Nettle: A Plant with Many Benefits

Nettle manure, the garden's magic potion

Nettle tea, more accurately called fermented nettle extract, is obtained through the aerobic fermentation of its leaves and stems over one to three weeks.

This fermentation process releases the active compounds from the plants. Often described as a foul-smelling concoction, properly prepared nettle tea is practically odourless, clear, and easy to store.

Nettles are renowned for strengthening plants, stimulating soil microbial flora, enhancing compost ripening, and improving chlorophyll function.

That’s why this potent elixir is used as a preventative treatment against diseases and as a natural fertiliser. It eliminates the need for harmful chemical products that damage the environment… and it’s free!

Fermentation couldn’t be simpler—just steep the plants in water for several days. The only risk? Botching the process and ending up with putrefaction instead of fermentation, resulting in a brownish, ineffective, and foul-smelling liquid. Properly fermented extract has a tolerable odour. Don’t worry—the recipe is incredibly easy… We’ll guide you step by step in this tutorial: “How to Make Nettle Tea“.

If the idea of brewing a stinky liquid puts you off or you lack the time, you can also buy it ready-made! Ready-to-use nettle tea, diluted in water, is available—ideal for urban gardeners who struggle to source nettles or those with small gardens requiring only small quantities.

The uses of nettle as a liquid fertiliser

While nettle tea has not yet been scientifically proven to be beneficial on a large scale, it remains a favourite among organic gardeners who take pride in growing their vegetables naturally, without chemical fertilisers or pesticidal products. In both the vegetable patch and ornamental garden, it can be used as:

• Fertiliser, plant food

Nettle tea, due to its high nitrogen concentration, is often considered a natural fertiliser that stimulates plant growth and promotes the development of stems, leaves and roots.

In reality, it’s worth noting that the term ‘natural fertiliser’ isn’t entirely accurate, as its levels of nitrogen, phosphorus and potassium may not be sufficient for it to be classified as such. Nevertheless, nettle tea remains effective, but rather as a phyto-stimulant.

Indeed, many gardeners observe accelerated growth leading to earlier plant development, not just in leafy vegetables but also in tomato plants, which would flower and fruit earlier – particularly useful in regions with short summers.

It’s also important to remember that nitrogen promotes foliage at the expense of flowering. This is why we recommend using nettle tea as a watering solution only during the first few weeks after planting to encourage vegetation. Afterwards, if needed, switch to comfrey tea, which will instead encourage fruit production.

• Pest repellent, including aphids

Plant extracts are not true pesticidal products as they don’t eradicate pests. They simply disrupt certain insects’ orientation, limiting invasions by hindering their mobility, reproduction and feeding. Some plant extracts contain molecules that encourage plants to produce substances making them unappetising, while others may contain molecules affecting the pest’s metabolism. Prepare a fresh leaf maceration for 12 hours (1kg per 10 litres of water). Apply diluted at 10%, meaning mix 1 litre of nettle tea with a 10-litre watering can of water, preferably rainwater.

Nettle tea helps combat aphid colonies

• Stimulant for plants’ natural defences

Plant extracts trigger plants’ immune defences, stimulating and improving mineral absorption. But always ask yourself beforehand whether intervention is necessary. If a plant remains healthy, why stimulate its natural defences? Does it really need it?

In a naturally cultivated vegetable garden where biodiversity is preserved, pesticidal and chemical fertilisers are banned, and the soil is protected – in short, under good conditions – plants rarely become diseased. And if a pest attack occurs, beneficial insects limit the damage, as do insect nets for example. There’s no need to treat, even with plant extracts, unless necessary. However, if after a particular event (hailstorm, heatwave, etc.) plants become weakened, you can spray fermented nettle extract diluted to 20% (1 litre of nettle tea to 5 litres of water) to help them react quickly to the stress.

• Anti-iron chlorosis

Chlorosis causes leaf discolouration. This phenomenon isn’t due to iron deficiency in the soil but rather to blocked assimilation, often caused by excess lime. Nettles contain good iron levels. Spraying with nettle tea diluted to 5% or 10% as a watering solution may eliminate symptoms, thanks to bacteria making iron assimilable by plants – though this doesn’t solve the underlying issue. It’s essential to undertake deeper work to maintain the most living soil possible, particularly by regularly amending it with organic matter.

• Compost activator

Plant waste after filtering – and even leftover nettle tea (unfiltered) – can be added to the compost heap. Nettle tea is reputed to activate and accelerate the decomposition of compost waste.

• Weedkiller

Undiluted nettle tea is considered a good natural weedkiller. Beware – used this way, it’s also polluting. Indeed, its high nitrogen content causes nitrate accumulation (from nitrogen nitrification) in the soil, creating significant toxicity for fauna and flora. This inevitably harms biodiversity. Let’s remember that products, even natural ones, should not be used indiscriminately!

Other uses of nettles

• Nettle, a pillar of biodiversity

Often disliked and considered a “weed”, the nettle is nevertheless invaluable in gardens, particularly those with an ecological focus. Indeed, it’s a host plant for a multitude of insects, including several caterpillar species such as the Peacock Butterfly or the Small Tortoiseshell.

Therefore, always remember to leave a small wild corner for nettles in your garden: wildlife will thank you for it!

Left: Small Tortoiseshell caterpillar (Aglais urticae) – Right: Ladybirds’ mating season.

• Nettle, a medicinal herb to try in cooking too

Delicious in soups, nettle is packed with vitamins and minerals. It can also be used as a diuretic and anti-bacterial herbal tea, and even to stimulate hair growth!

In cooking, it enhances many dishes such as salads, quiches, cakes, cookies and can even be enjoyed as pesto!

Nettle cake (credit: Association Cueillir)

To learn more :

• “Nettle Teas and Friends” published by Terran.
• “Revolution in the Vegetable Garden” by Guylaine Goulfier.
• Our tutorial: Make Your Own Nettle Powder