Nettle Liquid Manure: Preparation and Application

Nettle liquid manure fertilises and strengthens plants. That convinces every gardener. And best of all: it is very easy to make. Karl Ploberger shows you how to prepare and use the plant fortifier.

How is nettle liquid manure made?

To do something good for your plants, nettle liquid manure is the right choice. Making a stinging nettle liquid manure and extracting the sought-after plant juice is not complicated. Karl Ploberger tells you how to proceed and what you need to bear in mind. Just follow the instructions and nothing should go wrong.

Harvesting nettles

Nettles can be found wherever the soil is rich in humus and nutrients. Here they store valuable ingredients such as nitrogen, potassium, calcium and silicic acid. They release these again as liquid manure to other plants. For a stinging nettle liquid manure, harvest the plants before they flower or have seeds. For protection, it is advisable to wear sturdy leather gloves with high shafts. Otherwise you are guaranteed to come into contact with the stinging hairs!

Chop thoroughly

To ensure that fermentation takes place quickly, chop the plants into small pieces. The more carefully you chop the parts, the faster the nettle liquid manure will get going.

Use a wooden barrel (plastic also works) and rainwater to fill it up. Store the barrel in partial shade without closing it tightly at first. Instead, cover it with a net. The warmer the location, the quicker the conversion.

Tip: Put herb in a net (e.g. an old pair of tights). This way you can easily remove the plants after fermentation. The plant juice is then clear and can be used immediately.

Nettle, horsetail & co. are either fermented, boiled up or squeezed out. Water or spray the plants with the elixir.

Stir the nettle liquid manure regularly

Stinging nettle liquid manure announces itself when it is ready, so they say, because it begins to stink quite strongly. To bind the smell a little, sprinkle with primary rock flour. Stir regularly to speed up the fermentation process. The manure should be ready after two to three weeks in spring at low temperatures, and after one week in summer. Now close the liquid manure barrel with a lid and extract plant juice from it as needed.

Tip: No fresh herb at hand? Use dried nettle powder from a specialist shop or pharmacy.

Treating plants with nettle liquid manure

The finished liquid manure is diluted with water in a ratio of about 1:10 to 1:20. For herbs, lettuce and carrots, or for a fast-acting leaf fertiliser, increase to 1:50. Use your watering can without a spray head for watering and apply the diluted plant juice directly to the soil, never to the leaves. Water in the evening, because of the strong smell! Then cover the soil with mulch. Do not apply a slurry treatment too often, about every fortnight for strong eaters such as tomato, cabbage, celery, pumpkin, cucumber. Weak growers like peas, beans, onions and garlic do not tolerate it at all.

Plant liquid manure has often been studied by scientists. If you look at the analysis of the contents of a stinging nettle liquid manure, for example, you will see that in addition to fertilisers such as nitrogen and potassium, trace elements and growth substances (hormones) are also present in small quantities. The special effect of the liquid manure is hidden: They can make minerals that have been fixed in the soil available to the plant roots. The root system itself is promoted. This can be seen in the vigorous growth of the plants. Pale, light green leaves turn rich green again and are bursting with vigour.

Recipes for plant strengthening agents

Liquid manure (as fertiliser and to strengthen plants)

Grind 1 kg of fresh or 100-200 g of dry herb (e.g. comfrey, nettle, marigold). Prepare in ten litres of cold water, but not in metal containers! Stir every day. The liquid manure is ready after one to three weeks. It is then dark and no longer foams. Dilute to 1:10 to 1:20 (for foliar fertilisation dilute to 1:50).

Broth (for pest repellent and plant strengthening)

From plants such as horsetail, horseradish or tansy, grind 1 kg fresh (100-200 g dry herb) and soak in rainwater for 24 hours. Then simmer for 30-45 minutes. Allow to cool, strain and spray over plants undiluted or in a ratio of 1:5. Fomentations and broths can only be kept for a short time.

Tea (to repel pests and strengthen plants)

Pour hot water over fresh or dried herb and let it steep for 30-60 minutes, covered. Then strain, allow to cool and usually spray undiluted over the plants. Tea of sage and thyme repels pests, garlic tea prevents mildew and other fungal diseases. Cold water extracts (to repel pests and strengthen plants) are suitable where fermentation or heat would destroy the valuable ingredients (e.g. camomile). Soak in cold water for 24 hours, squeeze out herb. Diluted 1:1 or undiluted, pour or spray. Extracts do not last long, use up the same or next day.
Tried-and-tested plants for decoctions, broths and teas

Here are the “fantastic four” from the list of suitable plants:

Nettle: its leaves make an excellent mulch. Fermented into liquid manure, it is a natural nitrogen fertiliser for vigorous vegetables and hungry herbs (mint, basil). Besides root and plant growth, it also promotes soil life. As a tea it is good against aphids.

Tansy: Its ingredient pyrethrin is a contact poison that paralyses insects – unfortunately not only the unwanted ones! Although it is considered ineffective for humans, mammals and birds, eat treated vegetables and fruit only after three days!

Field horsetail: No herb prevents fungal diseases better. The silicic acid is incorporated into the cells of treated plants. This makes the cell walls stronger. Fungi and insect pests literally bite their teeth out. Spray as a broth on cucumbers, courgettes and roses as a preventive.

Comfrey: Formerly valued as a remedy for wounds and broken bones, today organic gardeners enrich the soil with nutrients (potassium) using the slurry. Promotes tuber/fruit formation in tomatoes, potatoes and berries.

Nettle manure and use in the garden

Fungus-free orchard: Field horsetail liquid manure is considered the best preventive fungicide. It is said to be effective against mildew, late blight, apple scab, monilia, rust and star sooty mould, for example. Wormwood liquid manure has a reputation for driving away insect pests and repelling currant stem rust. It is best to reapply these biological plant protection products to the root zone after each rain or to spray on infested leaves.

Aphid-free ornamental garden: To keep roses growing vigorously, fertilise with nettle liquid manure and repeatedly spray with horsetail broth. Sage or thyme tea will scare away ants. Nettle tea or extract helps against aphids. Spray undiluted on the upper and lower sides of the leaves. Repeat the application weekly.

Healthy vegetables: Besides stinging nettle liquid manure, comfrey liquid manure is the best for the vegetable garden. It contains a lot of nitrogen and potassium as well as trace elements. The recipe: ferment 1 kg of fresh comfrey leaves or 150 g of dried leaves with two handfuls of marigold leaves and flowers in 10 litres of water. Ideal for fruit vegetables, also as a compost addition. Use 1 x per week diluted 1:10.