EDIT: I am retiring and no longer growing comfrey for sale. The original post has been edited to leave only general information on the use of comfrey.
SUGGESTIONS
FOR USING DRIED COMFREY
N.B. WEAR GLOVES IF HANDLING DRIED LEAVES – I DO.
I had analyses carried
out for two cuts of dried leaves and stems for Nitrogen,
Phosphorus, Potassium and Calcium, combining the samples for a composite result. The analyses of this mixture were Total
Nitrogen (Nitrical and Ammoniacal) 2.2%; Phosphate 0.9%; Potash 6.1% and
Calcium 2.2%. P is low in comparison to the others, but the required level of P
in the soil (measured in parts per million or milligrams per kilogram) is also
low. Additionally the amount of P removed by crops is normally considerably
lower than that of K removed.
The percentages of NPK
and Ca are lower than in conventional fertilisers and it is not intended that
comfrey should be the sole source of nutrients for any crop or plant. Think of
it as a booster feed. As with FYM, I am of the opinion that it does more good
than its analysis suggests. I have no scientific explanation for this view but
I liken it to having a bowl of soup on a cold day – the effect of the soup far
outweighs the nutrients in it.
Suggestions are based on my own
experience which was developed from and supported by information from Growers’
Organisations, government and University agricultural and horticultural
departments, published research, and information from reputable organisations
regarding nutrient uptake of individual plants of various crops.
Houseplants are a good
starting point for suggested use of the dried leaves because they need so
little by way of fertiliser provided they are potted into a decent soil in the
first place. Comfrey can be incorporated into the potting mix. My
recommendation is that 30g is either worked into the top inch
of soil in the pot with something like an old kitchen fork, or alternatively a
shallow trench is made around the pot with the same implement, the dried comfrey spread around this trench and then covered over with the soil
that was removed to make the trench. Continue to water in the usual way and the
nutrients in the comfrey will be released for the plant to use. 30g every two months or so whilst the plant is growing is enough for table top or
windowsill sized plants. It is not necessary to add comfrey if the plant is
dormant in the winter – wait until spring growth commences.
Ornamentals in outdoor
tubs or the ground should be treated in the same way. The user will need to
make a decision as to how much to use, depending upon the size of the plant, but
make the comfrey go a long way. I would suggest that making a trench as described above around any
ornamental and then applying comfrey sparingly, but enough that you can see you
have put some in there, then covering it up again, is both economical and
useful. 4 to 6 weeks’ intervals from the beginning of new growth in the spring
until early autumn should be sufficient. One heavier application in spring is
an alternative method. Stop fertilising before leaf fall or dormancy.
Whilst all plants will
benefit from comfrey applications, high Nitrogen users such as leafy greens in
the vegetable garden need an extra source of this. Comfrey can be applied to
the planting hole if transplanting and also worked in as with ornamentals.
Comfrey really comes
into its own with fruiting and non brassica species – or brassicas such as swedes
that are grown for the root rather than the leaves. I like it for alliums in
particular. The dried comfrey can be worked into the soil once plants have
achieved good growth and are beginning to form the parts used for consumption –
i.e. root swelling in swedes, bulbing in onions, clove formation in garlic, and
increasing stem circumference for leeks. All of them will benefit from
applications of comfrey every few weeks after the growth stages mentioned, and I
would suggest 30g per square metre per month is adequate for those plants
destined for kitchen use. Use of comfrey commences part way through each
plant’s growth so the number of applications is limited. Very short term crops
such as radish and white turnips are used quickly enough that they would only
benefit from comfrey worked into the seed bed. A later application to the soil
is not needed.
Leeks grown for the
show bench, and indeed any other show vegetables, are special cases where the
cost of fertilisers is not normally something the grower is bothered about. In
these cases apply as much comfrey as you are inclined to use along with your
usual special treatment of your plants.
A good method is to put
short lengths of one or more tubes of some sort part way into the ground near
each plant - downspouts, drainage or any large bore plastic pipes are ideal for
this purpose. Put the comfrey into the tube and water the plant through the
tube. This way the nutrients in the comfrey are gradually carried to the root
zone. Add more comfrey as you think fit. This system is especially recommended
for production of big cucurbits such as marrows, pumpkins and squashes. Wait
until the first fruits have set before beginning to use comfrey.
Potatoes and tomatoes are
the two crops that have historically received the most attention from comfrey
users. My suggestion for potatoes is to place the seed tuber (preferably on a
layer of manure) in a shallow trench and spread comfrey around it, about two
inches away from the tuber, and then cover in your preferred manner. I like
manure for potatoes and the comfrey increases available potash levels. I always
make a large ridge at this stage, but others prefer to just cover the tuber and
build the ridge later in the season. If you ridge later then you can apply more
comfrey to the ground and close to the potato haulm immediately prior to
forming the ridge. Comfrey can be worked into the ridge later, but take care
not to break off the growing new potatoes.
Tomatoes can have
comfrey added to the planting hole, and then do not use again until the first
flowers are open. Other people suggest that you should wait until the first
truss is expanding in size. The choice is yours, but I prefer to begin at
flowering and cease a while before harvest is complete – comfrey is not as
quick acting as soluble chemicals. How much to use is a debatable matter. The
makers of commercially available liquid and solid tomato fertilisers advise
feeding very heavily and very frequently. I think that most of them advise
excessive use of their product.
Assuming you have
planted tomatoes into fertile soil, compost or grow bags, I
believe that the tomato plant is capable of producing to its capacity with some
little and regular comfrey applications, say 30g every 3 to 4 weeks, either
worked into the top inch of soil, or through tubes as for leeks. I favour the
tubes. Cease feeding when there are still a few tomatoes left to harvest. There
will be some nutrients left from previous feeds and there is no point in
applying excess that will not be used. Treat sweet peppers in the same way as
tomatoes.
Comfrey could be used
for fruit trees and bushes, but it is not economical for anyone buying it to
use as a prime source of nutrients, and even using it as a booster as for small
plants would become very expensive. I have not done any calculations for
bushes, but it takes all the nutrients from 6kgs of dried comfrey (that is
about 50kgs of fresh leaves) plus extra nitrogen to supply the major elements
removed in a moderate crop of olives or almonds from a single tree that is
lightly pruned – there is loss of nutrients in the prunings. Other fruits would
require similar amounts. This does not allow for the facts that more is
required to keep the tree growing and that the tree does not take up 100% of
available nutrients, although they must be applied to the soil to avoid
shortages. 70% uptake is about as much as can be hoped for, meaning almost 9kgs
of dried comfrey per tree per growing cycle would be required. If the comfrey
is properly fertilised then the trace elements in this amount should be enough.
Comfrey can be fed to
pets and farm animals. It takes about 250g of fresh leaves to produce each 30g
pack. I suggest that the comfrey is mixed into a wet or at least moist feed,
such as a mash, rather than offered dry. Use sparingly. I have seen 20g per day
suggested for horses, but no indication of the size of horse was given, and I
have not used dried comfrey for my own stock, I always feed it fresh.
