Spring is the best time to feed our soil and plants. Using organic soil amendments to improve the soil structure in your garden will help with producing bumper crops in our vegetable and flower gardens through summer.
Written by Elly Keen (@daydream.green)
The 2025 Spring Gardening Series is supported by Gubba Garden Store.
There are many benefits for doing things naturally in the garden. For one, the buildup of synthetic pesticides and fertilisers is bad for our environment. Overuse of fertilisers can run off into waterways and damage the aquatic life. And while spraying pesticides may rid you of bad bugs, it can also wipe out the beneficial ones too.
Synthetic also may result in a bigger crop, but is bigger always better? Fast, supersized growth almost always results in loss of flavour – the best taste comes from organic methods.
Here are some ways to create your own natural fertilisers in the garden for free to keep your crops healthy.
Feeding the soil with amendments
Every year your garden soil will lose about 20% of its organic matter, so adding amendments into the soil annually is a good idea. It helps keep soil healthy because it creates aggregates and improves the structure allowing air and oxygen to move freely through.
Organic matter can be added to the garden by working these nutrient rich materials in:
If you are planting vegetables into a raised bed, you may notice that the levels have dropped. This is your signal to top the beds up with a store-bought vegetable mix (includes high-quality topsoil, compost and controlled release fertilisers).
Finishing the soil with a mulch is a must, to prevent weeds and retain moisture. Pea straw, leaves or decomposed wood chips all make beneficial mulches that add nutrients and microbiology to the soil as they continue to breakdown over time.
Feeding plants with liquid fertilisers
Organic matter feeds the soil, while liquid fertilisers feed the plants.
When you use a liquid fertiliser, it’s like a shot for the plant to encourage it to grow bigger and stronger. During active growth, you can use liquid fertilisers every couple of weeks in the garden.
Liquid fertilisers can be both organic (made from animal or plant material) or inorganic (made from a chemical mixture of minerals). Inorganic fertilisers can be inexpensive and contain a large amount of nutrients that are easily accessed by the plant. The downside is that misuse can lead to plant toxicity or leaching, which is bad for the environment.
There are a range of organic liquid fertilisers that can be used instead which are beneficial to both plant and soil health. You can either purchase concentrated bottles and dilute before adding to the garden or make your own at home.
Store bought:
- Seaweed
- Fish emulsion
- Blood and bone
- Humates
Some good organic products available to buy are: Microbe Pro from SeaCliff Organics and a range of products from EMNZ. Solo sprayers are a great way to apply liquid fertilisers. (All available through Gubba Garden Store).
Homemade:
- Vermicast tea (“worm tea”)
- Bokashi tea
- Manure & compost tea
- Comfrey tea
- Eggshell (calcium) extraction
Homemade fertilisers are usually easy to make and are very inexpensive. Vermicast (aka worm poo) is a product of worm farms which can be soaked in water and applied straight to the garden. Bokashi composting has a similar system where the liquid run off can be used as a powerful plant tonic, jam packed with beneficial microbes when diluted.
Making your own liquid fertilisers
Manure & compost tea
If you have access to animal manure or homemade compost, you can create your own liquid fertiliser by soaking these products in water for a couple of days before applying it to the garden.
These teas will need to be strained through a muslin cloth or fine strainer, or the contents steeped inside a mesh bag. The result is a very gentle tonic that conditions soil as it encourages microbial activity. The key here is to use well-aged compost or manure. (And beware that animal manures can spread weed seeds.)
Fish emulsion & seaweed solution
Close to the beach? You can responsibly collect seaweed from the shores and make your own extract.
The type of seaweed to look for is kelp, which is usually dark brown in colour. Wash off the excess saltwater and chop it into small pieces before steeping in water for a couple of months.
If you are a keen fisher, then fish guts, bones and skin can also be stored and frozen until you have enough to make your own fish emulsion. This brew is particularly stinky though, so you’ll need a bucket with a secure lid and small holes drilled in the top for airflow. Keep well away from the house or inhabited areas for 3 months until it breaks down and the smell lessens.
Comfrey & weed teas
Comfrey is a perennial herb that is widely available at the garden centre. It is one plant every gardener get their hands on because of its magical powers.
You see, comfrey has the ability to pull nutrients deep from within the soil through its long tap root, and stores them within the leaves. Comfrey can then easily be harvested multiple times per year and transformed into a pungent, powerful fertiliser for your garden.
To do this, simply:
1. Harvest comfrey leaves from the plant, leaving the heart so the plant can replenish itself.
2. Take a tub (one that is dark coloured where sunlight cannot penetrate is ideal) and shred up the comfrey leaves with your hands (or scissors). The leaves are hairy and can feel a bit spiky so wear gloves for protection when doing this.
3. Add water until it is just covering the leaves, you can weigh them down with some rocks for the first little while if needed until they begin to break up and decompose.
4. After a month, the liquid will be dark green in colour and have a very stinky smell. The liquid can then be diluted with water in a ratio of 1:10 and applied to the garden fortnightly.
Comfrey is high in the three major nutrients (NPK – nitrogen, phosphorus and potassium) and has high levels of calcium. Therefore, it is beneficial for most crops throughout their growing cycles, boosting leafy growth and encouraging more flowers and fruit.
Comfrey can be seen as an invasive plant as it spreads easily, and its taproot runs so deep it’s almost impossible to dig out fully once established. Therefore, I like to plant my patch of comfrey away from the main garden. Instead, I have planted comfrey next to my compost bins which makes harvesting easier too!
If you do not want to make a tea, comfrey leaves can also be added directly to compost bins to enrich the mix, or laid straight on top of garden beds as a mulch. If you don’t have comfrey in your garden, don’t worry. Weeds like nettle also make a powerful fertiliser.
The Spring Gardening Series is proudly supported by Gubba Garden Store.
www.gubba.co.nz | @gubbagardenstorenz
