What is an Umbellifer? - and how to tell two of the commonest ones apart

I visited our local RSPB reserve, Saltholme, this afternoon and as well as all the birds - hundreds of nesting Black-headed Gulls and Common Terns, Grey Herons, Little Egrets, ducks of several species, a hovering Kestrel,  Lapwings, a beautiful delicate Avocet with its fine upturned beak, 3 Black-tailed Godwits and a Spoonbill - I saw several large stands of two of our commonest umbellifers.

"What's an umbellifer?" I hear you cry.

Well, I'm glad you asked that. An umbellifer is a member of the plant family Apiaceae. This family includes several plants with which you might be familiar, such as Carrots and Parsnips (it's often called the Carrot Family), edible herbs and spices like Parsley and Coriander, some of our most poisonous plants such as the Water-dropworts, the alien-looking Giant Hogweed (whose sap can give you an nasty chemical burn if it gets on your skin and then the sun shines on it), and that familiar (and not always welcome) prickly seaside plant, Sea Holly.

An umbel

The old name for the family was Umbelliferae and this comes from the little umbrellas that the flowers (and subsequently the fruits) are borne in. Each flower (they are mostly white but can be yellow, blue or even tinged with pink) is borne on a short stalk coming from a central point, like the ribs of an umbrella. The exact number of flowers to each 'umbel' (the name given to the little umbrellas) varies depending on the species and also from umbel to umbel within one plant. Many species carry several umbels together in a large head  - Giant Hogweed is an extreme version of this, with flower heads getting to 80cm (31inches) in diameter.

The two species that I saw today are much smaller than this giant, but can still be substantial plants. The first one I noticed was not even in flower yet, and what I saw first were the feathery leaves and pale green stems blotched with purple that told me straight away that this was Hemlock (Conium maculatum). This is the plant that killed Socrates and apparently various other statesmen and politicians of ancient Greece (it contains an alkaloid that can cause a potentially fatal neuromuscular blockage when it affects the respiratory system). Hemlock can grow to a couple of meters in height but you could be forgiven for mistaking its leaves for those of a fern (which is actually a very different, and much more primitive, kind of plant).

A Hemlock plant showing the flower heads
about to open - they will be umbels of small
white flowers in a few days

Hemlock is one of the few British umbellifers
to have purple spots on its stem, and none of the others are this tall

As I walked away from the place where the Hemlock was growing I thought at first that I saw some more Hemlock, but this time in full flower. Then I looked more closely at the stems and realised that they were a different shade of green, with no purple spots, and also ridged and hairy, and the leaves weren't quite so finely divided. This was a different plant. This was Cow Parsley (Anthriscus sylvestris) - a common plant of roadsides and hedgerows. You will have seen this plant on many occasions, even if you didn't realise what it was. One of the old names for it was Queen Anne's Lace, although Wikipedia tells me that this name is used for several white-flowered umbellifers as well, principally Wild Carrot (Daucus carrot), and I think it is still used for this species in North America.

Cow Parsley

Not all plants that have umbrella-like heads of whitish flowers are true umbellifers. Two common plants that people often mistake for members of the Carrot family are Yarrow (Achillea millefolium), which is actually in the Daisy family, and Elder (Sambucus nigra), of Elder-flower cordial and Elderberry wine fame (not to mention the Elder Wand of the Harry Potter books), which is in the Adoxaceae - the Moschatel Family.