Herbal and Plant Teas

Plant teas which can be applied by watering or spraying are a good source of nutrients

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

It is easy to make plant-based liquid feed extracts using comfrey, stinging nettles, horse tail or clover and seaweed. Compost and manure teas can also be made by soaking.

Comfrey Tea plant feed

Compressed Comfrey Tube.
The bucket would normally be covered with polythene to prevent it filling with rain water

Comfrey grows wild on many allotment sites as is a fast growing (and spreading) perennial) which will 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.

Either use a container with a tap, a hole in the bottom, so that the fertiliser drips into a catch-pot, or remove the liquid from above with a watering can. A 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 through out 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 has the advantage of not smelling anywhere near as much as the dilutes version. I recommend that it is made using a drainage pipe fiited 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 sparking wine bottle which is heavier and more fun to empty before use in the tube.

Larger quanitities of concenrated 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 compressing it 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)



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 through out 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.



Horsetail Tea Plant Feed

 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. 

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 Tea

The decomposed organic matter present in compost improves soil quality and provides nutrients for the plants. However the billions of bacteria, fungi, protozoa, nematodes and other micro organisms which form the living components of compost are often forgotten once they have completed their role in making the compost.  Conventional compost tea (extract) increases the benefits of composting as it acts a liquid fertilizer supplying soluble nutrients which can be used by plants.

Conventional Compost Tea (or Compost Extract)

Simple Compost watery extract has been made for centuries by suspending a burlap sack containing compost in a barrel of water for 7 to 14 days.

The technique has been modified slightly over the years using different water containers e.g. buckets or water butts, and means of filtering the liquid e.g. through a cheesecloth, pillow case or a pair of old tights. Another simple variation which makes stirring (aerating) the compost easier is to leave it loose in the water and filter at the end of the process. I use a short length of plastic drain pipe with the leg of a pair of tights over one end. 





Aerated Compost Tea


Aerated Compost Tea is a compost extract brewed with a microbial food source such molasses, kelp or rock dust. Aerated Compost tea (ACT) offers advantages over that made without the aeration. ACT has greater numbers of micro-organisms as the brewing process extracts beneficial microbes from the compost and enables them to multiply during the 24- to 36-hour brew period. Most of the descriptions of brewing aerated compost tea recommend the use of aquarium pumps with three bubblers below the surface of the liquid but this needs an electricity supply which few of us have near our compost bins.

 A cheap solar powered pond aerating pump is quite effective.

Half fill the bucket with compost and fill to within 3 or 4 inches of the top with water and add the aerator. Stir in about an oz. of black treacle (molasses). Stir regularly. After three days harvest the tea filtering through an old pillowcase, tea towel, or pair of tights.  The remaining solids can be put back into the compost bin.

 When first using compost tea dilute 1:10 and spray at least once a month, starting when plants have developed their first set of true leaves. To control damping-off, spray the soil with full-strength tea as soon as you plant. On trees and shrubs, spray two weeks before bud break, then every 10 to 14 days. 

Using Compost Tea

Compost Tea can be used:

1) Foliar spray adding beneficial organisms to plant so disease-causing organisms cannot find infection sites or food resources and to provide nutrients as a foliar feed.

2) Soil application to help develop the biological barrier around roots, to provide nutrients for roots to improve plant growth, to improve life in the soil in general, with effects on soil structure, water holding, root depth and improve nutrient cycling, nutrient retention and disease suppression.

 (The Compost Tea Brewing Manual Elaine R. Ingham, PhD.  Soil  Foodweb Incorporated) 

Worm Compost Tea

Put a shadefull of finished worm compost (roughly 1 gallon) into a pair of old tights, cheesecloth or pillow case into 5 gallon bucket of rainwater of one or two days or even just over night. Alternatively put the compost directly into the water and filter after soaking. I prefer this method as it allows the compost to be stirred or aerated more effectively than if it is contained in tights

Dilute until it is light brown in colour, not unlike week tea, and use immediately before the beneficial microbes in the start to die.

The sludge left in the bucket can be used on the garden or be added to the compost bin as a way of supply moisture and activator to the upper surface of the bin. 

Aerated Worm Compost Tea

Aerated worm compost tea is made in a similar manner to the normal Aerated Compost Tea (ACT) adding black treacle to the soaking compost to provide additional nutrients to encourage bacterial growth, and aeration to increase the population of the beneficial microorganisms.     

Put a shovel full (about 1 gallon) of  finished worm castings directly  into a 5 gallon bucket  add 4 gallons of rain water  and a tablespoon full of black treacle. Aeration can be by means of an electric aquarium filter of a solar powered pond pump.  Ensure the airstone is at the bottom of the bucket. I fix it in place by tying it to a stick or wire support.  Allow the tea to brew for 3-4 days, stirring occasionally.

Strain the tea using gauze, tights. I fix this over the end of a short length of plastic rainwater downpipe to make pouring easier and to allow the same filter to be reused.

Use the tea immediately to water your garden plants and seedlings or as a foliar spray.


Homemade Pesticides: Regulations

The following advice is taken from the HSE website. I have included it as background information as some homemade products, made in a similar way to liquid feeds, are  used as pesticides e.g. rhubarb leaves

Agricultural, horticultural and home garden pesticides are regulated under the Plant Protection Products Directive/Regulations and the Control of Pesticides Regulations.

Agricultural, horticultural and home garden pesticide products are those that are used to protect plants e.g. insecticides, fungicides, herbicides (weedkillers), molluscicides (slug killers), plant growth regulators and bird and animal repellents.

HSE are aware that some gardeners routinely use home-made remedies that are not authorised to control pests, diseases and weeds. In some cases these remedies are simple physical barriers and are outside the scope of UK and EU regulations. In other cases these remedies involve the use of chemicals either from foodstuffs, like coffee grounds, or from household products which are not normally intended to be used as pesticides.

Part of the legal definition of a plant protection product takes into account the intended use of the product. For example garlic extract sold as a foodstuff doesn’t require authorisation under plant protection product regulations but garlic extrac tsold as an insecticide does. In practice this means a number of own use home-made remedies such as beer traps or coffee grounds fall outside the scope of regulations.

However this does not mean that use of these remedies including use of common household chemicals as a pesticide is without risk or that it is always legal. For example in circumstances where a home-made remedy was supplied to another user (whether free of charge or not) this may fall in scope of the regulations, and if so would be illegal without an authorisation. In this sort of circumstance, where HSE (or other enforcing authorities) obtain evidence of such a supply or use we would need to consider appropriate and proportionate enforcement action.

Volunteer gardeners

An increasing number of members of the public are getting involved with allotment societies or volunteer groups taking on larger gardening projects which may previously have been undertaken by paid contractors. For example volunteer groups now manage parts of some public parks, take on ‘Britain in Bloom’ or similar projects and some allotment societies are now responsible for maintaining the whole allotment site rather than just individual plots. These activities span the borderline between amateur and professional uses of pesticides.

For further information