Aliens - escapes!

Iver and District has long been BLESSED (or some may say, cursed) with more than its fair share of non-native species of plants. Druce, in FLORA OF BUCKINGHAMSHIRE (1926), paid a good deal of attention to what at the time he described as these 'ADVENTITIOUS' plants. He explained that the explanation for the very large number of them a century ago was, the proximity to what we now call GREATER LONDON. The chief factor being the immense quantity of street sweepings and house refuse which was brought from urban areas in barges and deposited on the banks of the canal or the adjacent brick-yards. In the brick-kilns, after the iron, glass and pottery was separated, the refuse was used as fuel. At that time the resultant strong nitrogenous 'soil' brought rank and profuse growth of CHENOPODIUM RUBRUM, variants of CHENOPODIUM ALBUM and ATRIPLEX spp. The brick-kilns are now long gone.

Given that ALIEN and ADVENTITIOUS plants still form such a conspicuous element of the local flora which surrounds me and through which I regularly walk and cycle, it seems a good idea to place them within a separate page of this web-site, contributing to a better understanding of which are 'native' and which are 'alien' species in the British Isles. The technical terminology applied to aliens divides them into ARCHAEOPHYTES and NEOPHYTES - the former having established themselves prior to 1500 (some sources give the date as 1492, the time of the voyages of Christopher Columbus), the latter since then.

Once again, best to arrange the entries in alphabetical order by genus and species.


I do not remember noticing any CONYZA species in the 1970s or 1980s. These have primarily been weeds of urban areas. Although I have lived in towns most of my life, my focus has, until the past year, very much been on natural habitats, such as remnants of woodland in Stevenage, Hertfordshire. At that time I paid minimal attention to the weeds found in streets. Had I come across any fleabanes, I would have assumed (like others have) they were CONYZA CANADENSIS, known as 'Canadian Fleabane'. This is the only species mentioned in 'Flora of the British Isles' - which was the standard reference work of that time. Had I noticed any 'atypical' examples, I would have put them down to variation within this species. But the situation has changed significantly and it is now clear that other taxa are present in the UK - though there is ALWAYS debate as to whether the variation is classified at variety, sub-species or species level. Crawley, in 'Flora of Berkshire, 2005' provides a key, stating that the 4 alien species of CONYZA are readily distinguished in the field. Whilst his key (presumably based upon Stace's 'New flora of the British Isles' which I MUST purchase) is helpful, I cannot but wonder if it really is that straightforward? As with all keys and descriptions, initially it can be difficult to understand what is meant by some of the terms and plants VARY.

Whilst searching for further information on the internet, I came across a pdf version of the Jan 2012 BSBI Bulletin (No. 89) CONYZA IN WALES - WE HAVEN'T BEEN PAYING ATTENTION! (see: The authors explained that whilst C.CANADENSIS had been known in the British Isles since 1690, other species are clearly present. It seems that many specimens which are in fact CONYZA FLORIBUNDA (Crawley uses the species name C.BILBAOANA rather than C.FLORIBUNDA, which he gives as a synonym) were previously mistakenly identified as CONYZA CANADENSIS. It is reassuring for us 'lesser' botanical figures, that the culprits included most of the top botanists in Wales! Another example of one "assuming" that a plant one glanced at, belongs to a 'commonly' encountered species; unless someone has been alerted to other possibilities (i.e. are actively "looking out for") them, this can easily happen. I am strongly in agreement with the article's concluding sentiments - this will not be the end of the CONYZA story.

The authors considered that it was abundantly clear that the taxonomy and systematics of the genus are very complicated and the extent to which any of them understood the species boundaries was limited - names and concepts are BOUND TO CHANGE. Even experienced and skilful plant taxonomists will interpret variation differently and often they are obliged to draw their conclusions based upon scant, poor quality material - when more and better material becomes available, their findings may change. The confusion is often compounded by inexperienced so-called 'botanists', jumping to false conclusions through incompetence. Botanists from different regions of the world are sometimes divided into "clumpers" and "splitters" - the latter all too readily assigning the samples in front of them into a 'new' species. In some countries this represents a short-cut to the 'fame' of having 'discovered' a new species of plant within that country. Whilst this may sound impressive on paper, especially to non-scientists (and politicians), it is a significant contributory factor in the major MUDDLE that often exists as to the naming/identification of species within a genus. In Britain, it is all too easy to assume that species names from other countries are equally valid/reliable to those which are assigned by British botanists. I know of very capable field botanists and plant taxonomists in Europe, North America and New Zealand but have legitimate concerns about the competence of those from many other countries.

There is not universal agreement as to the distinction between CONYZA SUMATRENSIS and CONYZA BONARIENSIS; it seems that Cronquist, the distinguished North American plant taxonomist, did not recognise CONYZA SUMATRENSIS as a distinct taxon, whilst Strother has NOT included it in a recent account of the genus in the 'Flora of North America'. Another example of something which ALL Scientists, not just those in the biological spheres, should never forget - the BEST anyone can say, provided the are well-informed, is to "the BEST of our present knowledge/understanding", mindful that this could change! It may seem natural to automatically accept/recognise the findings/what is published in a journal/flora but it ALWAYS makes sense to exhibit a healthy level of scepticism. We need people like Dr Ralph Stewart (flora of Pakistan and Kashmir) and myself, who combine field experience and general herbarium knowledge, capable of assessing the findings of others.

I consider it fair to say that I am one of a small number of extant individuals (meaning still alive/active) who has both considerable field experience in a number of different countries combined with familiarity with herbarium specimens (again in a number of different countries). I have a great deal of respect for many plant taxonomists, who over the centuries have performed remarkable tasks, interpreting plant variation from a minimal number of often inadequate, poorly gathered specimens. They have done their best but if the ONLY source of information are dried, pressed specimens, only so much can be achieved. It is high time, greater emphasis is placed upon observations of FRESH/LIVING material, whether directly in the wild (including the invaluable permanent records which good quality close-up digital images now can bring) and examination of live plants grown from known provenance. There is still a need for pressed specimens (and herbaria) but the botanical 'establishment' which primarily consists of senior individuals of my parents' generation, needs to take better advantage of what the digital world offers.

So let me suggest the two species of CONYZA which I have JUST 'recognised' locally.


Crawley calls this the 'Southampton Fleabane' (CONYZA BILBAOANA); he says the pale, yellowish-green flower heads are small 4mm long and 3mm wide, held in terminal groups of 3-5 on long slender inflorescence branches; the outer bracts are about half the length of the involucre; the achenes have sparse, spiky hairs, especially towards the top

Small, hairless, involucres (apparently reminiscent of CONYZA CANADENSIS)

A few seeds with pappus still attached

He found it to be local and still rare in 2004, recently established, but already locally common on dry disturbed ground and stonework in some towns, particularly in East Berkshire

It has the stature of CONYZA SUMATRENSIS

Crawley says it has stout, red-streaked (these are reddish but not streaked), densely long-hispid stems

Crawley describes the stems as being densely long-hispid that are often branched from the base (10 flowering stems is not uncommon) bearing rounded-topped cymes of numerous tiny flower-heads

He describes the leaves as dark (these are not), glossy-green (rather than matt, olive green in CONYZA SUMATRENSIS) but unlike CONYZA CANADENSIS which has straight, spreading hairs on the leaf margins

Upper leaves

Upper surface of upper leaf

Lower surface of upper leaf

Upper surface of lower leaf

Edge of lower leaf; Crawley says that in CONYZA FLORIBUNDA the marginal teeth towards the base of the leaf are enlarged into forward-pointing lobes, 5-8mm long and 2mm wide; towards the base of the leaf the under-surface of the midrib bears long, 8-10-segmented transparent hairs

Lower surface of lower leaf

Prominent hairs on midrib



I recognise this as what Crawley names as the 'Guernsey Fleabane' (CONYZA SUMATRENSIS) on the basis of the involucral bracts being conspicuously hairy, plants olive green, over 1m tall and barrel-shaped capitulate; but I cannot see that the foliage is 'broad-leaved' (perhaps this will make sense when I find my first CONYZA BONARIENSIS)

Two capitulae

Hairy capitulae - the authors of the BSBI reference above say the key features of this species are: the large capitula more than 5mm (whereas on this specimen they are just over 4mm) and tapered; phyllaries very hairy, noticeable without a hand lens plus the central disc florets have 5 lobes (I saw this easily under x 20 with a binocular microscope); they are robust plants with a noticeably dense inflorescence

Specimens growing in my own "un-tended" front garden beside a busy road

My house is just across the road from the Langley Leisure Centre; Crawley (Flora of Berkshire, 2005) found this to be widespread and locally abundant. A dull, olive green plant with hairy involucral bracts. Usually a single stem (not branched from the base), with the flowering branches originating from the top third of the stem (sometimes as low down as half-way) to form a diamond-shaped inflorescence. One of the most recent additions to the naturalised British flora. Naturalised in London since 1983 and locally abundant on urban waste land in the capital since 1990; much less of an arable weed than CONYZA CANADENSIS and more of a plant of open waste ground - interesting that he considers its niche appears to be filled by LACTUCA SERRIOLA in West Berks

I am SURE these weeds are sending my neighbours' nuts - it was bad enough that my garden was full of odd 'Himalayan' plants and not a neat lawn but to allow these giants to run riot..... Serves them right for contributing to my decision to remove my 'Himalayan' garden.

The heads of CONYZA have a few central hermaphrodite florets surrounded by numerous female florets with filiform tubular corollas

Pappus formed on four flower-heads

Few seeds left from head bottom left

Flower buds

Foliage - spirally arranged simple leaves

Hairy stem

Non-flowering shoot

Upper surface of leaf

Lower surface of leaf



'Mexican Fleabane' (ERIGERON KARVINSKIANUS) was not known to Druce a century ago; nowadays it is rare on walls & pavement cracks in Buckinghamshire (Maycock & Woods) - here at the base of a wall in Langley, just metres from the parent plant in a low garden brick wall

Crawley (Flora of Berkshire, 2004) observes that this common rockery and garden wall plant is locally naturalised on brick and stonework but never found far away from houses (as is the case here); often long persistent on old walls and bridge; he found it on ancient brickwork of the canal bridge at Hungerford (which is illustrated below)

Growing on the canal bridge at Hungerford, Berks


Is this LINARIA x DOMINII ? Or just a variant of LINARIA PURPUREA?

Photographed near the motorway just beyond Old Slade Lane, Richings Park, Iver, Buckinghamshire

Could this be a cross between LINARIA PURPUREA and LINARIA REPENS or is it closer to a cultivar of LINARIA PURPUREA?

I came across this in waste ground near to the motorway close to Old Slade Lane, Richings Park

Young green capsule

Note arrangement of leaves - very different to LINARIA PURPUREA

Section of hollow stem

Leaves linear-lanceolate

Foliage of rather 'weedy' specimen resembling that of LINARIA PURPUREA

It is always inspiring to come across a plant one has not (knowingly) seen before and I always relish the challenge of identifying them! I had set out just after 0600hrs on August 15th 2015, primarily to secure photographs of the foliage of 'Chicory' (CICHORIUM INTYBUS) which I had photographed in flower only on a couple of occasions beside a field at the end of Old Slade Lane a few years ago. The important consideration was to reach BEFORE the bright sun came up to making it tough (if not impossible) to get a satisfactory exposure. This widespread plant is also found in Kashmir, so I shall include the images within my A-Z PHOTOGRAPHIC GUIDE OF WEST HIMALAYAN FLORA. The excursion brought back memories of time spend in the early 1980s (after my parents moved to Langley, which I initially used as my base) producing a CHECK-LIST of the FLORA of what was then OLD SLADE LANE nature reserve, run by voluntary warden Bill Watkin-Williams, a Richings Park resident, on behalf of the then Bucks, Berks and Oxfordshire Naturalists Trust - in a vain attempt to protect the place from further gravel extraction. Bill would have been dismayed at what has happened....

Towards the end of my outing, I wandered around waste ground close to the motorway, where I had photographed 'Teasel' en masse, in 2012. What immediately seemed to be a toadflax, caught my eye, consisting of a small colony of a few specimens - presumably an 'escape'? It did not match either 'Common Toadflax' (LINARIA VULGARIS) which I know well, having photographed it in Iver Heath several years ago, when first experimenting with a digital camera (this plant is a native, common in grassy and cultivated fields, hedgebanks and waste places). Nor did it fit 'Purple Toadflax' (LINARIA PURPUREA) - which grows as a weed in my own front garden (this species is introduced, much cultivated in gardens and sometimes naturalised on old walls and in waste places - originating in Central & Southern Italy and Sicily). One, rather straggly specimen, of the toadflax I had found showed similarities to this species foliage-wise; the other examples most definitely did not.

I spent some time checking as best I could, all other toadflaxes recorded for the UK to see if it readily matched any. As its foliage had a 'Mediterranean' feel to it, I paid particular attention to any from more arid regions of the world. I was immediately frustrated that despite having taken a quite a number of good digital images, the two obvious people to send a selection of them to, for their thoughts identification-wise (and potentially a short-cut compared to having to devote a lot of time and effort to the task), do not have e-mail (and it would probably not be a simple matter for them to view the images if I had sent them on a CD).... So much for my wonderful idea of having many more close-up photos for each species to aid identification! This only works if EVERYONE has access to the internet. There are still many people either not with a computer at all or barely utilising them. This includes quite a number of this country's leading field-botanists! I sent a CD of images from Nepal a couple of years ago to a cousin of mine keen on flowers; they were unaware that they could easily use the good quality computer installed by their children to view the images..... Such lack of familiarity with IT is going to be a major obstacle in my advocacy of the use of digital photography for improving plant photography. Many of this country's plant experts, accustomed to ONLY utilising line drawings and pressed specimens, familiar only with the LIMITATIONS of traditional photography, may prove "hard to reach".

None of the LINARIA species with previous records of having been naturalised, fitted well nor any other species which I was able to access worthwhile images/descriptions of on the internet. This prompted me to purchase copies of 'ALIEN PLANTS OF THE BRITISH ISLES' (Clement & Foster, 1994) plus 'ILLUSTRATIONS OF ALIEN PLANTS OF THE BRITISH ISLES' (Clement, Smith & Thurwell, 2005). The latter publication only has line drawings of LINARIA MAROCCANA (which I already knew it was not) and LINARIA DALMATICA (which, strangely enough, I knew well from the Kashmir Valley, as LINARIA GENISTIFOLIA - where it is cultivated and occurs as an escape); this has attractive yellow flowers with orange centres. I wrote out the full list of Linarias in alphabetical order from Clement & Foster, checking them all, leaving the one hybrid to last! Of course it turned out to be closest to this one: Linaria x dominii Druce; I immediately knew who Druce was - none other than George Claridge DRUCE, author of 'Flora of Buckinghamshire'. This persistent alien is mainly found at ports and by railways. It is understood to be a hybrid of LINARIA PURPUREA x LINARIA REPENS; hybrid swarms have been recorded.

I do not know LINARIA REPENS. Druce recorded it as locally common in waysides, dry stone walls, walls, cultivated fields and railway banks, with a distinct preference for calcareous soil, a century ago in Buckinghamshire; nowadays it is rare in Buckinghamshire on grassland on calcareous soils (Maycock & Woods). So IF the plant is a cross between L.PURPUREA and L.REPENS, it is not likely to have been of recent occurrence in Buckinghamshire.



Druce found 'Purple Toadflax' (LINARIA PURPUREA) quite naturalised on walls in a few places in Buckinghamshire a century ago including Denham; glabrous glaucous perennial

Nowadays, common on walls and waste places near habitation in Buckingamshire (Maycock & Woods); stems branched above; flowers numerous (15-40) in dense racemes terminal on the stem and branches

Crawley (Flora of Berkshire, 2005) found this on old walls, railways, pavements and dry waste ground; a frequent garden escape, readily establishing itself if undisturbed; commonest in towns; pink flowered individuals occur occasionally - now frequent and widespread in East berks including by the railway at Maidenhead; in West Berks frequent on dry ground throughout - pale, almost white-flowered plants observed on railway between Tilehurst and Pangbourne

Corolla c. 8mm, violet

Spur long, incurved, more than half as long as corolla

Young capsules (longer than calyx) + seeds

Seeds - angled, wingless, reticulate

Leaves linear to linear-lanceolate


Lower leaves

Upper surface of leaf

Under surface of leaf

Root system



There is no mention of the 'Apple of Peru' (NICANDRA PHYSALOIDES) in Druce's 'Flora of Buckinghamshire, 1926'. Given how distinctive the plant is, it seems unlikely that he would have missed it. There is also no record in his 'Flora of Berkshire, 1897'

Nowadays it is very rare on disturbed ground in Buckinghamshire (Maycock & Woods) - as well as arriving uninvited into my own garden in Langley (I did not plant it), I have seen this growing in other local gardens, so no doubt it has naturalised in a few bare and waste places; an annual, erect, glabrous herb, 30-90cm

Crawley (Flora of Berkshire, 2005) found this to be a rare casual on rubbish tips in East Berks (Including Reading) and also West Berks; flowers blue, 2.5-3.75cm diameter, single on recurved, usually axillary stalks; corolla bell-shaped, limb spreading, 5-lobed

This is member of the SOLANACEAE (Deadly Nightshade Family) is an annual; filaments hairy, bases dilated, covering to ovary; style linear, stigma 5-lobed, lobes cohering

With beautiful, distinctive bright blue flowers; calyx lobed nearly to the base, segments ovate, cordate, acute


A strongly accrescent (becoming larger after flowering) bladdery calyx which is cordate at the base- which encloses the berry; this is young and green - the net-veining becomes more prominent as it ages

Top of calyx

Globose shiny dark berry, 1.25cm diameter, loosely enclosed by the enlarged, membranous, net-veined, 5-angled calyx; ovary 5-celled

Upper surface of leaf - leaves stalked, ovate-lanceolate, 10-20cm, irregularly, sinuately lobed and toothed

Lower surface of leaf

Prominent dark spots on leaves and calyx



Druce (Flora of Buckinghamshire, 1926) makes no mention of this pokeweed; being so distinctive and easily spotted, he is unlikely to have missed it

Maycock & Woods (Checklist of the plants of Buckinghamshire, 2005) also do not mention this; fruit dark purple, succulent, crowded in an erect, thick raceme 10-20cm long

'Flora of the British Isles, 1962' only mentions PHYTOLACCA AMERICANA; carpels separating when ripe, reminiscent of blackberries; each containing a single black, shining, kidney-shaped seed

This plant (specimen above with some carpels removed) is mentioned in 'Alien plants of the British Isles' (Clement & Foster, 1994) - with the authors describing it as part of the PHYTOLACCA ACINOSA group, the 'Asian Pokeweeds', a complex of intergrading species and possible hybrids; established garden escapes in a few places in the south including Ipswich and Kew Green; the excellent NATURESPOT website has an image of this plant, which represents the first record for LEICESTERSHIRE & RUTLAND (BSBI vice-county 55) - which is in the midlands

Crawley (Flora of Berkshire, 2005) which he calls 'Indian Pokeweed' says that Druce did not record it in 'Flora of Berkshire, 1897'; he has scattered records: local and rare in Ascot; occasionally in Reading and West Berks

A nearly glabrous, erect herb; stems 90-150cm, robust, succulent; flowers 0.85cm diameter (some descriptions say pale green in colour, whereas in this form they are white), 2-sexual, in leaf-opposed, cylindrical racemes, 5-15cm long; bracts linear; perianth of 5 nearly separate segments; stamens 8-10, filaments united at the base, anthers 2-celled, soon falling off

Belongs to PHYTOLACCAEAE family - which is separated from CHENOPODIACEAE by the larger number of stamens and compound ovary (not that one would say the families look similar)

Young green fruits; ovary composed of 6-8 carpels arranged in a whorl, each with a short, recurved stigma


Leaves alternate, broadly lanceolate, 15-25cm, entire, narrowed into short stalk (some descriptions say long-pointed but this form is not); stipules none

Lower surface of leaf