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Comfrey manure as an organic fertilizer: a guide

02.06.2023  /  Reading time: 8 minutes

Comfrey liquid manure is a great way to provide your plants with additional nutrients alongside nettle liquid manure and other plant liquids. In addition to nitrogen, comfrey provides your plants with potassium and phosphorus in particular, which benefits their growth. You can find out how to make and use comfrey liquid manure in this article.

This article contains:

  1. Plant manure as an organic fertilizer for your vegetables
  2. Make your own nitrogen fertilizer from comfrey plants
  3. Prepare comfrey liquid manure: This is how it works
  4. Comfrey: effect & application
  5. Calcium & potash fertilizer for tomatoes
  6. Fertilizer for cucumbers, potatoes & other heavy growers
  7. Frequently asked questions about making comfrey liquid manure

Quick Overview

Make & use comfrey liquid manure

  • Put 1 kg of chopped leaves and stems of comfrey (possibly also marigolds, nettle & rock flour) in a large bucket (not metal) and fill with 10 liters of rainwater.
  • Cover with a lid or cloth and stir with a stick every 1-2 days.
  • As soon as the slurry no longer foams when stirred, it is ready (takes between 1-3 weeks).
  • Water your plants from below with diluted liquid manure every 1-3 weeks.
  • Especially heavy growers such as tomatoes, cucumbers, pumpkins and potatoes are happy about the fertilizer.

Effect and use of comfrey in the garden

  • Supplies your plants with nutrients.
  • Contributes to humus formation & healthy soil through microorganisms in the slurry.
  • Protects your plants against pests (spider mites, aphids & mildew) by spraying, as the leaf structure is strengthened by silicic acid & silicon.

Plant manure as an organic fertilizer for your vegetables

Prepare comfrey liquid manure
All types of comfrey are suitable for making a plant slurry. This includes the rough comfrey(Symphytum asperum) shown here. Picture by Hans on Pixabay.

Plant dips are natural fertilizers that you can easily make yourself from plants in your garden. They provide your vegetables with additional nutrients quickly. You also contribute to a healthy nutrient cycle. The nutrients extracted from the soil by plants such as nettles and comfrey are returned to the soil and your plants. In addition to nutrients, plant dips also contain many effective microorganisms (through the fermentation process) that contribute to soil improvement (decomposition and conversion processes, humus formation, improvement of the soil structure). You also save money, as these natural fertilizers cost you nothing apart from a little water and effort. You can find out more about natural fertilization in the article on natural and organic fertilization.

Make your own nitrogen fertilizer from comfrey plants

In addition to their use as medicinal plants and ground cover (in permaculture, e.g. under tree slices), comfrey plants, just like nettles, bind a lot of nitrogen from the soil. Comfrey manure is therefore an excellent nitrogen fertilizer for your plants. In addition to nitrogen, comfrey also contains relevant amounts of potassium, calcium, phosphorus, trace elements, silicic acid and tannins.

If you don't already have comfrey in your garden, you can sow and plant it as a ground cover or bee-friendly plant in your garden. You can find out what you should bear in mind in our article on sowing, planting and harvesting comfrey. Otherwise, you can also often find comfrey along streams and at the edges of paths and woodland.

To have enough comfrey available for the fall or next year, you can dry comfrey, nettles and the like. You can then simply make slurry with the dried plant parts as soon as you need a fertilizer for your plants.

Prepare comfrey liquid manure: This is how it works

Preparing plant manure: instructions
Comfrey liquid manure is prepared in the same way as nettle liquid manure. Place the leaves and stems in a large bucket, fill with rainwater and cover with a cloth or lid.

The stems and leaves of comfrey contain the most nutrients, which is why they are best suited for making slurry. Comfrey (Symphytum officinale), comfrey (Symphytum peregrinum) and Caucasian comfrey (Symphytum asperum) are all suitable for making a plant slurry.

You needone kilogram of comfrey to make about ten liters of liquid manure. To do this, you should chop up the stems and leaves a little so that they decompose well and start to ferment. You can also add nettles and marigolds to the container. They contain additional nutrients that your plants will enjoy. Rock flour is also a popular addition, as it binds the strong odor during fermentation.

It is best to use a large bucket to make your comfrey fertilizer. Do not use metal objects as containers or for stirring, as the slurry becomes highly acidic during the fermentation process. This can corrode the metal and release unwanted metal ions that can be harmful to the environment. Once you have filled the bucket with the comfrey leaves and stems and an appropriate amount of water (preferably rainwater, tap water is less suitable), cover it with a cloth or lid. This prevents insects from accidentally falling into the liquid manure and drowning. However, your container must never be sealed airtight, as gases are released during the fermentation process and need to escape. Stir the slurry every 1-2 days. It will take between 1-3 weeks until fermentation is complete and your comfrey slurry is ready. You can tell that the slurry is ready for straining by the fact that no more foam forms when you stir it.

Comfrey: effect & application

Plant soaks as a compost starter
Not only can you use plant liquids as fertilizer and plant protection for your plants, diluted liquids are also ideal as a compost starter. Comfrey leaves can also be used as a compost accelerator. Picture by Herbert on Pixabay.

Plant dips not only provide your plants with nutrients, they also help them to become more resistant to pests and diseases. Above all, the nutrients and microorganisms contribute to the formation of humus and thus to healthy soil. Water your plants from below, as the liquid manure is too concentrated for leaves and will otherwise damage them due to the acidity. However, certain plant liquids are used specifically against pests by spraying the leaves of your plants with diluted plant liquid. In the case of comfrey and nettle, the liquid manure is diluted by a factor of 1:20 if you want to spray the leaves with it. The silicic acid and silicon contained in the liquid manure strengthen the leaf structure, giving the leaves a firmer surface. This protects against bacterial diseases and sucking insects in particular, but less so against viruses. Comfrey manure, for example, strengthens resistance to spider mites, aphids and mildew. You can find out more about this topic in our article on Naturally strengthening plants without chemicals.

Calcium & potash fertilizer for tomatoes

Tomatoes need a lot of potassium and calcium for their development. Especially in this combination with potassium and calcium, and as a fertilizer for the soil, as well as for spraying leaves, comfrey liquid manure is very suitable for tomatoes. It strengthens the fruit and prevents fruit rot and other fungal diseases. As tomatoes need a lot of nutrients, you can water them once a week with the plant liquid manure. They will appreciate the additional nutrients that comfrey provides. By fertilizing with liquid manure, you also avoid over-fertilization, which happens more quickly with conventional fertilizers.

Tip: If you add marigolds to the liquid manure as well as comfrey, you will also increase the potassium content of your plant liquid manure.

Marigolds as plant protection
Marigolds as an additive to plant liquids bring additional nutrients into the liquid manure and strengthen the resistance of your plants. Image from Светлана on Pixabay.

Fertilizer for cucumbers, potatoes & other heavy growers

In addition to tomatoes, comfrey liquid manure is particularly suitable as a fertilizer for heavy growers such as eggplants, cucumbers, pumpkins, potatoes, peppers, celery and zucchinis. But berry bushes, lovage, fruit trees, roses and sunflowers are also happy to receive such fertilizers. You can water your plants with the liquid manure every 1-3 weeks as required. Instead of a slurry, you can also bury the leaves of comfrey in the soil next to the roots of your plants or mulch them with it. This will release the nutrients to your plants more slowly, but continuously over a longer period of time.

Produce your own phosphorus fertilizer

Comfrey manure also contains plenty of phosphorus, which is important for the formation of flowers and fruit. Plants that have a high phosphorus requirement, such as lemons, mint and hydrangeas, benefit from a dose of comfrey fertilizer.

Harvesting comfrey
Comfrey can be harvested up to four times a year. However, you should stop harvesting at the end of August so that the plant has enough strength to survive the winter. Image by Annie on Pixabay.

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Cover picture by Couleur on Pixabay.

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Marielena studies agricultural and environmental sciences. She gardens at home and at an allotment and likes to try out new things. She loves to spend time in nature during gardening, bird watching and photographing, hiking and camping.

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You need about 1 kg of stems and leaves, which you mix with about 10 liters of rainwater in a bucket (not metal). It is best to stir the slurry every 1-2 days. It is ready as soon as no more foam forms (approx. 1-3 weeks).

Before use, you should dilute the liquid manure with water (1:10). It is suitable as a fertilizer for heavy growers such as cucumbers, potatoes, cabbage, pumpkin, tomatoes, but also for berry bushes, fruit trees, sunflowers, roses and lovage.

You can fertilize your plants with the slurry every 1-3 weeks as required. Tomatoes particularly benefit from a weekly application. However, make sure to dilute the comfrey liquid manure with water at a ratio of 1:10 beforehand.

You can provide your plants with additional nutrients for a whole season with prepared comfrey manure. Next year, however, you should prepare a new slurry, for which you can also dry the leaves and stems.

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