Make Fertiliser – From Weeds!

The definition of a weed is a plant that’s growing somewhere it shouldn’t. Fair enough – you don’t want bindweed or dandelions in your vegetable beds. But weeds are not just a nuisance – they can prove incredibly useful in the garden.

I’m going to share how to use the power of weeds to make your garden grow stronger, including two super-easy methods for turning all kinds of weeds into an almost limitless source of free fertiliser to boost any plant, anywhere!

Recycling Weeds to Make Your Garden Healthier

All methods for turning ‘weeds’ into valuable gardening assets come down to simple biology. All plants take up nutrients from the soil which are then contained within their roots, stems, leaves etc. If we gather some of that plant material, we can unleash the goodness within it to help nourish other plants. It’s how nature does things – recycling nutrients time and again to sustain generation after generation of life.

Chop and Drop

Chop and drop is the simplest way to use weeds, and indeed any plant material. It’s exactly as it says on the tin: pull out your weeds, snip them up into smaller pieces, then just let them fall on the ground. By chopping them up we’re helping the plant tissues to break down and get incorporated into the soil that much faster.

You don’t have to drop weeds back in the same spot you gathered them – they can go on any area of soil. But there a few ground rules: chop and drop on a dry day so the weeds shrivel up and die before they can root back into the soil; use only seed-free weeds because you don’t want new weed seedlings popping up everywhere; and avoid the roots of creeping or perennial weeds.

Hoe, Hoe, Hoe

A hoe is ideal for severing the top growth of annual weeds while they’re still small, nipping the problem in the bud before it grows out of control. This too is a form of chop and drop – the sharp cutting blade of the hoe slices through the weed at ground level, cutting it two. The tops will fall onto the surface where they’ll wither, while the roots will decompose back into the soil.

If your garden has more than its fair share of weeds – and what garden hasn’t? – aim to hoe regularly, so you can gradually deplete the seed bank held in the soil. Just like when you chop down a purpose-grown cover crop or green manure, those severed weeds will be adding much-welcomed organic matter to the soil.

Feed the Compost Pile

You can also add weeds to the compost heap or bin too, and it’s where many of my bigger weeds like nettles end up. Fresh, green weeds contain are chock-full of nitrogen, making them a useful source of greens to balance out browns such as fallen leaves, woodier prunings, or torn-up cardboard.

There are several areas of my garden where the weeds are let be for much of the time, because, to be honest, I just don’t have time to keep up with them! But the flip side is I know I’ve got a ready supply of greens for the compost heap whenever I need them.

Again, make sure the weeds you gather are seed-free, and don’t add any roots from perennial weeds unless your compost pile gets hot enough to kill them off (about 140ºF or 60ºC). Add them whole or chop them up first to speed things along. I sometimes run my lawnmower back and forth over piles of weeds to break them down a bit.

Dry Weeds Out - or Drown Them!

Kill off pernicious weeds like bindweed before adding them to the compost pile by drying them out. I won’t lie – it can take a few weeks – but it does work. Lay them out on hard surfaces like paving slabs to desiccate in the sun. If you pop them in a heavily trafficked area to get trodden on repeatedly, they’ll soon give up!

The other option is to drown them – it all sounds rather macabre doesn’t it! But by submerging weeds they will, in time, dissolve into a sludge… which handily brings me on to that free fertiliser I mentioned at the start...

How to Make a Weed Tea

How about turning your weeds into a handy, free, quick-to-make, nutrient-rich, organic liquid fertiliser that will really supercharge your crops? There are two ways to do this, and the first way is to make a weed tea.

Different plants accumulate nutrients in different concentrations. To make a general-purpose feed that will suit a wide variety of crops use a mix of different types of freshly-harvested weeds, including the roots. By using different types of weeds you should get a broader range of nutrients to give a nourishing, all-purpose feed that you can use all around the garden.

If you have a specific plant or purpose in mind, you can make a tea from just one type of weed to major on a particular nutrient. Nettles are generally higher in nitrogen, making them a great choice for a feed that’s tailored towards leafy crops, while something like docks or comfrey will produce a feed with a slightly higher potassium content – ideal for fruiting crops like tomatoes. 'Single weed tea' sort of sounds like a single-estate coffee or a good single malt whisky, doesn’t it – very posh!

Get a bucket and squash your weeds down tightly into it. Pour in just enough water to cover the weeds and no more. Ideally, use rainwater for this, because it’s free of chlorine which you don’t want to add to your soil unnecessarily.

You could leave it at that, but if you want to speed the weed tea along you could introduce a host of beneficial bacteria by adding a natural, fermented food like yoghurt or – my preference – a small handful of mature garden compost or leafmould. This inoculates the water with a host of helpful microorganisms. Lovely stuff!

As it matures this sludgy liquid can develop quite the pong, so a lid of some type is advised! Cover your bucket loosely, because as the weeds break down and leach their goodness into the water, carbon dioxide is also released, and we want to let that gas escape rather than build up and potentially blow the lid off!

Leave your weed tea for 1-2 weeks to mature. Making a weed tea is quicker in warmer weather, because the bacteria helping to ferment the tea act that much faster.

Using Weed Fertilizer

After a week or two, the weeds will have reduced to a slop, making most weeds safe enough to plop onto the compost heap, leaving you with a greenish liquid.

Dilute one part weed tea to ten parts water to create a liquid feed to use just about anywhere: on and around vegetable crops, around ornamentals, bedding and container plants, or even to help new transplants on their way.

If you leave your tea to steep for longer, it will create a more concentrated feed. If you do this, dilute it a little further so it doesn’t overpower your plants. You can top up with fresh weeds and water as you gradually use up the tea, or simply start a new batch. Keep a succession of teas going so there’s always some at the ready.

Make Fertiliser From Weeds: Super-Concentrated Plant Feed

Another option is to make a concentrated liquid feed which can be bottled to save for later. Perhaps the most popular of these is a concentrated comfrey feed, which is ideal for fruiting crops, or you could use alkanet, which like comfrey draws up nutrients from deep down using its long taproot.

Get a bucket and make lots of holes in the bottom with a drill, then gather up the leaves – you’ll need to wear gloves for this because both comfrey and alkanet have sharp little hairs which can irritate the skin – and chop them up into smaller pieces and pack them tightly into the bucket.

Don’t add any water to your weeds this time. Instead, weigh the leaves down with something heavy like a brick or two to help them start breaking down. Pop a lid loosely on top.

As the leaves break down, they will exude a concentrated, black-brown liquid, which will collect at the bottom of the bucket and drip out of the holes in the base. To make sure every precious drop is collected, either lift the bucket up onto bricks and slip a collecting vessel underneath, or seat it inside another bucket. As the concentrate drips down, collect it from time to time and pour it into a bottle to store until it’s needed. Dilute just one part concentrate to 20 parts water, because it really is super potent!

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