Comfrey

In English, the word comfrey is used as the general name for Symphytum species. The same term has been in use in various languages since at least the 1^st Century. Pliny, a Roman, called it conferva. This later became cumfria, then (Old French) confrie, and, with a few alternatives in between, eventually the English spelling of today. Symphytum is derived from Dioscorides, who was contemporary with Pliny, and a Greek physician. His word for comfrey has been variously reported as Syumphuo, Sumphutum, Sumphuton and no doubt other similar words. Symphytum officinale or Common Comfrey (so called because it was the common species in Britain) with white or cream to yellowish flowers also has a red to purple flowered variety S.officinale var. patens. It is totally erroneous to refer to S.officinale as “True” comfrey as some Internet sites do, since about 40 species of Symphytum have been identified. They are native to most of Europe and Western Asia and all are called comfrey in English, the norm being to use a descriptive term or place-name before the word Comfrey, e.g. Prickly Comfrey or Palestine Comfrey. Symphytums cover the range of colours from white through to yellow, and blue through purple to red. The Common Comfrey was introduced to North America at least as early as the 17^th Century, Josselyn (1672) calling it comferie. Some of the other comfreys followed at later dates and some have also been taken to other parts of the “New World” and Eastern Asia.

Some current day herbalists believe that S.officinale is the preferred, or even only, species for safe medicinal use, Officinale meaning “of the (herbalist’s) shop”. They may well be correct, but historically more species have been used. S.officinale is uncommon, or absent (and other species are common) in some areas where comfrey has traditionally been used medicinally. With 18 of the species in Turkey alone, it is not surprising that Dioscorides was familiar with, and apparently used, more than one species since presumably nearby countries have at least several of the species found in Turkey. Gerard in his Herball gives an unusual use for the root juice in ale; it is “given to drinke against the paine in the back gotten by wrestling, or overuse of women”. 

Of most interest to those people wishing to use comfrey for plant food and livestock feeding are hybrids, specifically of the species Symphytum x uplandicum, a cross between S.officinale and another Symphytum and now widely known as Russian Comfrey. S. x  uplandicum is a naturally occurring hybrid, the original being found in Uppland, Sweden and not Russia. Later discovered hybrids were from Russia.  These hybrids rarely set seed, but will provide the pollen to cross with S.officinale and give yet another variation. Borage, Borago officinalis can also provide pollen to produce a hybrid. Both Borage and Comfrey are in the family Boraginaceae. When an unsorted mixture of varieties of S. x uplandicum was sent to North America from Britain in the 1950s there was a “Cold War” between the USA and Russia, so it was given the name Quaker Comfrey. Lawrence Hills was instrumental in exporting this mixture and he was the founder of the Henry Doubleday Research Association. The HDRA was named in honour of Mr Doubleday, who was a Quaker, and he had probably the first ever Russian hybrids in Britain, sent to him by the Head Gardener at the Palace of St.Petersburg.

The most common cultivar in use amongst gardeners and livestock people is S. x uplandicum ‘Bocking 14’ but some, such as myself, use ‘Bocking 4’. Together with all the other Bocking cultivars, at least 21, these were first identified by Lawrence Hills from amongst a large assortment of collections from various people and places. He called each collection a strain or mixture after the people or places where they originated. He did not breed or “develop” the cultivars as is often reported, they already existed, but nobody before Lawrence Hills had identified them as separate cultivars of the same species. In this context please note that a lot of current Internet sites replicate other sites in their supposed “information”. Lawrence Hills warned against such incorrect repetitiveness long before the Internet was invented.  He made great efforts to identify some of the highest yielders, but time and space prevented him doing long-term trials of every hopeful, so if you have a mixture there could be a world-beater amongst them.

All comfreys only actively grow from spring to autumn in temperate climates, dying down before mid-winter, and timing depending upon how “temperate” the climate is. In tropical climates they will grow year round if there is not a long dry season and in temperate areas with a long dry summer they need irrigation for high production. S.officinale sets seed that germinates very easily. So do some of the other Symphytums. Stick to the Russian hybrids if you want to control the size of your plot. Anyone buying named cuttings of a Russian comfrey hybrid, whether root or crown cuttings, also called crown sets or offsets, should find that all plants are of the same cultivar. That means the flowers will all open with exactly the same colour, and fade to the same colour, although there could be some slight variation during the phase from fully open to faded.  If the flowers are not all the same then you have a mixture, and will need to do your own work on identifying the high yielders, just as Lawrence Hills had to do.

Knowing the wide variations that Lawrence Hills found in his mixtures I collected samples of as many collections as I could find when I farmed in the North of Scotland prior to moving to Portugal, with a view to trying to find something that might outyield the Nos. 4 and 14 I already had, along with some S.officinale. I failed to find one in the collections I acquired. I did not have many years to experiment, up to about 7, but with only around 100 plants it was not difficult to spot low yielders and anything that looked promising. Nothing I had acquired was near the 4s and 14s for yield.

I operated a commercial free range egg enterprise on this farm, using mobile night shelters holding either 80 or 120 hens and the hens had free access to all the comfrey beds. They were not interested in the plants at all. This is not unusual, and if you want to offer comfrey to poultry it is best to cut and wilt it first, possibly even chaffing it. I understand this is particularly important for No.14. Poultry apparently find the higher potassium content of this cultivar distasteful when it is growing or offered freshly cut. On the other hand I have heard of people being able to feed it fresh, so it is worth a try if you want to feed it to poultry. I did not attempt wilting and chaffing because I was not interested in feeding it. I had a specially formulated layers’ ration made up for me and delivered in bulk pelletted form. The hens did pick up various tidbits every day, including some greenstuff, but being on a commercial basis, I had regulations to meet as well as endeavouring to sell particularly high quality eggs, and wanted the hens to concentrate on eating the ration I provided. Too much greenfeed can colour the albumen and give an “off” taste.

I kept meat rabbits until the increasing egg enterprise meant I had to cut back on the workload and the rabbits had almost all taken readily to most comfrey leaves they were offered. Some did not like it fresh, wilted or dry. Those that did saved me the cost of bought in hay.

I brought a couple of crown-sets of No.4 with me to Portugal because, following the advice of Lawrence Hills, this is better suited to livestock and I intended to use it primarily for this purpose, the 14 with its higher potash being preferred for plant food, although both can be used for stock; as well as in compost, as a mulch, liquid fertiliser, dug into the ground or laid in drills underneath potatoes. As it happens my land is naturally high in potash so the lower level in the No.4 is not a problem, and the amount is still substantial in any event. One of the analyses made by the HDRA showed No.4 to have 2.35% Calcium; 1.25% Phosphoric Acid (about 0.9% of the P in the N:P:K figures shown on fertiliser sacks) and 5.04% Potash. An analysis of No.14 on another occasion showed 7.09% Potash and lower Phosphorus, with an analysis of No.15 showing similar results to the No.14. Mineral content of the leaves will alter over the course of a season, and I may have my own samples analysed.

I increased the plants from crown sets but only to about 30 plants. I keep a small goat herd of up to 20 does, and they have never been particularly fond of comfrey, often pulling the leaves out of the feeders to try, and then discarding them. I tried many times each summer with only a few does and kids being interested – until this year which began with a particularly dry winter and the usual dry summer, therefore no fresh grazing and very little browse.

Most of the goats took to the comfrey by about the end of July, and my limited stocks had to be fed very sparingly. I have increased the number of plants I have and earmarked another area for a further increase in the spring in the hope that the goats will continue to readily eat comfrey. I hope they do because it makes an ideal complement to maize and beans with a reverse Ca:P ratio to them. Comfrey is higher in calcium. It is also high in protein so can at times replace the beans. I feed some grain and pulses or concentrate all year round, but more in spring and late summer when the comfrey is available and there is limited grazing, either because the fields are shut up for hay in the spring, or because of the dry Iberian summers when pastures do not grow. These two times also coincide with peak lactation of the does and the flushing period (see the Amazing Maize blog). If the goats decide not to eat the comfrey then I shall use it as a mulch around fruit trees.

Whether or not the goats do eat the comfrey I intend to trial it in the Ribeiro Grove of 180 olive trees which I finished planting earlier this year. It will be labour intensive but I believe will be worth the effort. At 6 metres spacing of the trees a comfrey plant can be placed 2m each side of the trees to give two plants per tree. The olive trees have a fairly small root area for a number of years, and not a particularly large one when mature so the comfrey and olive roots will not be competing for space in the soil. The nutrients which the comfrey removes from deep in the ground is kept in the same area under this system, so whilst the soil is being mined, concentrated minerals are returned no more than 2m away and the land does not lose them. Instead they are recycled. Harvesting the leaves and using them for any purpose elsewhere means that the comfrey land loses nutrients.

Obviously some of the nutrients will be locked up in the trees, and the olive harvest will remove some, as does any cropping between the rows, such as the maize this summer, and a current crop of beans. These nutrients need to be replaced, and since I will be fertilising for the crops, they will be. The comfrey and trees will automatically receive their share of the crops’ fertiliser since I use a broadcaster across the whole grove. The area is irrigated via overhead sprinklers and my other grove, the Estrada Grove of 299 trees planted in 2006, is irrigated through drippers, which means that the irrigation is only along the tree lines, but consequently also suitable to take comfrey plants. That is a possibility for the future, but this area is only fenced to grazing livestock standards, and wild pigs occasionally make a foray. I am sure they would destroy a comfrey crop the same as they do a maize crop, so the boundary would need to be pig proofed first.

Another means of using the comfrey would be for me to make liquid manure, simply allowing the comfrey to liquefy inside a container and draw-off the concentrated liquid fertiliser. This could then be fed through the irrigation systems. I have some filters on the lines, but anyone planning on doing this might find that additional fine filters are needed for drip irrigation systems otherwise the drippers can become blocked. The overhead sprayers would not be a problem since they would not block with small pieces of vegetation. If I do use this system, then I will have the concentrated liquid analysed.

A further alternative use that I am also considering is the use of comfrey as part of the feedstock for a small-scale biogas plant. Due to its low C:N ratio, around 10:1, it would make a good feedstock alongside vegetable waste, or a higher carbon crop grown specifically to feed it - especially the forage part of maize. The digestate from this process can be used as a replacement for compost, saving some fertiliser costs, or further used to produce ethanol. I have done a little research and whilst a household sized methane digester is cheap, and feasible on a DIY basis, I have not gone into costs of a slightly larger scale plant, and done very little work on the ethanol production stage because obviously I could not do this without first producing the digestate. My personal use of methane would be to power a generator to pump irrigation water. This means I would only need to produce methane during summer, which fortunately for me is the time when ambient temperatures are ideal for methane production. Consequently I would be using a batch process rather than an all year round constant flow digester. Batch production is cheaper and the equipment less complex although less efficient. This idea too is for some unknown date in the future, and I would work in collaboration with Patrick (see the old blog entitled A Glossary followed by a blog on Olives) since he is much more knowledgeable than me on the technical aspects.