic features including the thickness of the hilum (the black band around the edge) which is less than 2 mm and the shape of the seed which is not a regular round shape but is distorted with one edge more straight.

Sea Purse (Dioclea cf. reflexa)

Specimen collected by Aoife Hegarty at Trawalua Strand on 22 November 2015

Sea purse Dioclea cf. reflexa (on left) and

Horse-eye Beans Mucana cf. urens (in middle) and  Mucuna cf. elliptica (on right)

Note : Dioclea is darker in colour and that the hilum (dark band around edge) is much more narrow.

Grey Nickernut (Caesalpinia bonduc)

Found at Dunmoran Strand on 22 November 2015 by John Mark Dick

Grey Nickernut (Caesalpinia bonduc)

with Rough Gooseneck Barnacles (Lepas pectinata) attached

Found at Dunmoran Strand on 22 November 2015 by John Mark Dick

Full microscope scale is 1 cm

Full microscope scale is 1 cm

Full microscope scale is 1 cm

Full microscope scale is 1 cm

Top : Horse-chestnut and Hazelnut

Bottom : Alder; Beech husk and Beech nut

Found at Trawalua Strand, County Sligo on 13 March 1993 by Don Cotton

Found at Trawalua Strand, County Sligo on 13 March 1993 by Don Cotton

Blackthorn (Prunus spinosa)

of local origin

unidentified fruit

This small fruit still has a twig attached indicating it is a fruit rather than a seed.  It is very hard and black in colour.  The most significant feature seems to be the three small depressions at the base that are very similar to those of the coconut and are something associated with the palm trees.  Collected at Lissadell Strand on 08 January 2016 by Jean Dunleavy and Don Cotton

Ipomoea alba (Moonflower)

Collected at Trawmore Strand, Co. Donegal on 27 August 1993 by Don Cotton.


Colgan, N. (1919)  On the occurrence of tropical drift seeds on the Irish Atlantic coasts.  Proceedings of the Royal Irish Academy 35B(3):29-54.

Minchin, D. & C. Minchin (1996)  The sea-pea Lathyrus japonicus Willd. in Ireland, and an addition to the flora of West Cork (H3) and Wexford (H12).  Irish Naturalists' Journal 25(5):165-169.

Nelson, E.C. (1978)  Tropical drift fruits and seeds on coasts in the British Isles and western Europe, 1.  Irish beaches.  Watsonia 12:103-112.

Nelson, E.C. (1982) .  Tropical drift fruits and seeds - a new Irish species.  Irish Naturalists' Journal 20(10):452.

Nelson, E.C. (2000)  Sea beans and nickar nuts.  A handbook of exotic seeds and fruits stranded on beaches in north-western Europe. BSBI Handbook No. 10.  Botanical Society of the British Isles, London.

Sullivan, G. & J. Williams (2008)  Smiley.  Mucuna vs. Dioclea and Mucuna sloanei vs. Mucuna urensThe Drifting Seed 14(1):2-4.

Sullivan, C.J.; J. Williams & G. Sullivan (2008)  A world of drift seeds.  The Drifting Seed 14(2):5-10.

Sullivan, C.J.; J. Williams & G. Sullivan (2010)  A world of drift seeds.  Update 2010.  The Drifting Seed 16(2):2-3.

Trewhella, S. & J. Hatcher (2015)  The Essential Guide to Beachcombing and the Strandline.  Wild Nature Press, Plymouth.

Unidentified woody seed

Found on Bunduff Strand on 21 December 2015 by Jean Dunleavy and Don Cotton.

Mucuna cf. urens ?