Although the past week has been cold and showery, we have had a very sunny and dry spring, with a lot of warm sunshine. Butterflies, bees and hoverflies have loved this weather and we have had many new sightings, on Rose ‘Canary Bird’, dandelions and perennial wallflowers in our back garden and, a short walk away, in Earlham Cemetery.
A star attraction in Earlham Cemetery has been Green Alkanet, Pentaglottis sempervirens. It is a pretty plant on its own, but it becomes more interesting when its flowers are visited by numerous insects.
Green Alkanet is native to south-western Europe and was introduced into British gardens before 1700 and made its first recorded escape into the wild in 1724. It is still increasing its range here, and now occurs in many parts of the British Isles.
In ‘Flora Britannica‘, Richard Mabey describes Green Alkanet as “a pert, bristly, medium-sized perennial”. The plant dies down in late summer but comes into leaf during the winter or very early spring – hence the scientific name sempervirens (“always alive”, or “evergreen”) and the “Green” part of the English name. The word “alkanet” comes from the Arabic word for henna, via Mediaeval Latin, Old Spanish and Middle English. Pentaglottis is from Greek, meaning “five tongues”, which presumably refers to the flower petals.
The leaves of Green Alkanet are fairly similar to Comfrey but are rougher and more bristly with white spots. By April or early May the plant has elongated and produced pink buds which open to beautiful borage-blue flowers with a white eye, which look rather like supersized Forget-me-nots. The resemblance of Green Alkanet to Comfrey, Forget-me-nots and Borage is not co-incidental: these are all members of the Borage family, the Boraginaceae.
It is not surprising that Green Alkanet is doing well. It isn’t fond of acid soils but it will tolerate shade as well as sunshine. Although it often grows in damp places, it is also happy on our local allotment site in sandy loam. It has a deep tap root which is hard to pull up and it is easy to leave pieces behind, which will keep growing. The plant also spreads by seed. Many gardens in the Unthank Road and Earlham Road area of Norwich are full of Green Alkanet and it was a serious weed in the Belvedere Centre garden. The RHS website recommends various strategies to get rid of Green Alkanet but I would urge you to dig up the roots and to stop the plant from seeding, rather than poison your garden with glyphosate. You can put the leaves on the compost heap, but don’t include the roots as they are likely to regrow. Alys Fowler suggests making a weed soup out of it to feed plants. Like comfrey tea, it will smell bad, but act as a great plant food. Wear gloves when handling the leaves, as the coarse hairs can cause a rash, due to structures known as cystoliths made of silicon dioxide and calcium carbonate.
Green Alkanet flowers are edible but rather tasteless and can be used to decorate salads, in the same way as Borage flowers. The plant may have been introduced for a red dye in its roots, although it may have been confused with the similarly named Alkanet, Anchusa officinalis. Clive Stace and Michael Crawley in “Alien Plants” think “it is a bit of a mystery why this species should be grown at all”.
But I think there is a good reason for liking and growing this plant: its wildlife value. If you have space, or in a wild area like Earlham Cemetery, Green Alkanet comes into its own. Its leaves are used by at least two species of leaf-mining flies (Agromyza sp.) and a micro moth (Coleophora pennella). It is also one of the foodplants of the Scarlet Tiger moth.
In Earlham Cemetery, the flowers are attracting Orange Tip and Green-veined White butterflies, hoverflies such as Rhingia campestris and solitary bees such as the Common Mourning Bee, Melecta albifrons and Gooden’s Nomad, Nomada goodeniana.