taxonomy Two UK Gladiolus Anthony Hamilton discusses the status of naturalized ‘Byzantine’ gladiolus, also common in gardens, and a ‘native species’ found in the New Forest

here are two taxa of Gladiolus that can be found Tin the ‘wild’ in the UK. Gladiolus communis subsp. byzantinus is an introduction from Mediterran­ ean countries that is widely grown in gardens and naturalized on rough ground, particularly in the southwest. Gladiolus illyricus is reputedly native and found only in the New Forest in south Hampshire (it also occurs in Europe). This article is based on ideas I originally disseminated at a one- day conference on the New Forest Gladiolus co-organized by the Botanical Society of the British Isles in March 2010. The ideas were further amplified at a symposium in South Africa organized by the Indigenous Bulb Association of South Africa in August 2011. In this article I shall examine the status of these two taxa and demonstrate that both are clones, and that G. illyricus is also naturalized and not native.

Background Gladiolus is a large genus of around 270 species of African origin. Its centre of diversity is at the Cape where it has its lowest chromosome numbers. The diploid number there is 2n=30 (the basic number being x=15 for the genus). The chromosome number of the different species increases to Common in gardens in southern England, Gladiolus communis subsp. byzantinus has also escaped on

Andrew Lawson Andrew to waste ground and roadsides

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Restricted to the New Forest in the UK,Gladiolus illyricus is often hidden under bracken and difficult to find The flowers ofGladiolus illyricus tetraploid 2n=60 as you progress several new features have evolved, but distinctive, unwinged, pellet-like north up the continent. in the context of this investigation it seeds. Flower colour in most Beyond mainland Africa, Gladiolus is the unwinged seeds which are European Gladiolus is so similar, are found in Madagascar, the notable. This character­ is not usually variations of magenta, so Arabian Peninsula, the Middle East exclusive to G. italicus and a handful other floral characters must be used and around the Black and Caspian of related species found in the same for identification. Seas. They are also found around the geographical area, the so-called A different group of Eurasian Mediterranean, including North Fertile Crescent, share the tetraploid species has winged seeds Africa, where the genus has evolved condition. This is the area where – this is the usual method of dispersal a new centre of diversity, very much humans first selected important throughout­ the genus. Of these based on an increase in chromosome grain crops, such as wheat, from species, G. illyricus is one of the most number, doubling to octoploid wild grasses. As grain crops were common in Western Europe and is 2n=120, but not exclusively. progressively improved, especially in found through Portugal and Spain However, perhaps not surprisingly size, over the millennia, the seeds of to France, and debatably to England. for such a large genus covering such weedy Gladiolus species evolved to Gladiolus communis also belongs to an enormous geographical area, it match their size so they would be this group. has evolved frost resistance as the harvested and sown with the grain species enter Europe. The most crop. In addition to human-aided Gladiolus communis subsp. northerly populations of the genus dispersal, unwinged Gladiolus seeds byzantinus are found in the Baltic, principally are transported and effectively This is the plant that used to be around the Gulf of Finland from ‘sown’ by ants, which are attracted to known as Miller’s Gladiolus Helsinki to the Saint Petersburg area. the elaiosome (oily food body on the byzantinus (he coined the name at The two commonest species, surface of the seed). Gladiolus species level in 1768). It is common G. communis (excluding subsp. communis has often been confused in gardens in southern England byzantinus) and G. italicus, both have with G. italicus. However, G. italicus where it spreads readily and often 2n=120. In the case of G. italicus has narrow, oblong, side tepals and escapes. If any plant can be called ➤

March 2013 51 taxonomy Stephen Mifsud Stephen Stephen Mifsud

Gladiolus communis on Malta (left), and, on the same island, a specimen ofG. communis (right) resembling its likely progenitor, G. illyricus the ‘British gladiolus’, it is this. It interior between the wings. These was a postgraduate student. I was does not appear to suffer from any seeds appear to be viable but the confused and did not know how to diseases, unlike every other gladiolus, germination rate is extremely poor handle it taxonomically. I therefore and appears immune to viruses. and most seedlings die within a few treated it as G. communis subsp. byz­ It has acquired its own mythology weeks. Those few that do survive antinus in Flora Europaea (Hamilton – namely that is is a wild taxon, it grow weakly and can linger on for 1968). That position is, I think, spreads by seed, and it comes from years, gradually deteriorating and incorrect and should be re-examined. Byzantium (an area centred on the never flowering. This is because I have managed to get a seedling ancient city of this name in north- of their chromosome number – from self-pollinated seed to flower. east Greece). These beliefs have G. communis subsp. byzantinus is It looked very much like G. illyricus, arisen from careless and casual hexaploid, 2n=90. This means that it which is what I would expect observation without any checking. will form gametes (pollen and ovules) because I have always regarded that The first thing to notice is that the which have a range of different species to be the tetraploid flowers exhibit no significant chromosome numbers (aneuploid). progenitor of the octoploid variation – they are essentially the Because these are unable to form G. communis. The photograph (above same on every plant. balanced pairs of chromosomes in right) illustrates this point. Secondly, those who are untidy their subsequent seed, when self- It may seem strange, after what gardeners, like me, will know that pollinated, most will abort. This I have just written, but G. communis left to its own devices and not usually happens before the fertilized subsp. byzantinus has been used cleared away it will seemingly form a ovules even get to the seed stage. In experimentally in crosses with other few seed capsules in most years. functional terms it behaves like a garden Gladiolus. The pollen and However, if these are allowed to triploid – the chromosomes cannot ovules of G. communis subsp. progress to maturity a different story pair up, resulting in sterility. Hence byzantinus are aneuploid, but one of emerges. You will find a lot of chaff the poor seed-set. these gametes may have a full and a small number of seeds, but I initially pulled these observations compliment of the essential genes these do not have a healthy, plump together in the early 1960s when I (even if it also has some extra ones,

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byzantinus from UK gardens with 2010 the situation has improved. In corms of G. imbricatus from Saint the UK it is assumed to be native but Petersburg in Russia. I placed is currently restricted to the New unprotected corms on a bench in an Forest, although formerly occuring unheated greenhouse for several on the Isle of Wight (Stace 2010). weeks in mid winter during which It was also thought to spread by freezing temperatures frequently seed, just like the Continental forms, prevailed. The corms of G. communis and to be hardy in southern England. subsp. byzantinus rapidly succumbed Finding G. illyricus in the New to frost and the corms were reduced Forest is very difficult because it to pulp. In contrast, the corms of normally flowers under bracken G. imbricatus were unaffected. (Pteridium aquilinum) which both However, in the south of England, shelters it, hides it, and protects it plants that are growing in the ground from grazing. This is almost certainly are relatively frost resistant. The why it was not until Victorian times resting corms gain a degree of that it was first discovered in the protection from being buried UK, on the Isle of Wight. relatively deep. Also, the foliage is Indeed, the best way to monitor a frost-resistant and can be frosted non-flowering plant is to visit early in and snowed on with complete the year to spot the young leaves. Stephen Mifsud impunity. This may account for Then insert bamboo canes beside references in garden literature the emerging foliage, using short suggesting G. communis subsp. ones so as not to draw attention to byzantinus is hardier than it is. the plants, and return on a regular White Gladiolus communis has garden potential The final question to answer is basis to watch progress. You also which will be superfluous). If that the geographic origin of G. communis need a detailed map or a GPS device, gamete meets a balanced gamete in a subsp. byzantinus. Despite Philip as it is easy to get lost in the New successful pollination from another Miller’s belief that it came from an Forest. Plants of flowering size will taxon, it will produce a cytologically area that includes west Turkey, bloom from the end of June to mid balanced seed. Bulgaria, Greece, Albania and the July, depending on the season. Any I have crossed G. communis subsp. former Yugoslavia, it has never been work that might disturb these prot­ byzantinus (the garden clone), as the found wild in those countries. Its ected plants needs to be licenced­ by female parent, with G. communis closest wild relatives can be found in Natural England. Fortunately, the which I collected from Gibraltar. north-west Africa, principally Forestry Commission is now clearing This produced a good collection of Morocco. There, richly coloured scrub around Gladiolus sites so it normal seed, even though the cross forms, principally dark red, of does not develop into forest, shade was 2n=90 x 2n=120. G. communis can be found, unlike out the plants, and lead to extinction. This leads to the question, if the paler coloured forms common Typical G. illyricus in continental G. communis subsp. byzantinus does in most of the Mediterranean. These Europe has a range of flower shapes not spread by seed which, even if are natural populations that spread and colour distribution in its tepals fertile, the young plants will be killed by seed. In my recent studies of this (see p54). This is exactly what one by frost, how does it spread? The species in the Maltese islands I have would expect from populations answer is by large cormlets produced found similarly coloured forms, reproducing from seed. It is when on deeply entrenched stolons. These including white ones (Mifsud & these Continental flowers are are then further distributed by Hamilton, in press). compared to English G. illyricus that human activity. one striking fact emerges. There is With regard to frost hardiness, Gladiolus illyricus no natural variation; all the flowers I tested Gladiolus corms to destruct­ We are fairly short of detailed of English G. illyricus are the same. ion when I was a postgraduate student knowledge of this species, especially They share this same lack of at Durham University. I compared its representatives in the UK. variation with G. communis subsp. corms of G. communis subsp. However, following a conference in byzantinus and is a vital clue as to ➤

March 2013 53 taxonomy what sort of plants they might be. mature corm which has been taken G. illyricus. Herbarium records The next thing to consider is over by its own cormlets. By of British-type G. illyricus on the chromosome number. Continental repetition of this process a colony Continent are few. Some have been G. illyricus is tetraploid (2n=60) but will gradually spread outwards. collected from Saumur and English G. illyricus is hexaploid There are now disjunct colonies Fontainebleau in France but no (2n=90) (Darlington & La Cour around the New Forest. I speculate recent living specimens have been 1960). I took my counts from plants that this distribution is the result of found there. Indeed, they would collected at Wilverley Walk in the old agricultural practices which naturally die out once forest climax New Forest, which yielded 2n=90. would have involved harvesting and conditions became dominant. A I suspect the same figure would be transport of the associate plant, more recent record has been made found in other New Forest colonies, bracken, which was mainly used for from Belle Île off the north-west but it would be prudent to examine animal bedding. Corms and cormlets coast of France, where the habitat is others. would have been pulled up during similar to the New Forest, but I have However, from what I have the harvesting and spread around. not been able to visit the population. found so far, it would appear that The avoidance of cold and It is not known how it reached G. communis subsp. byzantinus and continued survival of G. illyricus in England. I like to think that the G. illyricus are both semi-sterile the New Forest plant can be Romans brought it from the Contin­ hexaploids. accounted for by the corms and ent, although there is no evidence for Seed capsules on G. illyricus have cormlets being found fairly deep this. Perhaps a Roman gardener usually formed by September. They (7–8cm) in the soil and the insulating found it in France, admired its beauty, are usually somewhat sparse on the layer of bracken debris. and transferred it to a settlement in spike, often only two or three, which There has been much speculation southern England. The Romans might be assumed to be the result of on the origin of these English were also present on Belle Île! poor pollination conditions when the flowers were out in June and July. However, when the ripe capsule is opened one finds very few viable seeds and they are only partly winged. I have tried germinating them after exposure to cool conditions, as a sort of mild vernalization, but have not exposed them to frost. I have not been able to raise seedlings, and I am not aware of any other claims to have successfully done so. What appears to be happening with both G. illyricus and G. communis subsp. byzantinus is that at pollinat­ ion time, the pollen tube extends down the style. This is enought to stimulate, probably hormonally, later pod formation.However, when the pollen tube reaches the ovules, the mis-match of chromosome numbers results in seeds not forming or being

virtually sterile. Alex Lockton Alex Lockton Gladiolus illyricus spreads through the New Forest very slowly. The photograph (p55) shows a mature Spanish Gladiolus illyricus in the wild, where the flowers are variable in form and colour. plant and the site of a now dead One of the most noticeable differences is in tepal width, being either narrow (left) or wide (right).

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Conclusion These two taxa have previously been considered to be normal, wild representatives of the same group of Eurasian Gladiolus species. However, after careful examination they have been found to be clones that spread vegetatively and locally by cormlets. There is no evidence of any seed spread and their climatically mild and protected habitats ensure that these plants survive from year to year. Purely as a working position, I have coined the unpublished name G. illyricus “subsp. anglicus” for the English gladiolus while I have been studying it. This matches the existing subspecific treatment of G. communis subsp. byzantinus. However, their clonal status, that has now been clearly demonstrated in this work, mitigates against treating them as natural taxa which Jonathan Stokes the designation of subspecies would Gladiolus illyricus in the New Forest reproduces by dispersal of corms. The plant on the right has reached imply. The correct treatment that maturity and will flower. The smaller leaves on the left are growing from immature corms arising from the site of a mature corm that has flowered and died. should be given to them is cultivar status and this will be done, after references consultation, over the next few years. Darlington, CD & Le Coeur, LF University Press, Cambridge (1960) The Handling of Chromosomes. Mifsud, S & Hamilton, AP (in press) George Allen & Unwin Ltd, London Preliminary observations from long- Hamilton, AP (1968) Gladiolus L. term studies of the genus Gladiolus L. Anthony Hamilton was a In: Tutin TG, Heywood, VH, Burges, on the Maltese islands. The Central Senior Lecturer in Plant Sciences NA, Moore, DM, Valentine, DH, Mediterranean Naturalist at the University of East London. Walters, SM, Webb, DA, Chater, AO Stace, CA (2010) New Flora of the Now retired, he is a lifelong & Richardson, IBK (eds) Flora British Isles. Cambridge University Gladiolus enthusiast. Europaea. Vol. 5. Cambridge Press, Cambridge Stephen Mifsud Stephen Mifsud Stephen Mifsud

The two Gladiolus discussed in this article (G. communis and G. illyricus) have winged seeds, such as those ofG. communis (left). Other species, such as G. italicus (centre), have evolved unwinged seeds (right) to aid dispersal with grain crops.

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