Better than MiracleGro - Make Fertilizer from Nettles

Every year gardeners spend a fortune on fertilisers when the best plant food can actually be made for free – from weeds you’re pulling up! Homemade organic fertiliser is the best nutrient boost for all kinds of plants around the garden, so I’m going to demonstrate how to make not one but two incredible plant feeds in next to no time.

Gather Your Nettles

Nettles are not only easy to find, but just happen to be full of nutrients too. They have extensive roots that are highly efficient at drawing up nutrients from the soil, so why not recycle those nutrients into fertiliser for the plants you want to grow?

Our first job is to gather some nettles to make our plant feeds. Young nettles, or the softer tips of more mature ones, are packed with soluble nutrients, amino acids and naturally occurring plant growth compounds that are at their highest concentration when the plants are growing vigorously.

The ideal time to harvest is in spring or early summer, before the nettles begin to flower, but you’ll often find fresh new growth later in summer or even the autumn, particularly after a prolonged dry spell when the return of steady rains can lead to a welcome burst of fresh new growth.

Once nettles start flowering, much of their energy diverts into producing seeds, with the result that stems can become tougher and more fibrous, with a lower concentration of the compounds and nutrients we’re after. If your nettles have already flowered, don’t worry – they’re still perfectly usable – but for the very best results, aim for fresh green shoots around 1-2 feet (30-60cm) tall.

Try to harvest nettles early in the morning if you can, as soon as any dew has dried but before the heat of the day has built up. At this point the leaves are fully hydrated and contain the maximum amount of cell sap. Avoid harvesting in the middle of a hot afternoon, when plants can become water stressed.

I like to collect nettles wearing, of course, a stout pair of gloves to avoid any stings, and using a pair of sharp scissors. Cut the top growth from the plant, taking the soft growing tips and young leaves rather than the older woody stems further down. Not only are these the richest part of the plant, but leaving the lower stems intact allows the nettles to regrow quickly, so you can make several harvests from the same patch throughout the season.

Avoid nettles growing beside busy roads, on industrial sites, or from areas that may have been sprayed with herbicides or contaminated by chemicals. As with anything you’re using in the garden, the quality of what goes into your feed determines the quality of what comes out.

How to Make a Liquid Feed From Nettles

Once you’ve collected your nettles, it’s time to turn them into a potent liquid feed, or nettle tea. All we need is a bucket, plenty of fresh nettles, and enough water to completely cover them over. There’s no need to be too precise – simply pack the bucket with your nettles and push them down as you go to ensure they’re properly packed in.

Fill the bucket with water to completely cover the nettles, ideally using collected rainwater, but tap water is fine too. Put on a lid, and leave nature to get to work.

Over the next two to four weeks, the nettles will slowly break down, releasing valuable nutrients like nitrogen, potassium, and trace elements into the water. Give it an occasional stir if you remember, and be prepared: as it ferments, the smell can get a little, well... earthy! I personally don’t mind it – it’s a strong smell, but it makes you feel alive! This stuff has been used by gardeners for generations despite the smell, and for very good reason.

How to Use Nettle Tea

When it’s ready to use, the liquid should be a very dark green, almost black, and the nettles will have collapsed into a soft, slimy mass. The first job is to strain out the plant material and throw it onto the compost heap, where it will still has plenty of value. Don’t worry – because those nettles have been wallowing in water for so long, there’s no risk that they’ll take root in your compost.

What we’re left with is a concentrated liquid feed, which is far too potent to use neat. Dilute it at about one part nettle tea to ten parts water. If you are feeding young or delicate plants, err on the side of caution and make it a little weaker than this.

Then simply water it around the base of your crops every week or two during the growing season. This is a simple and free way to recycle one of many gardens’ most abundant weeds into a nutrient-rich feed that your vegetables, flowers and hungry plants will absolutely love.

Make a Concentrated Plant Stimulant

And now for our second natural, organic fertiliser, which makes a superb alternative to the more traditional nettle tea, and it’s a lot less smelly too! If traditional nettle tea is the hearty home-cooked meal, this next one is more like an espresso shot. It packs a punch! What we’re going to make is a Fermented Plant Juice, or FPJ for short, and although it also starts with nettles, it’s going to work in a completely different way.

Instead of soaking our gathered nettles in water, we’re going to chop them up and mix them with an equal weight of brown sugar. The sugar immediately starts drawing the sap out of the plant cells, and over the next five to seven days, that sap naturally ferments into a beautifully concentrated liquid – without the pong!

But unlike nettle tea, this isn’t really about feeding your plants with lots of nutrients. Instead, it’s all about capturing the nettle’s natural growth-promoting compounds – things like amino acids, enzymes and plant hormones that help plants make better use of the nutrients that are already in the soil.

Massage your nettles and brown sugar together as best you can, giving everything a good mix, then put it all in a glass container. Loosely cover it and leave it somewhere cool and out of direct sunlight.

Before long you’ll notice a rich, dark liquid collecting in the bottom. That’s the fermented plant juice. Once it’s ready – after no more than a week – this liquid can be strained off and stored in a clean bottle.

How to Use Fermented Plant Juice

Now here’s the bit that catches everyone out. This concentrate is incredibly potent, so we only need a tiny amount. That means a little goes a very long way, so we dilute it to just one part FPJ to around 500 parts water – or 20ml to a watering can that holds two gallons or 10 litres. That may sound weak, but remember – this isn’t a fertiliser, it’s a biostimulant. We’re not trying to feed the plant, we’re just giving it a gentle nudge to root better, grow more strongly, and make the most of what nutrients are already available.

There are two ways to use Fermented Plant Juice. The first is as a soil drench. In other words, simply pouring it around the base of your plants, just as you would any other liquid feed. Although you’re not adding huge amounts of nutrients, what you are doing is introducing all those naturally occurring plant compounds into the soil where they can support both the plant and the beneficial microbes living around its roots.

The second option is to use it as a foliar spray, and this is where FPJ really comes into its own. By spraying a fine mist over the leaves, the plant can absorb some of these small, biologically active compounds directly through its leaf surface. It’s a quick and efficient way to give plants a boost, particularly during periods of rapid growth or after they have been knocked back by transplanting, dry weather or other stresses. Aim to spray in early morning or early evening when it’s cooler. This will give the tiny droplets longer to sit on the leaves before they evaporate.

You don’t need to use FPJ every time you water. Applying it every week or two during the growing season is more than enough. This is one of those situations where less is actually more. Plants only need genuinely tiny amounts of these natural compounds, so resist the temptation to make it stronger. In fact, using too much is more likely to reduce the benefits than improve them.

Fermented Plant Juice is not a replacement for healthy soil, regular watering and balanced nutrition. Think of it as another useful tool in the gardener’s toolbox. It’s a simple, natural way to give plants a gentle helping hand when they’re growing their hardest.

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