A succession of white Umbellifers (Apiaceae) can be found on campus through the spring and summer and well into Autumn. The first to flower is that harbinger of spring Anthriscus sylvestris (Cow Parsley) very obvious in April to June in rough grassland, hedgebanks and woodland. This is followed in May-June by Conopodium majus (Pignut – the swollen root tubers ‘pignuts’ are edible and sought out by wild pigs and look and taste rather like hazel nuts), this species is frequent in the grassland under the big oaks in the Harris Garden. Following in June-July is Oenanthe crocata (Hemlock Water Dropwort – don’t seek out the large swollen root tubers of this species, even though they look a bit like potatoes, they are deadly poisonous), this species occurs most conspicuously in the wetter, muddy areas around the campus lakes. Several summer flowering species can also be found from June onwards including Daucus carota (Wild Carrot) in the drier grassland on the slopes beyond the lakes, and Heracleum sphondylium (Hogweed – flowering well into September) is very widespread all through the taller grassland areas. A touch later, from July-ish, Silaum silaus (Pepper Saxifrage) can be found occasionally and only in the damper grassland while Pimpinella saxifraga (Burnet Saxifrage) is more frequent but only in the drier grassland areas.
Picking just one of these for a closer look, Hogweed is the most prominent white Umbellifer on campus at the moment (July). Hogweed plants are relatively tall growing to a couple of metres in height, while its giant cousin, the introduced, invasive and toxic Giant Hogweed (the subject species of a current MSc research project at Reading) can reach a suitably giant-sized 4 metres. Hogweed certainly fits the bill of a mainstream member of the Apiaceae and is easily recognised with its pinnately divided leaves and sheathing petioles, all quite hispid to the touch.
The ripe fruits as in many critical groups of plants are very important for the identification of difficult species. The Apiaceae fruit is typically a dry two-celled schizocarp (a fruit that splits into 1-seeded portions – mericarps) with conspicuous stylopodium (swollen base of the styles). In Hogweed the fruits are suborbicular, strongly dorsally compressed with marginal ridges forming a broad wing and with linear oil glands or vittae.
Finally, there are the flat-topped Apiaceous umbels of white flowers, the outer very unequal and all often crawling with copulating as well as less obviously preoccupied insects – all no doubt contributing to pollination – and all no doubt attracted by what must be, to them, the heavenly odour of that most noble of British institutions – the public lavatory! Have a sniff next time you pass a hogweed plant: hogweed – public toilet – public toilet – hogweed – it really is an uncanny (and rather gross) olfactory match!