Phylum: Magnoliophyta - Class: Equisetopsida - Order: Malpighiales - Family: Hypericaceae
Also known as Common St John's-wort or simply St John's-wort, this upright perennial is easily recognised by the translucent gland spots on its leaves.
Perforate St John's-wort is an erect hairless perennial. Its round stems have two raised lines and pairs of opposite linear or oval unstalked leaves bearing scattered translucent gland dots. The translucent dots on the leaves of the plant look like holes when held up to the light, and it is these resin glands that exude the somewhat unpleasant smell associated with members of the Hypericaceae family.
The yellow five-petalled flowers are 1.8 to 2.2cm across and their petals have black dots mainly around the edges. The narrow sepals, which sometimes also have black gland dots, are much shorter than the petals.
Found throughout Britain, Perforate St John's-wort is native to northern and central Europe and much of Asia, but it has also been introduced to many other temperate regions including North America, where it is an invasive weed.
Look out for this wildflower in all sorts of dryish grassland including roadside verges, hedgerows and woodland edges, particularly in sites of sandy soil.
In Britain and Ireland, the various St John's-wort species are wildflowers of summer. Perforate St John's-wort is no exception and can be seen in flower from late June through to September.
The genus name Hypericum comes from the Greek hyper, meaning above, and eikon, meaning picture; it reflects the fact that these plants were hung above pictures in the belief that this would sefve to ward off evil spirits. The specific epithet perforatum means perforated and refers to the translucent spots on leaves of this plant..
The common name also deserves some explanation. The various St John's-wort flowers are virtually guaranteed to be at their peak around Midsummer's Day (21st June) and they have a long and ancient history associated with various festivals and processions that have taken place (and still do in some European countries) at about this time of the year. The Feast of St. John the Baptist takes place around the same time - 24th June - and from this the plant was given the common name that is still used today and which superseded other names given to the plant in ancient times when it was used in Pagan rituals at mid-summer.
Throughout the UK, Europe and the Near East many St. John's-wort species grow both in the wild and as cultivated plants in gardens. One of the most beautiful of the European species that grows in the wild is Hypericum olympicum which has very large flowers measuring up to 5.5 cm in diameter.
Hypericum calycinum, more commonly known to us as Rose of Sharon, originates in the Near East, and has even larger flowers - around 7 cm in diameter - and this is the species most familiar to us from gardens and parks throughout the UK. It is an agressive shrub which has become widely naturalised in the countryside, and can often be seen on roadside banks and verges, and also along railway lines.