Garden School:

Garden School:
Teaching this week: Rose pruning (as always!) and water management

Thursday, 6 September 2012

The Hunt for the Hemlock

Hemlock? What, that poisonous stuff?

Yes, that poisonous stuff.

Morag, one of my botany crew, emailed me last week to say that while out botanising, she'd found what she thought was Hemlock - Conium maculatum - and would I have a look to see if I agreed.

I know what you are thinking: "Looks just like Cow Parsley!"

Yes, there is a running joke that most people assume that white-flowered "stuff" on road verges is Cow Parsley, but actually there are a large number of Umbellifers - that is, plants who present their flowers in the typical Cow Parsley stiff flattened bridesmaid's bouquet, think "umbrella" - and it's quite a knack to differentiate between them.

Morag is studying Umbellifers as her specialist subject this year, so she's been on the look-out for interesting ones, and this certainly is an interesting one! It definitely looks like Hemlock -  purple stem and all - but Hemlock is supposed to flower much earlier in the year, June to July.

Having looked at her photos, I tend to agree: the only other possibility is Rough Chervil, which also has a reddish stem, although that also is supposed to flower earlier in the year. So how do we check what it is?

(Brace yourselves for a Botany Bit:)

Right, first things first, that purple stem is a very definite feature, so let's take a closer look at it: clever Morag has worked out how to take photos through her hand-lens (essential equipment for all botanists, preferably worn around the neck on an old shoelace).

Here you go - the hand-lens is like a small portable magnifying glass, but rather stronger than the ones you see used in 1950s detective stories.

Brilliant picture, eh?!

You can clearly see that the stem is green, but mostly covered with purple spots or blotches, which have run together to give the impression of an overall purple stem.

There are only three commonly-found Umbellifers with purple stems, so let's have a look at them:

1) Hemlock - our first suspect.

2) Wild Angelica or Angelica sylvestris (anything whose second name contains "sylv" means "of the wood", by the way, which can help to identify  plants - see, Latin names are not useless!)

3) Rough Chervil (or Chaerophyllum temulum) I know, these names, these names, but it's really important to get to grips with "proper" or scientific plant names.

Why? (warning: digression) Well, take Hemlock. It's poisonous - very poisonous. Apparently eating six or eight leaves is enough to kill you. (Memo to self: should talk with Morag about whether we should destroy this plant before it forms a colony?) But what exactly do we mean when we say Hemlock?

Proper Hemlock: family name Conium - comes in two species, both poisonous.
Water Hemlock: family name Circuta - four species, three of which are poisonous.
Hemlock water dropwort: family name Oenanthe - one species of this family is "grown and relished as a vegetable" in Asia, several other species are poisonous, and one species in particular is poisonous enough that eating one root is sufficient to kill a cow. You really wouldn't want to get them the wrong way round, would you?
And then there is Hemlock the tree: family name Tsuga - absolutely not poisonous at all.

Anyone cropping the "Hemlock" tree and hoping to kill a rich relation would be very disappointed.

But this illustrates the importance of learning the proper names for plants.

So where were we? Oh yes,

Hemlock has smooth hollow stems with purple blotches.
Wild Angelica has hollow purple stems.
Rough Chervil has solid, hairy stems with purple spots.

(There are several additional characteristics that can be checked to confirm the ID, but I won't bore you with them here.)

Morag and I independently checked the stems: hollow, and not hairy. OK, not Rough Chervil then.

Wild Angelica's stems are homogenous purple: we know this because we have found and identified it a couple of times recently. This plant had a blotched stem.

Finally, checking the foliage, this plant had finely cut, fern-like foliage, as per the description of Hemlock, whereas Wild Angelica's leaves are quite different (technically they are pinnate) and, again, we were familiar with Wild Angelica having found it recently.

So, Conium maculataum it is!

And in case you are wondering, I checked with the county wildflower officer, and no, we don't have to report it or destroy it. Although they did suggest that if there was a school nearby, it could be used as an educational resource to teach the kiddies what not to eat.

No, that's not a joke: apparently in days gone by, children were taught about Hemlock, Briony, and all the other horrors of the natural world, but these days they are not. Something about health and safety and outings, or some such rubbish?

Anyway, Hemlock was more or less sprayed out of existence, but recent changes in agricultural policy mean that it is having a bit of a renaissance, and is once again starting to appear growing wild.  The problem is that hollow stem: children used to use them for pea-shooters, which led to numerous cases of poisoning. Hence the importance of teaching children about natural dangers.

But to be honest, I don't think the children of today would think about making pea-shooters, would they? They don't seem to play outdoors without props, as we used to (oh blimey, I'm turning into Sorrowful, Acacia Avenue, writing letters to the paper that start "Why oh why is this allowed to go on?"), they seem to have phones stuck to their ears or their thumbs all the time, not leaving any spare grip for carrying peashooters.

Besides, their idea of a practical joke seems to involve changing someone's  Facebleurk status rather than pinging a pea at them. Ah, how times have changed.

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