Uses for Weeds – Liquid Fertiliser

edible weeds, dandelion, root, stem, leaves, taraxacum officinale

As the days grow longer the plants in our gardens send up new green shoots and flower buds. A delight to the eyes. Less delightful are the weeds that also push up through the soil.

Gardeners are rightly reluctant to throw the roots and stems of perennial weeds onto the compost heap. Many of these plants have the ability to propagate from just a small section of stem, and the nutrient rich atmosphere of a healthy compost bin would offer perfect growing conditions.


Uses for Weeds – Liquid Fertiliser

Let’s consider two perennial garden weeds in particular: Dandelion and Green Alkanet.

Did you know that the pulled up and dug out stems, leaves and roots of both of these weeds can be turned into a home-made liquid fertiliser?

Both nettle and green alkanet have tap roots, which go deep into the soil. As you will have discovered when you come to pull them out!

This can be turned to your advantage. Those deep tap roots have taken valuable minerals and nutrients from the soil and stored them in their roots. When you pull up these weeds and simply throw them out, you toss out the minerals and nutrients as well.



Dandelion, Taraxacum officinale, has a long strong tap root from which it can easily regrow if a piece is left in the ground. Its flower is made up of lots of smaller florets, all of which go to make the impressive spherical ‘dandelion clock’ or seed head. The individual seeds blow on the wind and generally carry the same DNA as their parent, as most dandelions reproduce asexually.

Although considered a weed when found in most gardens, the dandelion has a long history as a medicinal and culinary herb. For example, you could make wine from the petals, tea and salads from the leaves; coffee and soup from the roots.


Green Alkanet

Green Alkanet, Pentaglottis sempervirens, is a native of South Western Europe and seems to have been introduced in to Britain before 1700, probably during the Middle Ages. Like Dyers Bugloss, Alkanna tinctoria, for which it is frequently mistaken, green alkanet has roots which can be used to produce a red dye.
The stems and leaves are covered with hairs which are a skin irritant, so care should be taken when pulling up this weed.

Green alkanet does have pretty blue flowers very similar to Borage flowers. This is probably why it has spread so easily, as it may have been mistaken for the prettier, edible plant.


Uses for Weeds – Liquid Fertiliser – What is it?

Liquid fertiliser, also known as fertiliser tea, or weed tea, is made from fresh plant material. This is different to compost tea, which is a liquid made from composted material.

Dandelions and green alkanet have nitrogen, phosphorus, potassium, magnesium, boron, copper, manganese, sulphur, iron and silicon in their roots, stems, leaves and flowers.

The solution you’ll create from the rotting greens and roots will be a leachate. In this circumstance, it means a liquid which has extracted the soluble material, the nutrients, from the weeds.

It has a short ‘shelf life’. Aim to use it within a month, certainly within the same growing season.

Remember this is not a drinkable brew for humans!

green alkanet, hairy stem, blue flowers, Pentaglottis sempervirens, perennial weed, hairy leaves, skin irritant


Uses for Weeds – Liquid Fertiliser – How to make it

This is just one, simple method. Fairly fool proof though. Although we’re using it for two particular weeds, there are many other plants and weeds form your garden which are suitable. More on these another time.

  • Use a bucket with a lid to put your dandelion and green alkanet weeds into
  • It shouldn’t be air tight as the fermentation process releases carbon dioxide. Which could blow the lid off – you don’t want an exploding bucket of smelly liquid fertiliser…
  • Pack the weeds down as tight as possible
  • Continue filling until the bucket is around two-thirds full of tightly packed weeds
  • Adding a preservative-free fermented food such as yoghurt will speed up the process, but isn’t essential
  • Top up the bucket with rain water
  • Leave the weeds to ferment in the bucket of tea somewhere warm for a week or two


Uses for Weeds – Liquid Fertiliser – How to use it

Before using, it is an idea to strain the weed fertiliser tea through a piece of cloth. This ensures you don’t disperse weed seeds or clog the nozzle of the watering can with bits of rotted weed.

Water-soluble homemade fertilizers are short acting rather than slow release. They should be applied no more than every two weeks, usually as a thorough soaking.

The solution can be strong, so it is advisable to dilute it as you would a shop bought liquid fertiliser. The ratio 1:10 is a good one to start with. Due to the differing content of weeds and nutrients in each ‘batch’ of weed tea, it’s not possible to be definitive, so err on the side of caution. The colour should be similar to a weak black tea.

Where to use it

  • Bedding plants which put on a lot of growth over a short season
  • Container plants
  • Vegetable plot – not immediately before harvest; then it should be water only
  • Ornamental shrubs, herbaceous perennials
  • Seedlings in nutrient poor growing media may benefit from a ‘drink’ before being transplanted to a richer soil. Dilute the liquid fertiliser further when using it on seedlings

A word of warning – avoid spilling any weed fertiliser tea on your hands or clothing. It smells horrible and the smell lingers!

edible weeds, dandelions, nettles, lawn,urticaria dioecia, taraxacum officinale


Uses for Weeds – What else?

By steeping the weeds in water and using the result as a liquid feed in your garden you resolve at least part of the weed problem.

Are there other ways in which you can turn dandelion and green alkanet into something useful for your garden? And other weeds? To which the answer is ‘yes’. But that’s another blog…

Why not read our other weed blogs for more ideas and information?

And if you feel a garden advice visit would be beneficial for you and your garden, please get in touch. Marie is a member of the Professional Garden Consultants Association.


Related Gardening Blogs from Plews Potting Shed

Edible Weeds
Weeds – Ground Elder
Weeds – Ivy and Bindweed
Weeds – Japanese Knotweed and Rhododendron

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