Homemade Eco-friendly Garden Fertilizers

As the Northern Hemisphere moves from Spring to Summer, your gardens will take a huge chunk of time to feed plants, control pests and diseases and generally keep them looking their best.

As my garden takes a rest, I thought I would share some simple, environmentally friendly, but effective homemade, non-toxic fertilizers for the garden using things that most people have around the house.

I’ve used the knowledge that my grandparents passed on to me: one was a keen gardener in inner-city Sydney, who had a double block of land and so was able to feed his family throughout the great depression and strict rationing of WWII, and the other was a farmer on 100,000 acres of land in North Queensland who also had to produce crops during the same tough era.

I’m only including the remedies that I have used and have seen work.

The N-P-K values are indicative only; changing the volume of ingredients or the amount of water used will alter the N-P-K results dramatically, as will the growing conditions of the plants – for instance weeds grown in rich soil will have a higher N-P-K than those grown in poor soil.

N-P-K is the standard Nitrogen-Phosphorous-Potassium ratios that you see on the back of all fertilizer products in the store. Put very simply, Nitrogen promotes leaf growth, Phosphorous promotes root, flower and fruit growth and Potassium promotes overall plant health and disease resistance.


Liquid Fertilizers.

The best way of ensuring your plants aren’t attacked by pests and disease in the first place is to have good soil, with the right plant in the right place and then to ensure that it is adequately watered and fed.

Because that’s not always possible, one of the best ways to give plants a boost is to apply liquid fertilizers. The results are very fast acting.

  • Comfrey Tea.

comfreyComfrey is invasive and difficult to eradicate – so grow it in pots. To the make the tea is simple:

Grab at least 15-20 leaves, tear them loosely & place in a one litre (1/3 gallon) bucket; fill this with water in a shady, out-of-the way corner for at least one month. The bucket should be loosely covered. Stir at least once each week.

Once it has become a horrible, stinking swill, you dilute it between 1:10 to 1:4 (depending on your needs, 1:10 would be for seedlings, pot-plants and newly transplanted plants, 1:4 would be for established trees and shrubs or established, stressed perennials, etc) in a watering can and use it in place of commercial seaweed products.

A 1:10 diluted comfrey tea has an N-P-K value of N 0.02 – P 0.007 – K 0.04.

A 1:4  diluted comfrey tea has an N-P-K value of N 0.08 – P 0.03 – K 0.2.

Compared to a seaweed emulsion, this looks very weak: (A commercial seaweed solution is N 0.1 – P 0.01 – K 1.8) but those products are designed to be used only fortnightly: comfrey tea can be used more regularly. Comfrey is a good solution to promote consistent, continuous flowering and fruit production. Also higher N-P-K values can often be misleading as they are simply leached into the soil and ground-water. A plant can only use so much fertilizer at a time!

  • Weed Tea

weedMade exactly the same way as comfrey tea, only there will be 1:1 weeds to water ratio and, depending on the weeds or other green matter used, Nitrogen values can be much higher, thus promoting leafy growth.

Given how many different weeds there are, I can’t give an N-P-K value for this. Ensure that any weed tea is sufficiently diluted (at least 1:10) to avoid salt and alkaloid build-up (present in many weed species). For gardeners in the UK/Europe, nettles are a great source and can yield an N 0.15 – P 0.05 – K 0.4.

  • Molasses Tea

molassesThis is a good soil amendment and promotes microbial activity as human grade molasses also contains a lot of other trace elements. Mix 1:10 with hot water. Once cooled gives an N-P-K of 0.7  – 0 – 4.5, so use sparingly. In humid climates it is best applied to the soil as foliar application can promote sooty mould.

  • Moss Tea

mossOnce you have thatched the lawn, or peeled it off slippery pathways, mix it with boiling water to avoid spreading moss spores.

When diluted 1:10 should yield an N-P-K of 0.06 – 0.01 – 0.06

  • Deciduous Oak Leaf Tea

leafWhen diluted for a month (70% leaves : 30% water) will yield an N-P-K of roughly 0.008 – 0.003 – 0.001 which is a very gentle tonic that is suitable to use on seedlings.

Regardless, oak leaves make the best humus, so plant an Oak tree today 🙂

  • Tea Leaves

teaReuse the last dregs in the pot by re-filling with boiling water. Once cooled, the N-P-K is 2 – 0.3 – 0.2. Tea is good for grasses and other leafy plants. Tea leaves are also good worked straight into the soil. There is some concern over allelopathic potential with tea and coffee, but I have never seen plants stunted when using tea leaves – especially when used sparingly and in the ground (rather than pot plants).

  • Milk

Milk

A favourite of mine as I rarely get through a whole carton of milk before the use-by date. Once your milk is past its use-by-date, mix it 1:1 with water to be used as a foliar spray. Diluted milk has an N-P-K of 0.25 – 0.15 – 0.1 and also provides a quick calcium hit. The microbes that break down the fat and lactic sugars are also great for the soil.

Milk also has other pest and disease benefits, such as controlling aphids, curtailing blossom end rot and has anti-fungicidal properties which help control powdery mildew on plants and other fungal diseases even on lawns.

Despite the many benefits, I would say use milk really sparingly – it smells as it breaks down, and the fungus that grow on leaves and mulches while breaking the milk down aren’t pretty. Additionally too much milk can cause wilted growth, especially in dry summer climates.

And lastly, only full fat milk works!


Solid Fertilizers:

  • Banana skins

Banana

This one is probably my favourite as it involves so little preparation. Once you have finished eating a banana, tear the peel into smallish pieces and then place onto the soil around a plant. It breaks down into the soil really quickly, encourages a ton of microbial activity and the N-P-K is 0 – 3 – 42.

All that potassium is a godsend for plant vigour and if you use it around fruiting plants after buds have been set you will increase yield and is good to counter some of the effects of June drop in Apples and Pears.

  • Egg shells

eggsMost people swear by crushed egg shells in soil mixes or composts: the N-P-K is approximately 1.0 – 0.4 – 0.1; not especially high, but when egg shells break down they also release calcium carbonate which can counter acidity. However, you would need a lot of egg shells to change soil pH on a permanent basis.

  • Fish

fishA very ancient tradition is to place a small fish in the panting hole of a tree or shrub. American Indians also used fish heads before sowing corn. Not everyone has whole fish to spare,  but any uncooked fish pieces (fins, scales, guts, tails etc) will break down very quickly in the soil and are great for hungry plants like fruit trees and roses. The decomposition encourages substantial microbial activity which benefits the soil. Bury it at least 20cm/6″ to avoid foraging animals!

N-P-K is roughly 6.0 – 4.0 – 0.0. You can substitute for other seafood such as prawns/shrimp, but these have an N-P-K of 2.5 – 10.0 – 0.0, which is more closely aligned to typical commercial bone-meal fertilizers (N-P-K 3.0 – 15.0 – 0.0).

Both fish and shrimp waste takes time to be used by plants, and works best in a neutral to slightly acidic (pH 6.0 – 7.0) soil.


Of course, there are many other home-made fertilizer recipes, but these are ones that I have used. Feel free to share your own!

Happy Gardening 🙂

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40 thoughts on “Homemade Eco-friendly Garden Fertilizers

  1. Good information, Matt, especially with the N-P-K ratios. I’m not good with the science. At the moment I am using worm ‘tea’ and compost and also water with fish waste from my ‘pond’.

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  2. Very good to know. If there’s a few things that I have a lot of, its banana peels, egg shells and fish carcasses. I’ve always figured that they’d make decent compost and fertilizer, but now that I know the NPK ratios I can feel confident enough to experiment with them. Thanks!

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  3. This is fantastic information Matt, some of it I knew but to have it all in one place and explained so well is brilliant. I’m going to translate it to share with my Italian gardening class; they love things they can make but are sometimes not very good with diluting what they make. Thank you for taking the trouble to put all this together.

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    • Thanks Christina – its amazing what weeks of cold, wet weather can do in terms of collating lists 🙂 I was lucky enough to have a teacher who picked our brains and then got us to substantiate all of these gardening ‘folklores’. I’m glad I kept the notes on the values as they come in handy when comparing to modern commercial products

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  4. Excellent post Matt, I make comfrey tea and occasionally a nettle tea too. I wash my camellia leaves with a diluted milk solution. To buy organic tonics especially seaweed is very expensive here. Luckily comfrey is rampant in the lane I live in, so we have a plentiful supply, I cut it too and add into my compost bins.

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    • It’s great to be able to make something very useful from things that would otherwise be landfill. I know what you mean about the seaweed: here a 500ml bottle is $8, which doesn’t last particularly long, especially if you are trying to do a whole garden!

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  5. Superbe blog post, Matt, some is new to me and very interesting, especially the weed tea (plenty of those around!). Comfrey grows wild in our woods and is so pretty that I prefer to admire it there. Not invasive here at all. Enjoy the quieter garden days 🙂

    Liked by 1 person

    • Thanks Annette! You often hear people say, you should use XYZ home remedy instead of the store-bought one; but the problem is that there is no way of comparing its effectiveness, so with the npk numbers I’ve also listed the values for commercial seaweed and bone meal values. I hope it helps some people save a bit of money (and the environment – as well as using things around the house, there is much energy, water and packaging used to make just one small container of anything at a commercial level)

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      • So true, Matt. For example my worms love to eat newspaper and cardboard that I use as ‘blankets’ as much as the kitchen and garden waste. They don’t mind old cotton tea towels and garments that are not suitable for giving to charity either! My fish in turn love to eat worms when I have a population explosion now and then and I use their waste so nothing is wasted.

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      • That is fantastic – it’s amazing what sort of closed circuit you can achieve in even smaller gardens where everything is used up until it becomes soil. It’s perfect recycling…I love it!

        Liked by 1 person

  6. I intend to try some of these; many thanks! Too bad only the full-fat milk works, though — I can only buy 1%. By the way, I had the same problem as you do with the milk going “off”, despite being placed in the coldest part of the fridge. I discovered that by decanting the milk into a glass bottle instead, it stays fresher longer, the glass being noticeably colder than a plastic or waxed container. 🙂

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    • It is a shame about the milk, but skimmed (or 1%, or even half-half) can actually cause plant problems…something to do with the conversion of fat to sugars when the milk is processed. For me 1 carton lasts a long time when I only use it to have 2 cups of coffee each day, but I’ll definitely give the glass decanter a try 🙂

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  7. So glad to see this information, Matt! i am trying to relearn soil amendments, etc. in this very dry climate. It is most disconcerting to find that things don’t rot “properly” here ;P so I am glad to see the info on liquid amendments. btw, can you make any suggestions for safely using horse manure (one product I have an abundance of!). Again, it does not break down in the way I am familiar with from a wetter climate! I don’t want to burn the plants… Thanks 🙂

    Liked by 1 person

    • Thanks Amy – with the manures and little water, you would have to compost them in a bigger heap. Normally a pile of manures and brown/greens 3’x3’x3′ would be considered enough to start a hot compost, but in drier climates, you’ll need to make it at least 3’x6’x6′ to get the same effect (in fact, taller if you can manage it). The other thing that horse manure lacks is nitrogen, and a compost low in nitrogen AND dry will keep microbes away, so either add urea or Nitrogen based fertilizer that you buy from the store and then give the heap some water – if the centre is big enough, even the desert air shouldn’t dry it too much

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  8. That was fun, although the description of a “horrible, stinking swill” is a little off-putting ;). Using weeds as fertilizer is appealing – they ought to make some kind of contribution to the garden. I’ve always heard that planting fish guts is good for the soil and plants but as I can vividly imagine how the raccoons might respond, I think I’ll keep that idea on the back-burner.

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  9. Wow Matt, what a well put together post. Having the NPK ratios in there really puts it in perspective. I’ve heard of some if those teas but many of the recipes are new to me, so very interesting!
    I dump most everything on the compost and am guilty of reaching for liquid chemical fertilizers for laziness sake, but I’m going to give a few of these a wirl this summer. Thanks!

    Liked by 1 person

    • Thanks! home-made ones are a great tonic, especially if you’ve space in the garage/shed to store them. I’ve done tests with home-made vs artificial chemical liquid fertilizers and the latter *always* gives more growth (even out-performing commercial seaweed solution), but the thing with the artificial ones is that they do nothing for the soil and just pollute waterways with chemical run-off 😦

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  10. A great post with some really good ideas. I put comfrey and nettles into water for a tonic but goodness it smells. I use banana skins and tea too. . I use coffee grounds round my hostas and delphiniums; slugs and snails hate it.

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  11. Excellent share. I must get cracking and pinch some comfrey from my daughters place to get started before next growing season. SO many things to do, so little time, and they say that the cooler months are supposed to be quiet! 😉

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  12. Hi Matt, thanks for visiting my (balcony) blog. I’m glad I discovered yours – these tips are great. I might attempt some fish for my roses and try some of the more discrete smelling ones to get some microbial actions in the containers. Bookmarking the pest controls for future reference…
    I also very much enjoyed the autumn foliage photos, I’ll check in again!

    Liked by 1 person

  13. hello Matt I follow your blog but missed this post, I used to have the posts of blogs I follow emailed to me but when I had all the problems with not being able to get online, I stopped the emails as my inbox was getting very full, since being back online I have started using wordpress reader and I have thought I might be missing some posts as it only shows the 5 most recent posts of the blogs I follow,
    thanks for all the hints and tips here, I am just making my first comfrey tea and now know I should be stirring it weekly, I use eggshells, bananas I keep and put under some soil in the planting hole when I plant a new plant, tea and coffee go on the compost, I have so much moss and weed they go in the local authority recycle bin, most of the others I do not have being vegetarian leaning towards vegan, I’ve never noticed molasses in my local shops but then there are lots of things we can’t get on the island, thanks for the N-P-K info, Frances
    p.s. Julie @ gardeningjules told me about your post,

    Liked by 1 person

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