Herbal, Plant and Seaweed Teas & Liquid Feeds

Soaking plants to make liquid feeds at the Stokes Wood Composting Demonstration site

These provide a natural  source of plant nutrients and an alternative to chemical fertilisers and pesticides  which may  harm insects, wildlife, plants and the soil.

 Fermented, or plant, teas are typically produced by soaking un-decomposed plant leaves and shoots in un-chlorinated  water for two or three weeks. During the fermentation period dissolved oxygen will  reach low levels encouraging microbial anaerobic growth but not for the full two to three-week soaking period and  some aerobic organisms will return to activity as oxygen returns

 The fertiliser is best diluted  using unchlorinated water such as rain water.  Generally, the fertiliser should be diluted so that it looks like weak tea normally 10 parts water to 1-part tea. (Also see Compost Teas).  

You can also dilute the liquid and use it as a plant feed, but it is difficult to know exactly how strong it is. A mix of 5 parts fresh water : 1 part weed water will act as a general feed for container grown plants. 

Plant teas which can be applied by watering or spraying are a good source of nutrients. It can be used as an unfiltered as a drench applied directly to the soil or filtered as a foliar spray. An  old pair of tights, cheesecloth or  burlap.  even an old shirt).

  • Nitrogen (N) stimulates leaf growth,
  • Potassium (K) or Potash promotes developing flowers and fruit and
  • Phosphorus (P) enhances root growth.

Water can also be used to kill perennial weeds, including their roots, by drowning. The whole plant is put in al idded  bucket or bin, covered with water.  Weighed  down with a stone or slab to keep them completelysubmerged  The plants are left to soak for several weeks, months or in the case of couch grass a year or longer (some source recommend two years).Either add the resultant sludge and liquid to the compost heap or drain off the liquid and use it aa feed adding  the sludge to compost heap.

Comfrey Tea

Comfrey grows wild on many allotment sites as is a fast growing (and spreading) perennial which will if  given half a chance take over the whole site. For this reason I would recommend buying root cuttings of the Bocking 14 variety. Do not take root cuttings from other plants unless you know it is B14 or it has been grown in situ for a number of years and has not made a take over bid for the site.

Comfrey Tea

Comfrey is the most popular of these teas and we would recommend all composters to make it to supplement their composting and compost teas. 

Comfrey is a good source of potassium and nitrogen. Comfrey tea promotes the development of flowers and fruit and is best applied once the first flowers have set. It is recommended for use on tomatoes and peppers.

The most common method of making comfrey tea  involves soaking the leaves in water but this is the method that produces the famous stinking liquid feed. A barrel or tub is quarter filled with comfrey leaves  topped up with water and allowed to stand for 3 to 5 weeks. To make a good concentrated fertilizer the leaves should be pressed down into the container by a weight of top such as a brick of broken paving slab. Use a conatiner with a lid to contain the smell.

Either use a container with a tap or a hole in the bottom, so that the fertiliser drips into a catch-pot or remove the liquid from above with a watering can. An old Bokashi bin makes an excellent  container in which to ferment comfrey tea as the  filter tray prevents the leaves from blocking the drain tap and the airtight lid contains the smell. 

There are two approaches to maintaining a supply  of feed throughout the summer. Either keep replacing the water as it is used and top up the supply of comfrey ever two or three months. Or once the liquid is used add the sludge to the compost bin, to help keep it moist and as an activator, and start again using the fresh growth that has replaced that which you cut.

 Be warned comfrey liquid produced in this way smells very unpleasant. Use the tea diluted, one-part tea to three parts water, for established plants, either watering into soil or as a foliar spray.   For younger tender plants, such as tomatoes dilute one-part tea to ten parts water and only water into the surrounding soil or you may scorch the plants. 


Concentrated Comfrey Tea

Concentrated comfrey tea

Concentrated Comfrey tea has the advantage of not smelling anywhere near as much as the dilutes version. I recommend that it is made using a drainage pipe fitted with an end cap through which a single drainage hole has been drilled. Comfrey leaves are compressed in the pipe using a plastic bottle filled with sand or water or a sparkling wine bottle which is heavier and more fun to empty before use in the tube.

Larger quantities of concentrated comfrey tea can  be made by packing comfrey leaves into a barrel or a similar container with a tap, preferably compressing the comfrey down with a spade to get the maximum amount into the barrel and then compressing it during fermentation  with a weighted lid. Only add a small volume of water or urine and water to get the flow going. This method is recommended by Nicky Scott in How to Make and Use Compost (Green Books 2009)

Dandelion Tea Liquid Fertilizer

Dandelions can be eaten  in the early spring, the green buds can be eaten, and the opened blossoms used for jelly and the larger leaves dried to make a drink but to most of us they are a weed. But they are a weed that can be turned into a liquid plant feed with the remaining sludge being compostable.

Dandelion Tea Liquid feed

  • Free soaking

Using a 5-gallon bucket with a lid bucket. Dig up the weeds, ( and roots) and put them in a 5-gallon bucket with a lid and cover  with water . Leave  soaking for  2-4 weeks. Stirring when possible but at least once a week. It will smell, hence the lid. After the 2-4 weeks, strain the mix through a cheesecloth  or an old pair of tights. The  liquid  should be applied as a soil fertiliser and the solids/sludge added to the compost bin.

  • Soaking in a  bag

As with other compost and plant teas  it is possible to avoid the need to filter the final solution  by putting the weeds in  a permeable sack before soaking.  Follow the 2- to 4-week waiting period.


Dilute 1 part weed tea to 10 parts water for use on the soil, round plants or as a foliar spray. Do not spray vegetables that are soon to be harvested.



Grass Clippings Liquid Feed

Grass clippings  are readily available in most gardens,  but they are frequently binned to be composted by the council even though they can be home composted (with the addition of adequate Browns), composted with cardboard e.g. grass-boarded,  left on the lawn to be absorbed, used as a mulch or soaked to make a liquid fertilizer with a high potash content.

The conventional lidded bucket soaking method already described can be used.  A ratio of 10 to 1 water to grass clippings by weight is used recommended  but a satisfactory mix has been obtained by using a less accurate visual assessment where the bucket is  2/3 filled with fresh grass clippings  and then filled with water. I would suggest putting the grass in a Compost Sock or old pair of tights before adding the water so that the liquid can be wrung out once the process is completed. Once the water is added the lid is closed, to contain the smell, and the material allowed to soak for 3 day. The liquid should be  squeezed out of the sock or tights and used immediately, or at least within 24 hours.

Horsetail Tea Plant Feed

 Horsetail can be a nuisance on allotments as it is difficult to eradicate and while some might  want to grow it as medical or cosmetic herb it should be remembered that the next occupant of the plot will have inherited a problem or a very persistent weed. I advocate banning the deliberate cultivation on allotments, horsetail tea can form part of an eradication programme when the plant is present
Horsetail is high in silica and a when soaked to make a tea which, is said, to coat the leaves of treated plants producing a fungicide and protect against blackspot, mildew and mint rust. 

 Depending on the quantity of horsetail available it can either be soaked in a lidded bucket or a water butt (This is useful if allotment site plot holders are prepared to spend a day on an allotment wide horsetail harvest).

The plants need to be fully submerged under the water so  are best put in a sack or an old vegetable net  pinned down with a large stone or to suspend it in a submerged weighted bag .  Regular stirring is recommended. The fermentation process can range from  10 days to 3 weeks, depending on the ambient temperature. During fermentation the mixture will produce gas which will  bubble on the surface. Once the bubbling has stopped the  it has finished bubbling the liquid can be strained and used.

  • Fresh Horsetail soaking.

    The bucket contains some other weeds as it is as submitted by the plot-holder

  • Horsetail after soaking for 13 weeks

  • Close up of the horsetail after 13 weeks soaking

  • 4 months soaking

  • 6 months soaking

Nettle Tea plant feed


Cut young nettles to about 5cm above soil level. Crush the leaves by scrunching the stems in gloved hands or by placing them on a freshly mown lawn and using a mower to chop them.

Put the crushed nettles into a bucket, it does not matter if some grass is included with the neetles,  weigh down with a brick and  cover with water. Use about a half a standard bucket full (about one kilogram) of leaves to 10 litres of water. 

Nitrogen-rich nettles are high in silica. As with comfrey tea it is better to use a bucket with a lid to contain the smell. Allow to soak for 2 - 4 weeks.Stir occasionally.  The  liquid should be diluted to the colour of weak tea before being watered onto the plants being fed. 

There are two approaches to maintaining a supply  of feed throughout the summer. Either keep replacing the water as it is used and top up the supply of nettles ever two or three months. Or once the liquid is used add the  sludge to the compost bin, to help keep it moist and as an activator, and start again using the fresh growth that has replaced that which you cut.



Seaweed Plant Feed


Seaweed is a good  source of  potassium,  up to 12%, and trace elements but it is  low in nitrogen and phosphate. spraying is said to increase resistance to insect infestation. 

 To make a liquid seaweed brew soak the seaweed for about two months. It turns  brown as it decomposes and will produce a fishy smell when being used.

Compost teas

Information on Compost teas are given on the following page. Click here Compost Teas