This member of the Boraginaceae family is becoming increasingly known, and is now stocked by many nurseries and garden centres. A decade or two ago some of these suppliers were unfamiliar with these plants or perhaps did not regard them as garden worthy. As with most plant genera, there are many species, although only a modest thirty-five in this case, but it is just a few that have brought comfrey to our attention.
In particular the use of comfrey as a fertiliser has long benefited many gardeners. The wild or common form, Symphytum officinale, is a valuable source of potassium whether dug into the ground, used as a mulch, added to the compost heap or, more especially used as a liquid fertiliser if given time to decompose in water; excuse the smell! One of the leading pioneers of organic gardening, Lawrence Hills, was a strong advocate of using Symphytum x uplandicum, a naturally occurring hybrid (S. officinale x S. asperum) discovered in Upland, Sweden. Hills particularly favoured the form entitled 'Bocking 14' since it was proven by the Bocking Research Station to have the highest potash content, and is quite widely available today.
Increasingly though there seems to be an appreciation of some of the other qualities of comfrey. It blooms early and stays in bloom for a couple of months even if the colour of the blooms begins to fade. It is reasonably tolerant of most growing conditions though preferring sun or semi shade and moist soil. Propagation by division is easy. Alternatively it is possible to use root cuttings though personally I have never tried this. Of course the plant has some disadvantages. It can be invasive. The leaves may suffer from rust or powdery mildew in the autumn - a problem which I have not experienced. When moving comfrey beware of leaving roots behind since they are more than likely to regenerate.
Personally I favour S. caucasicum for its quite vivid blue flowers which appear in March and last through to late May though by that time they have faded to powder blue. However the roots tend to run and after a few years vacate their designated planting area. Far more compact in the area it occupies is S. 'Hidcote Blue' with its pretty bicolour blue and white flowers, again long lived. We once had 'Hidcote Pink' which was pretty and slightly less vigorous but was lost when we moved counties.
All in all symphytum in its various forms is well worth trying but do have the spade ready if it becomes too unruly
First published in the Devon Group Newsletter, June / July 2012
and subsequently in Cornucopia Issue 31.
© Copyright for this article: Frank Caunt
This article was taken from a copy of Cornucopia that was published in 2013. You could be reading these articles as they are published to a national audience, by subscribing to Cornucopia.