Symphytum is also known as comfrey and is well known to gardeners who are keen on green manures and compost teas. It is also used in homeopathic natural remedies, believed to relieve rheumatic and arthritic conditions. So, this hairy-leaved relative of borage has many more uses than just being an ornamental plant. But if you want simply to use Symphytum in a border or woodland it will reward you with excellent ground cover in shade or sun.
There are 35 species of Symphytum. It is a perennial herb and can have blue, pink, white or yellow flowers that are bell-shaped or tubular. The broad hairy leaves are generally green but there are variegated types, such as S. x uplandicum 'Variegatum' Award of Garden Merit (AGM) which has creamy variegations.
They are vigorous plants, most species spreading quickly, so they are excellent for carpeting shaded borders and woodland. Symphytum officinale in fact becomes invasive as it self-seeds freely and is very deep-rooted - which prompted the founder of the organic Henry Doubleday Research Association, Lawrence D Hills, to develop a sterile strain 'Bocking 14'.
Even a small piece of the turnip-like roots will resprout in the garden or compost heap, so care should be taken to manage the plants properly, especially when dividing. Mature plants can be divided in the spring. The offsets produced can then be replanted 60-90cm apart. Root cuttings can also be taken in late autumn. Seed can be collected and sown in spring or autumn and kept in a cold frame.
Symphytum plants like fertile soil, ideally incorporating manure, because they are hungry feeders. Preferably the soil should be moist, but they can cope in dry soils too. They have deep roots, drawing up the nutrients, which explains why they are a successful green manure. Plant them with their growing point just below the surface. Comfrey should not be harvested in its first season as it needs to become established. Any flowering stems should be removed as these will weaken the plant in its first year.
To make a compost tea from comfrey (Symphytum officinale usually, but S. asperum and S. x uplandicum have similar properties) pack a water butt with leaves and steep in the water until it has digested and cogitated. There will be an unholy smell but this is the price you pay for getting liquid fertiliser, rich in nitrogen, potassium, phosphorous and calcium.
When used as a green manure the leaves should be cut and allowed to wilt, and then incorporated into the soil, or as a mulch in the case of soft fruit. Because of the incredible properties of comfrey you can see why it is afforded a permanent bed in many organic vegetable gardens across the country.
WHAT THE SPECIALISTS SAY
- David Ward, plant production manager, The Beth Chatto Gardens and Nursery, Essex
"You can loosely group them into two lots. The ground cover Symphytum include 'Hidcote Pink' and 'Hidcote Blue', which are quite popular. They are good, tough ground cover, liking a shady area, which is dry or moist.
"There are also the taller forms with nice blue flowers. For example S. caucasicum, which has sky-blue flowers and forms clumps, and S. asperum, which has dark gentian-blue flowers.
"If you want something a bit different grow the green and golden leaved variety 'Goldsmith' or S. ibericum 'All Gold', which has purely yellow foliage that rivals the colour of a daffodil.
"One tip is to shear down vigorous types after they've flowered in June and the beginning of July - it keeps them tidy. People can get a reaction when handling their rough leaves, so I recommend wearing gloves."
- Jennifer Matthews, owner, Moorland Cottage Plants, Pembrokeshire
"Symphytum are tough, weed-suppressing ground cover. They can carpet the ground under shrubs. The tall ones are more imposing and can be used as accent plants in a woodland garden. They look good against lacy plants such as Dicentra or ferns. But you have to watch out with some of the Symphytum species, like ibericum, which can be quite invasive.
"S. ibericum 'Wisley Blue' is nice, being tricolour. It has red buds, and grey and blue flowers. S. uplandicum 'Variegatum' has an attractive, tall but compact form. It has leaves with nice cream margins and mauve flowers. I also recommend the variety that originated here - S. x uplandicum 'Moorland Heather'. It grows to around 1m, has slowly increasing clumps and very dark violet flowers."
- Kevin Marsh, grower, Beeches Nursery, Essex
"The ones we are most often asked for are those that are difficult to propagate, such as Symphytum x uplandicum 'Variegatum'. The gold-leaved 'Lambrook Sunrise' is slow to propagate but we have it in good numbers because it has been produced using micropropagation.
"My favourite is S. caucasicum 'Norwich Sky'. It's about 60cm tall, quite upright, with bright, light blue tubular flowers - it's lovely. One I also really like, that not many people know about, is S. cordatum, which has heart-shaped, shiny lemon-and-lime-coloured leaves."
- Shelley Mosco, managing director, Green Graphite Landscape Design, London
"Symphytum is good ground cover, under a light canopy. I like to use it on its own, under trees, rather than as a foil for other plants. It's great with multi-stemmed birch. It can take over, but in a nice way. And it's easy to increase stock as a result.
"I've used S. 'Hidcote Blue' in woodland gardens, in damp areas. It also grows well on banks. The really nice thing about Symphytum is that it doesn't need fussing with - you can take a mower to it and it will still spring up next season.
"I've also used S. officinale as a green manure and planted Symphytum in school gardens because it attracts bees."
SPECIES AND CULTIVARS
S. asperum has branching stems and drooping clusters of ruby-red buds, which open to display intense gentian-blue flowers. Height 91 cm.
S. azureum has bright blue flowers in early summer. Height 45cm and spread 75cm.
S. caucasicum Award of Garden Merit (AGM) has grey-green pointed leaves and clusters of sky-blue tubular flowers, on arching stems. Height 61cm.
S. cordatum is a neat, clump-forming species with heart-shaped foliage and clusters of pale-yellow bells in spring. Height 20cm.
S. 'Goldsmith' has creamy-yellow bordered green leaves with pale blue flowers in May and June. Height 45cm.
S. grandiflorum forms a mound of dark green leaves and has cream flowers which appear in April. Height 50cm.
S. 'Hidcote Blue' forms excellent ground cover, smothering weeds in its path. It has branching stems that bear red buds, which open to reveal blue and white tubular flowers. Height 45 cm.
S. 'Hidcote Pink' is similar to 'Hidcote Blue' but bears pink and white flowers. Height 45cm.
S. ibericum has burnt-orange buds that open to reveal creamy-yellow bell-shaped flowers in spring. Height 30 cm.
S. ibericum 'All Gold' has large leaves that are yellow when young and gradually mature to green. Branched stems carry lilac tubular flowers in early to mid summer. Height 45 cm.
S. ibericum 'Blaueglocken' forms spreading clumps of heavily veined leaves. It has upright branching stems that bear coral-red buds, which open to reveal narrow tubular flowers of light blue in May-June. Height 38 cm.
S. ibericum 'Wisley Blue' has red buds and then pale cream and blue flowers in April and May. Height 20cm and spread 30cm.
S. 'Lambrook Sunrise' produces mounds of yellow foliage with blue flowers in spring and early summer. Looks particularly attractive under deciduous trees and in other shady places. Height 75cm.
S. officinale is common comfrey, the species most usually grown to provide green manure.
S. 'Rubrum' has dark-green leaves and red flowers from May to July. Cut back spreading shoots to the core of the plant after flowering to prevent it taking over. Height 30cm.
S. tuberosum is a clump-forming species. It produces pale-yellow bells on branched stems in spring and summer. Height 45cm.
S. x uplandicum is Russian comfrey, with large leaves and blue flowers. One of the favourites for making green manure.
S. x uplandicum 'Axminster Gold' has golden variegated foliage. Its flowers are on tall stems, but look insignificant, so it is recommended they are cut down to show off the leaves.
S. x uplandicum 'Bocking 14' is the sterile form of Russian comfrey bred for organic gardeners. Stock can be increased from root cuttings.
S. x uplandicum 'Moorland Heather' was a chance seedling found at Moorland Cottage Plants in South Wales. It has striking dark violet flowers from April through to June.
S. x uplandicum 'Variegatum' AGM has green and white variegated leaves and purply-pink flowers in the summer. An erect, clump-forming type. Height 90cm.