ESSEX   BOTANY   AND   MYCOLOGY  GROUPS 

The status and distribution of Crested Cow-wheat Melampyrum cristatum L. in Britain, now largely

confined to Essex.

 Ken Adams

Essex Naturalist 2008. 25.120-127

 The Crested Cow-wheat is a summer annual that has undergone a catastrophic decline in this country over the last two decades, due largely to the flailing of road verges, and more recently arable field margins, during the flowering period, thus preventing seed production; and unless some drastic action is taken it is likely to become extinct within ten years. The past and present distribution of this spectacular plant in Britain is reviewed here at the 1km square level of recording. The bulk of the remaining British population now survives on just a few road verges and field margins in N W Essex, so unless we in Essex respond rapidly to the crisis, Crested Cow-wheat will join that other spectacular Essex speciality, Field Cow-wheat Melampyrum arvense, already lost to the county by a bungled conservation effort.

 Introduction

 Until the 1970s we had growing in Essex three of the four British species of Cow-wheat. It was the discovery of a population of the spectacular Purple or Field Cow-wheat at Bartholomew’s Green near Felsted, that led to my becoming involved with Stanley Jermyn and his Essex Flora project (Adams 1998). All the Cow-wheats are semi-(or hemi-) parasitic on other plants, Field Cow-wheat specializing in grass parasitism, and in particular when it gets a chance, wheat crops. It was once so abundant in some places in southern England including Essex, that its grains tainted the wheat flour and it had to be hand rogued. The name Melampyrum is a latin amalgam of ‘melos’ black, and ‘pyros’ wheat, from the early observation that bread made with contaminated flour turned black. At Bartholomew’s Green, where there were around 200 plants in 1959, the farmer told us that its local name was ‘mock-wheat’ due to the uncanny resemblance of its seed to a wheat grain. Until the development of grain cleaning equipment that relied on the different density of crop contaminant seeds for their separation, it was impossible to otherwise remove it from the fields. The resemblance of the seed of M. arvense to a wheat grain however, would appear to be fortuitous, as Melampyrum species have co-evolved their seeds to resemble the cocoons of ants. In the case of M. pratense,‘Common’ or Meadow Cow-wheat, (alas no longer common) which grows in woodland on acid soils, dispersal is aided by wood ants which collect the seeds so efficiently that their other competitors, small rodents, hardly get a look in (Gibson 1993). Extrafloral nectaries, in the form of glandular hairs on the upper leaves and bracts, exude sugary droplets that attract the ants, and as soon as the capsules open, they creep in and extract the seeds and wisk them off to their nests. In addition to resembling ant cocoons, even changing colour from white to dark brown as they age, the seeds have a hemispherical sweet tasting lobe at one end known as an oil body, caruncle or elaiosome, a further attraction to ants, which take the seeds to their nest and feed the elaiosomes to their larvae.

After the larvae have consumed the elaiosomes, the ants take the seeds to their waste disposal area, which is rich in nutrients from the ant frass and dead bodies, where the seeds germinate (Fischer2004). Thus by co-evolving with ants, Melampyrum species have developed a rapid means of getting their large seeds below ground out of the way of foraging rodents, and into a well aerated, friable seed bed - the ants also aid in dispersal as the seeds are heavy, and but for the ants would not spread much more than 25cm away from a parent plant.

Fig. 1. Seeds of Crested Cow-wheat.

They are collected out of their capsules by ants, and taken to their nests where the larvae are fed the oily white hemispherical elaiosomes, and the seeds are then dumped in their frass midden, thus burying them deep in a dry, friable soil ready for germination the following year. © Ken Adams. 

In M. cristatum the seeds are produced in batches of four per capsule, though not all four necessarily develop fully, and being heavy drop suddenly from the plant. Interestingly, when watching seed drop, it seems obvious that the crested bracts, which are channelled, have evolved as chutes, rather like a child’s playground slide, so that the heavy seeds are shot out sideways rather than dropping like stones to the base of the plant. Moreover the inflorescence is a dense 4-sided spike, so that the seeds are shot out in all four different directions. In contrast, only two seeds are produced per capsule in M. arvense, and the bracts do not appear to intervene in seed drop. Perhaps not surprising in a plant that has probably coevolved to parasitize human grain crops, its best chance of survival being to stay put. By adapting for ant dispersal the genus Melampyrum has been able to produce the largest heaviest seeds in the Scrophulariaceae. M. pratense is a plant of acid woodland clearings and heathland, and forms haustoria with a variety of woody hosts. Cattle were also originally woodland animals, and early domestic cattle were largely fed on tree shreddings. Both cattle and sheep avidly consume the plant and pigs will consume the seeds. When cattle ate M. pratense it was noted that the butter was much richer in colour (due to flavonoids), and Linnaeus stated ‘that when cows are fed in fields where the Meadow Cow-wheat is abundant, the butter yielded by their milk is peculiarly rich and of a brilliant yellow colour’. Hence the origin of the common name ‘cow’-wheat. The origin of the name ‘wheat’ is said to be derived from a belief in the Middle Ages that the seeds were capable of being converted into wheat, quite believable, if one reads the Rev. Gilbert White’s account in the Natural History of Selborne (1867) of the strange beliefs about the origins of birds and insects still around among country folk in his day; and not unreasonable if dormant Cow-wheat seed suddenly gave rise to Cow-wheat among corn crops in cleared woodland. I would think it even more likely that this story has been turned on its head over the years, and that seeing the resemblance of the seeds to wheat, folk believed that some of their seed corn morphed into Melampyrum, no doubt in divine retribution for some misdemeanor! Although the elaeosome tastes sweet, the seeds themselves are bitter, and according to the physician and botanist Rembert Dodonaeus (1550s) ‘the seeds of this herb taken in meate or drinke troubleth the braynes, causing headache and drunkennesse’.

Distribution Patterns

 The Field Cow-wheat and the Crested Cow-wheat are obviously very closely related to each other, their seeds are virtually identical, they are both summer annuals, their flowers and bracts are very similar, and they can both parasitize grasses, although M. cristatum is also able to form haustoria with shrubby species. To form an effective coupling to a host, M. arvense seeds need to germinate at about the same time as the host, (attempts experimentally to get them to couple to mature hosts generally resulting in failure), this may not however, apply to the shrubby species that M. cristatum prefers. Both however, need to be able to germinate, grow, flower and set seed before the autumn. Whereas M. arvense appears to have evolved largely as a weed of corn fields, and in Britain is generally regarded as most likely to have been been introduced as an imported grain contaminant, M. cristatum would appear to be a native species which originally inhabited scrubby grassland on freely draining calcareous clay soils. Its past and present recorded distribution is however difficultto decifer. Because it can parasitize grasses as well as shrubs, as in the case of M. arvense, some of the many old records scattered across southern England could have resulted from short-lived introductions as a crop seed contaminant. This would account for the otherwise extraordinarily concentrated distribution pattern which the bulk of the past and present records reveal. These as the maps Figs. 2 & 3 show are concentrated in a band that runs diagonally across north Hertfordshire, through north-west Essex across to mid-Suffolk and then north to Norfolk, with a major outlier extending north westwards from Cambridgeshire towards Bedfordshire and Leicestershire, and north to Lincolnshire. The Sulphur Clover has a somewhat similar distribution pattern (Adams 2007), but that has a wider band of distribution more or less following the Hanslope association soils of the more calcareous facies of the glacial till known as the Chalky Boulder Clay. The Crested Cow-wheat is also largely confined to the chalky boulder clay (CBC), but its distribution also coincides with the crest of the East Anglian Heights, its occurrences being just over the crest on the dip slope of the hills, the diagonal running perpendicular to the valleys carved into the chalky boulder clay since the last ice age. This suggest that the bulk of the UK population is confined to the steeper and most freely draining segments of the CBC on slopes that dip gently to the SE and are therefore largely protected from cold winds from the north, and being inclined to the sun will receive a greater level of insolation. In contrast the Sulphur Clover appears to prefer the less freely draining plateau slopes further south. This pattern does not apply to all the Crested Cow-wheat colonies however. Quite a concentration of populations in former times occurred to the north west of the ridge, although again probably always on chalky till deposits. A possibility here is that in mild years with hot summers, Crested Cow-wheat can do well on less sloping ground as long as the spots are protected from the northerly winds and are open to the sun, but that its fall back core population is able to survive even the coldest of years on the better lit slopes of the ridge. Yet another possible interpretation however, is that in the past Crested Cow-wheat was much more widespread and has contracted to its present range because it has up until now been less persecuted by agricultural developments, including the removal of hedges and the lack of management of woods. It is important to realise that our woodlands until about 200 years ago were intensively exploited for fuel and construction materials, coppicing was widespread and grasslands were lightly grazed, leading to a mosaic of scrubby grasslands in which vulnerable annuals could be assured of completing seed set without being flailed, and arable land was in the minority. Would we could get into a time machine and go back to the days when in 1660 John Ray penned the comment about its distribution in south Cambs: ‘in Madingley and Kingston woods, and almost all woods in this County plentifully, likewise it overspreads the pasture or common grounds you ride through going out of Madingley to Dry Daiton’; he also commented that it was common in Bedfordshire woods. In such a mosaic landscape several species of ant would have been abundant and could well have served to spread the seeds to all possible niches. Although on the continent Lasius flavus (Yellow Meadow Ant) has been observed carrying off M.cristatum seeds, there do not appear to be any observations of it happening in this country, and it is certainly doubtful if this species of ant is at all plentiful in the agricultural desert of modern N W Essex. There is clearly some room for us to do some field observations on our M. cristatum plants at seed drop time.

We are fortunate in having a Journal of Ecology Biological Flora article devoted to M. cristatum (Horrill 1958) and I quote some of his observations here. Although M. cristatum is capable of photosynthesis, experimentally germinated seedlings die at an early stage unless they can form a host connection. The full host species range is not known, but it does not seem to be very specific as experimentally it has been known to form haustoria with the grasses Poa annua, Lolium perenne, and Deschampsia cespitosa, the clovers Trifolium repens and T. pratense and the woody species Ligustrum vulgare and Rubus fruticosus. Seed stored in dry soil rotted, but if stored in moist soil or sand, radicles appeared after being given a 4-week cold treatment in the dark, but germination was only completed if the cold period was extended to 8 weeks. Not all the viable seed germinates, and some can remain dormant for at least two years. George Gibson in his Flora of Essex (1862) says of M. cristatum, ‘this showy plant quite takes the place of M. pratense in the N W of Essex, especially near Walden. It grows in shady hedges, and often covers the ground in woods, the year after the underwood has been cut’. Just how long it can remain dormant appears to be unknown, but it must be at least 10-15 years from our own observations over the years at Little Hales Wood. When I visited the wood with Stanley Jermyn in the late 1960s it had appeared in abundance following coppicing at the southern end, and it has reappeared there again after recent coppicing. This is in contrast to M. arvense which is said germinate in the autumn and overwinter as a rooted seed, not producing a shoot until the spring, and has a very limited viability of around two years. The common denominator in the distribution of M. cristatum, seems to be an association with oak woodland, but it is rather a plant of open rides and woodland margins, and seems to benefit from clearance of competing vegetation as much as letting in the light. Its most likely primary habitat in the past was probably scrubby grassland around the edges of woods. Another very local plant with us in Essex, Greater Burnet saxifrage Pimpinella major has a similar preference for old woodland rides, and old woodland edge verges on calcareous soils. Apart from its stronghold in the N W of Essex,

Figures 2 and 3 show the recorded occurrences of the now very rare Crested Cow-wheat Melampyum cristatum in Eastern England, showing its preference for the Chalky Boulder Clay (Fig. 2), on the well drained crest and upper dip slopes (Fig. 3) of the East Anglian Heights. Filled circles post 1990 (all known UK records), open circles not recorded since 1990; at the 1km sq. level. Note that for old poorly localized records some circles may be on the intersect between two or four 1km sqs. 

Fig. 2. Crested Cow-wheat Melampyum cristatum in Eastern England, showing Chalky Boulder Clay. Hand traced from: Quaternary Map of the U.K. South. Crown copyright reserved.

Crested Cow-wheat grew in the past in woods (plural) near Gestingthorpe in 1724 (Samuel Dale), where it would have been on chalky boulder clay, and it was seen in Hazeleigh Wood, Maldon in 1886 on an EFC meeting. It does not grow in Hockley Woods! (Essex Birding 2008!). There was also a population way down in S. Essex in a meadow near Beckney Wood, found by R. Glover in 1972, growing with Orchis morio and Dactylorhiza fuchsii. Overgrazing and the use of the meadow for pony jumping destroyed it shortly after 1980 when Roger Payne found just a single plant. There seems to be no evidence of involvement of mycorrhizal fungi and it has been successfully introduced as seed to the Blacklands N.R. in Northants by Natural England. In Germany, experiments with M. pratense on acid soils in mixed woodland where Melampyrum was initially absent, using 300 seeds/m2 plot inoculations, resulted in successful establishment, and a mean rate of expansion of 0.9m per year with some patches expanding (with the help of ants) to 6.5m/year (Heinken 2004).

Fig. 3. Crested Cow-wheat Melampyum cristatum in Eastern England, showing height contours: less than 0m, 0-50m, 50-100m, 100-150m, 150-200m.

In contrast, attempts to expand a natural population on behalf of the Heath Fritillary at Blean Woods RSPB reserve in Kent (Walter 2005) met in failure, most likely because the seedlings failed to establish haustoria. The majority of our Essex populations of Crested Cow-wheat are now on road verges. In this habitat, disturbance, such as pipe laying or trenching, exposing top soil, stimulates development – presumably due to lessening of competition, but it competes fairly well in quite tall vegetation. Following germination at the end of February/early March it can withstand light frosts, but needs to establish haustorial connections and complete its growth between April and May, and if flailed just once early in May, can sprout new flowering shoots providing the flail does not rip up the plants altogether. If flailed a second time in July the plants are killed. An early June drought can cause quite severe wilting. Flowering occurs from June to October with the first crop of seed around mid-July. By the first frosts of autumn the plants are already dead. Cross pollination is by bumble bees, and if this has not taken place by 4-7 days after becoming receptive the stamens bend round to effect self-pollination. No vegetative reproduction is possible, and being a summer annual or therophyte, if the plants are killed before seed set, regeneration the following year is dependent on the 15-40% of dormant seed that perenates over from the previous year. It is apparent from visiting a range of successful patches, that in virtually all cases the spots are sun traps protected from northerly winds. Just over the brow of a hill, or on the southern margin of a wood or hedge. Similarly on the continent where it ranges south to the Pyrenees, north east Italy and Albania, and east to the Urals. It is absent from the low countries and immediately south of the Baltic, but extends north to Denmark and southern Sweden. Everywhere it is a thermophile needing open sunny sites on south facing slopes experiencing temperatures between the limits of the 15.5^o C July and the 10^oC January mean monthly isotherms. It grows on a range of clayey, alluvial and sandy calcareous soils, but needs a certain amount of humus, not being found on skeletal/mineral soils over chalk and limestone, although it formerly grew on soils over limestone in Rutland. Of the surviving populations only a single native site is left in Northants, on a verge opposite Southey Wood, where according to Rob Wilson, it was flailed out of existence this year apart from a small patch where a tree obstructed the flail, and is unlikely to survive in the future. In Bedfordshire, again Chris Boon informs me that only a single site is left, on a road verge at Honeydon, where it varies in abundance from just a few to a 15x3m patch. In Hertfordshire it was deemed extinct, but this year Trevor James tells me that an old site near Nuthamstead produced plants, when the edge of an arable field abutting a wood was allowed to developed into a strip of grass. In Huntingdonshire a small patch survives along the south west margin of Monks Wood and at a second site on verges both sides of Stocking lane where Cambs.C.C. manage it sympathetically and a large population survives. In West Norfolk it now survives precariously at just one site on a verge at Beetley. West Suffolk and Cambridgeshire fair rather better with post-1990 populations surviving at around six sites and nine sites respectively. There do not seem to be any post-1990 survivals in either Leicestershire or Lincolnshire. Nearly everywhere the woodland populations have gone due to the lack of coppicing, field margin sites have been lost with conversion of grassland to arable, and road verges are now flailed in mid summer. In Essex we have populations surviving at around 12 known sites, some quite extensive, and we need to do a systematic re-survey of sites that have not been visited for some years. Management of verge sites is largely by way of Special Verge status by arrangement with local farmers, but ‘accidental’ flailing in the fatal July period by council flails is still a frequent occurrence, and in recent years flailing around the inside of arable fields before harvest is having a devastating effect on our arable field margin populations, and as elsewhere, patches are exterminated year on year. With in some cases crazy situations where wildlife strips are left and sown with ‘wild flower’ mixes for the birds rather than encouraging our local rarities. I propose to approach local farmers and wood owners in the area of its distribution in the hope of coming up with a coordinated strategy to protect and manage sympathetically the non-verge populations we have left, and to introduce seed back onto old sites where its survival can be enthusiastically guaranteed.

Acknowledgements

I am indebted to our BSBI Vice county recorders for supplying comments at short notice, to Alex Lockton for the BSBI database file of U.K. localities, to our dedicated team of verge reps who keep tabs on our Essex populations year on year, and to Peter Allen for the loan of the geology maps.

References

ADAMS, K.J. (1998) The Third Essex Flora and BSBI Atlas 2000 Projects: An historical perspective. EssexNaturalist 15: (New series) 57-59.

ADAMS, K.J. (2007) Notes on Essex Specialities 12: the status and distribution of Sulphur clover, Trifolium ochroleucon Hudson in Essex and eastern England. Essex Naturalist (New series) 24: 115-118

FISCHER, E. (2004) The Families and Genera of Vascular Plants. Vol: 6 p.344. Springer.

CROMPTON, G. (2008) Cambridgeshire Flora records since 1538. Part 1 & 2. Current web site: http://mnlg.com

GIBSON, G.S. (1862) Gibson’s Flora of Essex. William Pamplin. London.

GIBSON, W. (1993) Selective advantages to hemi-parasitic annuals, genus Melampyrum, of a seed dispersal mutualism involving ants. II. Seed predator avoidance. Oikos 67: 345-350.

GRIEVE M. (1931) A modern herbal. Available on line at: http:www.botanical.com

HEINKEN, T. (2004) Migration of an annual myrmechore: a four year experiment with Melampyrum pratense L. Vegetatio. 30: (1) 55-72. Springer.

HORRILL, A.D. (1972) Biological Flora of the British Isles. Melampyrum cristatum. J. of Ecology 60: 235-244.

WALTER M. (2005) Transplanting and sowing seed of common cow-wheat Melampyrum pratense toincrease its distribution at Blean Woods, RSPB Reserve, Kent England. Conservation Evidence 2: 41-42.