Organic fertilisers (fertilizers)

17 June 2009
If you planted a tomato into virgin Australian soil (and probably most other virgin soils) and watered it, it might live and produce small tomatoes, but it wouldn't thrive. To get the best from your plants you need to help them along. The old saying of organic farmers world wide is "feed the soil, not the plant" and by this they mean it's best to add old cow, horse, sheep, goat, pig manure, compost or organic matter to improve soil structure and add microbes to the soil, than it is to fertilise plants in unimproved soil. If you're going to be gardening for many years, even sandy and clay soil will improve with these additions, and it's better to garden in soil that's alive and healthy rather than just use the top layer that you add each year.

Once you've improved your soil, and even when you're in the process of doing it, you'll be able to plant up a wide variety of vegetables that will take advantage of your work and result in healthy, organic produce for your table. Fertilising is one of the skills of organic vegetable gardening. It's worthwhile giving this a bit of thought because if you get this right, you'll be looking at abundant crops rather than meagre ones.

One of the good things about organic fertilisers is that many of them can be made in your own backyard, and will therefore cut down the cost of your garden. Garden and kitchen waste can be turned into compost or fed to worms, you can grow comfrey to make a nitrogen-rich tea. Comfrey also breaks down the soil it grows in by sending down a long tap root to mine the minerals contained deep within the soil. Most of those minerals will be in your fertiliser. Aged chicken or animal manure, and manure mixed into compost, make fantastic soil additives and will increase the amount of available nitrogen and microbes in your soil.

Foliar feeding is the fertilising of plants through their leaves. You do it by making or buying a liquid fertiliser to the required strength and, using a watering can, pour the liquid over the plant. Plants can absorb a large amount of their nutrients through their leaves. However, some plants do not like this form of fertilising - tomatoes, pumpkins and zucchini come to mind, but most leafy green vegetables love liquid fertiliser.

When making up a commercial liquid fertiliser, be guided by the instructions on the bottle, but make it weaker than they suggest. A weaker brew, applied more frequently, is a better option. So, for example, if they recommend 1 cap full of fertiliser in 10 litres (quarts) of water, applied every month, make yours ½ cupful in 10 litres and apply it every two weeks. You will get better growth that way.

Leafy greens
Leafy greens usually need to grow fast for better taste. Lettuce, spinach, silverbeet, cabbage etc will do really well if you plant them in rich soil, full of compost, aged animal manures and organic matter, and water them every week or two with a weak compost, worm or comfrey tea, or fish emulsion. So with leafy greens you can give them nitrogen in the soil and a foliar feed over their leaves to keep them growing fast.

Fruiting vegetables - tomatoes, cucumbers, pumpkins etc
They will do better if you plant them in rich soil with an application of sulphate of potash to the planting hole. When you plant the seedling or when the seedling emerges, water it with a solution of seaweed tea, made according to the instructions on the bottle. This is more a plant tonic than a fertiliser and it will help your plants cope with a wide range of conditions as well as help them access the available nutrients in the soil and grow good root systems. Don't give fruiting vegetables too much nitrogen and don't give them foliar fertiliser because they'll grow a lot of leaves but give you no fruit. The line is fine here - you want a good healthy plant capable of supporting strong growth and fruit but you don't want to over do it. So good soil + seaweed + watering around the base of the plants - don't water these plants over their leaves, you'll be inviting trouble if you do.

If you have any worm castings, put some in the planting hole or around the base of the plant later on, and cover it with mulch, or make worm tea. The instructions for doing that is in the link below for home made fertilisers.


If you're hoping to make your own nitrogen fertilisers, I encourage you to get some comfrey root and plant it at the edge of your garden or in a large pot. Comfrey leaves can be used for several purposes in the garden - to make nitrogen fertiliser tea, as a mulch for potatoes and to accelerate decomposition in the compost heap. It's a valuable herb. Many people think it's an invasive plant, and it is in a way but it won't take over your garden. It's a clumping plant and it will stay in the area you give it, but if you decide to remove it, any little piece left behind will reshoot. So make sure you give it a permanent position, or plant in a container.

Organic fertilisers
My home made fertiliser recipes
Growing tomatoes from seed

There are many other nutrients necessary in the garden but the fertilisers above are the main ones and they'll get you started. In a couple of years, when you want to learn more about fertilisers, find a good book about organic fertilising and do some reading. It's an interesting subject. And remember, soil improvement and fertilising are ongoing tasks, just like watering and pruning, and are part of every gardening season.


  1. I loved this post - and your veggies look so beautiful - not only the quality of the produce but the quality of the pictures! Great job and great info.

  2. Great info! thank you. I was just going to take time to research this topic. I desire to to make my own "everything" I can :)

  3. We had to work on our soil when we built!

  4. Hello Rhonda, thanks for this very helpful post. I have had some confusion in this area. All clear now.
    I have had a week away and just catching up on the posts I have missed. They are all clear and informative.I hope my tomatoes look like yours when they are ripe!
    The photos are wonderful and I am sure help drive us on to achieve similar results.
    Thanks again.

  5. Where do you get your comfrey from Rhonda?

  6. I use seaweed or comfrey tea to assist seedlings to cope with transplant shock.

  7. Hi everyone!

    Melissa, I got a root cutting from a friend an another from the herb nursery at Maleny about 10 years ago. Most places that sell herbs should stock comfrey.

  8. LOVE the gardening info Rhonda - many thanks!
    Now time stands still in Scandinavia as we all celebrate Midsummer. Tomorrow is Midsummer Eve. At 1pm our time all over the country, young and old celebrate by dancing round the Maypole and singing traditional songs. Maypole in Swedish is majstång and maj means summer foliage - which is what the Maypoles are decked with. This tradition goes back to heathen times of course and yes, it´s a romantic time of year when the sun hardly goes down over the horizon. Magical almost. Most focus though is on the young generation who learn the words and actions to the summer songs and dances round the Maypole as soon as they can walk. This evening we will take our little grandchildren down to our local celebration site in a handcart. Together with other villagers we will deck the Maypole with all kinds of wild flowers and birch leaves. At 1pm tomorrow the strongest locals will heave the pole into its upright position. Then the fun starts. We are lucky to have this national heritage site so close by. There are red painted farm cottages from 17-1800s. An old windmill too from the same period. This actually works after restoration by a local group of villagers.
    So, I would like to wish you and your family and your readers a VERY HAPPY MIDSUMMER.
    Ramona K

  9. Ramona, I just read your comment out to my sister, who is visiting. We would both like to be there with you on your midsummer eve. I'm sure the night will be one to remember. Happy midsummer!

  10. Thanks for the useful post! I also recently read in Country Living magazine (UK) about comfrey tea for organic gardening. I have some tomato plants in pots this year. No tomatoes yet but a few flowers beginning to appear. I hope to have a good crop like yours.

  11. Those tomatoes look absolutley mouth watering. Would you mind sharing what variety they are?

    Thanks for the inspiration.

  12. Thankyou so much for this post- very informative! those tomatoes look good enough to eat- divine!

  13. Seeing this food growing so beautifully must give you such joy, Rhonda, and of course then eating it, knowing exactly where it has come from.

  14. Suzan, the tomatoes are Moneymaker.

  15. Hi Rhonda
    My nearly 16 year old daughter and I have started a vegetable garden together. I gives us something in common and something to talk about. I was wondering if you could help with a different problem that I have? I have alway baked, mended and made and last year even started making our own bread. I had been using Lowans bread improver but they no longer make it. They told me about a company in Melbourne that sell a bread improver but it doubled the cost by the time I added postage. I live on the northern outskirts of Brisbane (approx 40 mins from you) and was wondering if you know of anywhere that I would be able to purchase it closer to home? I would be very greatful if you could help as my bread is more like a cake at the moment!!LOL

  16. Thank you for this post it is very valuable information. I have a question about tomato plants if you could answer it would be great, My tomato plants seem to get so wild with leaves even though I stake them, are the leaves suppose to be thinned out and would that hurt the fruit production? thanks again.

  17. I was wondering where you get the seaweed tea? I frequently check the fertilizer section of our local garden centers but have not found anything like that. I just sprinkled bone and blood meals and some kelp powder down before replanting my beds last week. Do you think kelp powder would have a similar effect? Thank you.

  18. Rhonda-
    running errands yesterday, I had a Target stop on my list and on the $1 rack they had reusable tote bags. I picked up a couple, as I am slowly building a supply and then spotted some that were brown with green printing and they said DOWN TO EARTH!! Had to trade the pink ones for them! Keep up your mission!! and thanks

  19. Thank you! This was so helpful! I do use fish emulsion as fertilizer but I'm very haphazard about the frequency of application.


  20. Cat, I don't know where you live. If you're in Australia, Seasol or Natrakelp are two very good seaweed products. And yes, kelp powder made into a tea would be fine.

    Karen, the word is spreading! LOL

  21. I'm sorry, forgot to put that, but I'm in Oklahoma, USA. I put the powder down directly so may have messed up there, but I did water thoroughly after with soaker hoses so maybe it will be okay anyway.


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