Monday, May 12, 2014

English countryside is being invaded by rampant cow parsley! Parts of the USA too.

He's only just started

And the man with the high-vis jacket has his work cut out for him...(Note the clump of Photinia too btw, the subject of my last but one posting).

Never mind the Day of the Triffids. What about the Spring of the Cow Parsley? Where are the cows, for heaven’s sake? There used to be two or three long-horns in the field near my home.

 That same field is now a sea of cow parsley (above), except interestingly for certain parts (about which more later). Somehow I don’t think it’s the absence of a few grazing cattle that had made the difference. Cow parsley is rampant this year, more so than I can ever recall in the past.

First, an aside re botanical nomenclature. The cow parsley, aka wild chervil,  referred to here to here is Anthriscus sylvestris. Beware. It’s also referred to occasionally as “Queen Anne’s lace” (QAL) and thus a potential  source of confusion, since QAL is an alternative name, especially in the US for ‘wild carrot’, which though having a similar appearance to our cow parsley is a different species (Daucus carota).

Wild carrot (Daucus carota), not to be confused with cow parsley, aka wild chervil.

Now I’ve sometimes pondered in the past on the question why it is certain wild plants have gained the upper hand when there are scores of contenders at any particular time, and cow parsley has been one of them. 

What gives it the edge over competitors? This year there’s so much of the stuff, dominating patches of woodland, roadside verges, even that meadow near me (the site of an abandoned medieval village btw -due to the Black Death) that is usually just grass and buttercups, with or without cattle, that I’ve resolved to settle this question once and for all. Yes, now is the time for a long-postponed act of botanical catharsis, and you dear reader, if still with me, are now the guinea pig for my musings, not to be confused with pedestrian ramblings (mercifully ambiguous). 

 Yes, you dear reader will now be privy (an appropriate receptacle some might say) to my innermost thoughts on nature’s attempts to recolonise this corner of suburbia with a common-or-garden species. (Correction: common only, assuming  that word refers to open non-privately-owned land(?)given the gardeners in this part of the world would never permit cow parsley to intrude on their immaculate borders).

Here's a link to a blog I've just discovered that issues a salutary warning to anyone rash enough to think cow parsley can be allowed in a "back-to-nature-corner" cum wildlife refuge in their cultivated garden.

So here. In chronological order, was my train of thought these last few days, or as some might say, train crash.

I first noticed the invasion of cow parsley where expected – at the entrance and sides of public footpaths. 

I then noticed that a protected area of woodland, like so many others in this neck of the, er, woods,  was entirely taken over. 

Quick look on internet: cow parsley tends to be found in areas of light shade. OK, that fits. But not too shaded. It tends to be at interface between trees and open areas i.e. partial shade, or maybe some kind of transition zone.

 Go back a few yards into denser shade and the cow parsley looks sickly and abruptly ceases.

So I then got to musing about whether it was really the shade it likes, or is it proximity to trees? Could that be possible? Maybe. Despite less light, might there be a thermal compensation? You see, there’s a well known effect in winter, when there’s snow on the ground, even under bare trees: the snow melts faster under the tree, directly over the root spread. It's an effect that has been attributed to the heat released into the soil by actively respiring roots. Metabolism produces heat.

But another observation, and another line of enquiry, suggested itself. Cow parsley is mainly stalk and flowers (albeit tiny ones arranged in those flat umbrels). There’s precious little foliage on them, apart from some small fern-like fronds. 

Where is the plant getting its energy to thrust up so early and form flowers, stealing a march on competing species that seem more preoccupied with acquiring light-intercepting, neighbour-smothering foliage?  More reading on the internet turned up the key word: rhizomes. Cow parsley has underground rhizomes.

Now, if you dig up cow parsley, as I did yesterday with some difficulty (bending my good trowel in the process) there is what I would have called tap roots.

They are not my idea of “rhizomes”, which I tend to think off like the horizontal ones on irises etc.But the darker "root" has those encircling ribs, so it's not a typical root.

A rhizome is in fact not a root, but a specialized underground stem, one that is adapted to storing food like sugars and starch. But who am I to argue, especially as a quick scout around found several references to cow parsley rhizomes, including an authoritative-looking paper describing the extraction of putative anti-cancer agents (more on that later). So it’s a rhizome, says he, trying to contain his initial  misgivings.

But how can a plant have a store of sugar and starch in early spring one may ask, when it has scarcely any photosynthetic capacity, given the nominal foliage? A penny clunked at the back of my mind, and sure enough the next crucial keyword, the one that explains cow parsley’s ability to get ahead in life, appeared in my internet perusal: biennial. Yes, cow parsley is a biennial, with a two-year life cycle. In year 1 it’s (apparently) a squat plant that is easy to overlook, making a rosette of leaves close to the ground.

The squat, inconspicuous habit of cow parsley in Year 1 of its biennial life cycle,

  But it’s busy squirrelling away (if plants can be said to squirrel)  the sugars and starches into that, er, rhizome, while making big ambitious plans for the following year.

Given that biennial lifestyle, there might be two obvious  reasons why cow parsley should be so rampant this spring, bringing out council workers with their strimmers.  The obvious one that springs to mind is the alleged “warm, wet “ winter we have just had. (I personally had only noticed the wetness, and there’s nothing on my latest fuel bill to suggest its was warm). Yes, it’s been amazingly wet, so much so that part of that field in the first picture acquired standing water for several weeks on end,with squelch turf making one’s usual walk something of a test of the water-proofness or otherwise  of footwear.

But there’s another possibility – maybe it was LAST year’s weather, specifically the growing season,  that was exceptional, allowing biennials like cow parsley to build up super stores in those rhizomes. Actually, those rhizomes look a bit skinny to me, dare one say anorexic, hardly likely to take First Prize in the Bumper Rhizome award at the annual flower show. Caveat: I may have done the uprooting too late, after the plant had raided its savings account.
Random thought. You don't suppose, do you, that cow parsley plants arelike those possibly apocryphal  girls in boarding schools who allegedly synchronize their, er, biorhythms?  Or would that be turning an urban myth into a rural, or suburban one?  Surely not. If cow parsley plants were all in Year 1 in 2013, and all in year 2 currently, we’d surely have noticed by now. And insect species that rely on cow parsley flowers for nectar and or pollen would surely have a rough time, having to seek out alternative foods in alternate years. Do I really need to go hunting for early stage Year 1 rosettes among the stalky flowered specimens, to be certain there’s a new generation on the way to ensure next year’s parsley show?  Nope. A hefty dollop of commonsense says I don’t.

Now, about that preferred habitat. It’s clear from my picture gallery that while cow parsley tends to be found close to trees (and hedgerows) and is presumably its preferred location, there’s probably no need to go seeking highly involved reasons for that (like that thermal effect, or even more abstrusely, some kind of love triangle involving the pre-existing relationship that tree roots have with fungi etc (mycorrhizae). That’s because they are well out in the middle of my local meadow, well separated from trees, at least this year (though I don’t recall seeing them there before in the 4 years we have been where we are).

However, they don’t like the trampled bit where we pedestrians tend to cross the meadow. Maybe that’s ground compaction they or their seeds don’t like, or maybe the year 1 rosettes would get trampled were the seeds to germinate.

Cow parsley would seem to prefer shady locations, bordering woodland, but maybe because they are relatively undisturbed, rather than an intolerance for direct light.

So what are the pros and cons of cow parsley? Visually, they add variety and are a harbinger of Spring, although we have plenty of those already in the gardens hereabouts. Personally I consider them over-dominant, and am not too keen on their dubious scent either, politely described on the BBC's gardening site as "malty".  Maybe. An hour or two after imbibing the amber nectar.  NISM?

Grazing animals? 

 Do cows eat cow parsley?

Come on. Make up your mind. Are you going to eat it or not?
 Do they seek it out? How did cow parsley gets its name? Is calling it cow parsley simply a way of saying it's not to br considerd as a gourmet item in the human diet?

There seems to be uncertainty on the internet as to whether or not it’s safe to allow one’s horses etc to nibble the stuff, though several say their pet seems to seek it out with no ill effects. 

That’s assuming those horses are smart enough to distinguish between cow parsley and some almost identical looking leaves and umbelliferous flowers of plants that ARE toxic to people and animals. That’s especially the case with hemlock  (wot did for Socrates).

One needs a keen eye to tell the difference between deadly hemlock (top) and cow parsley (bottom)
Then there’s the giant hogweed

It can create painful chemical burns to exposed skinof both people and livestock  through a devious and highly antisocial defence strategy, one that involves producing chemicals that provoke an allergic photosensitivity. I guess if you are a plant with no flight mechanism, you are left with just the fight option, and a chemical armoury makes up for the lack of tooth and claw.

I see the pharmaceutical industry continues to eye up the plant kingdom in its ceaseless search for novel cytotoxic agents- one that can find uses in cancer chemotherapy. Here’s a link to a paper in which a particularly promising agent  we are told has been extracted from none other than the rhizomes of Anthriscus sylvestris aka cow parsley. It rejoices under the name of deoxypodophyllotoxin, and remarkably (given it's a secondary metabolite) accounts for no less than 0.39% of the plant matter (dry weigh basis) which seems quite a lot.

Obviously, one need to distinguish between the underground rhizomes and the above-ground foliage if discussing toxicity, needless to say. One may be toxic, the other relatively harmless.
If the extracted rhizome chemical and its derivatives prove successful, can we in Britain  look forward to an exploitation of our vast reserves of cow parsley, assuming more warm wet winters?

The get-up-and-go South Koreans are  also busy extracting those promising chemicals from cow parsley.

Might some of  Korea's less successful neighbours beat a path to our door and that of other nations blessed with a surfeit of cow parsley? Might a variant on what you see next become a common sight on British highways and byways (imagine cow  parsley, roots especially,  where you see hay or straw)?  Will we be seeing  eco-friendly draught animals transporting the harvest to processing plants (each animal hopefully being rewarded at its destination with a nose-bag full).

Further reading: Wild chervil - a relatively new weed problem in central Vermont

(Reminder: wild chervil is an alternative name for cow parsley)

Update: have just tweaked the title and search labels, adding a mention of the USA. The transatlantic dimension is interesting, and increasingly a matter of some concern it would seem. Here's an interesting twist to the story, gleaned from another site, quoted verbatim:

Wild chervil (Anthriscus sylvestris)
                             probably arrived in North America as a
               component of British wildflower seed
                             mixes which were used to recreate the
                   floral meadows of Britain. Wild chervil
                       may still be found in some wildflower
                       seed packets and buyers should make
                  sure they have a complete list of the
                       plants they are purchasing. 

Personal observation: it's probably hard to get the general public concerned about a "weed" that gives a not unpleasing frothy look to the countryside each Spring (hard-nosed farmers are a different matter). But think about those entrenched rhizomes, and the steady take-over of any land that is not annually ploughed, crowding out other species, reducing biodiversity, animal as well as plant, altering food chains with their predator-prey relationships, upsetting the 'balance of nature'?

Might cow parsely/wild chervil spread beyond Vermont in years to come. Might it find soil conditions more to its liking further inland, where's there's less competition from competitor species and/or abundant fertilized prairie. Might a satellite map of the USA in 2020 maybe look a bit like this, in the month of May or June?

Update:Monday 19th May

See Michael McCarthy in the Independent: "Cow parsley: the countryside killer".

Update: Tuesday 2nd June 2015

It's now a year later, and there's been quite a few visitors these last few weeks to this posting, prompted presumably by yet another annual invasion of cow parsley. The field with the church tower in the background (see above) is again full of the stuff, so there must be plenty of odd  as well as even year flowerers in the biennial mix, if you see what I mean. I was watching the cows (and bull) in that same field this afternoon. Despite its name, one gets the impression that cows studiously avoid cow parsley, preferring new grass instead.

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