8 natural DIY fertilisers for native Australian gardens

Australian soils are ancient, nutrient-poor and extremely low in phosphorus — and that’s exactly how most native plants like it. Many of our local species have evolved ingenious root systems that extract tiny amounts of nutrients from depleted soils.

This means something most gardeners don’t realise: too much fertiliser can stress, burn or even kill Australian natives. A handful of general-purpose fertiliser or a splash of high-phosphorus feed can cause a native to decline quickly. Our natural instinct is to add more, which only accelerates the damage.

So while natives prefer a “lean diet”, there are a handful of safe, low-risk (and cheap) DIY fertilisers you can make at home that nourish your plants without overloading the soil.

1. Diluted Seaweed Water (Native-Safe Tonic)

One of the only fertilisers universally safe for most natives.

Why it works

Seaweed extracts contain trace minerals and natural growth stimulants but almost no phosphorus, making them suitable for Banksia, Grevillea, Hakea and other sensitive species.

How to make it

1. Collect seaweed (where local laws allow).
2. Rinse thoroughly to remove salt.
3. Soak in a bucket for 2–3 days.
4. Dilute 1:2 (one part seaweed water, two parts fresh water).

Alternatively, use a ready-made seaweed solution from your local hardware store.

How often

Every 3–4 weeks.

2. Leaf-Mould Tea (Forest Floor Extract)

As close as you can get to natural bush soil.

Why it works

Leaf-mould tea feeds the soil’s microbial life rather than adding nutrients. It boosts mycorrhizal fungi, which form mutually beneficial relationships with native plant roots.

How to make it

1. Collect fallen gum, wattle or melaleuca leaves.
2. Soak in a bucket for one week.
3. Strain and water the soil — not the foliage.

Best for

Correa, Acacia, Lomandra, Hardenbergia, Westringia.

3. Crushed Native Leaf Litter (Slow-Release Soil Food)

Not technically a fertiliser — but a powerful soil improver.

Why it works

Native leaf litter breaks down slowly, releasing tiny amounts of nutrients while supporting fungi and improving organic matter.

How to use

1. Gather leaves from eucalyptus, melaleuca, grevillea, acacia or any local native species.
2. Avoid exotic deciduous leaves — they break down too quickly and often add nutrients natives don’t like.
3. Crush lightly if desired.
4. Spread a 2–4 cm layer around the dripline (avoid stems).

4. Compost Tea (Very Weak, Highly Diluted)

Provides beneficial microbes without nutrient overload.

Why it works

Compost tea boosts soil biology and improves water infiltration without raising phosphorus to harmful levels.

How to make it

1. Place a small handful of compost in a bucket.
2. Fill with water and steep for 12–24 hours.
3. Strain through a sieve and dilute 1:10.

Best for

Natives that tolerate slightly richer soils: Lilly Pilly, Dianella, Lomandra.

5. Wood Chip Tea (Tannin-Rich Soil Tonic)

An overlooked DIY mix that mimics natural forest chemistry.

Why it works

Tannins gently condition soil and support fungal networks, giving roots a more natural environment.

How to make it

1. Add untreated hardwood chips to a bucket.
2. Cover with water.
3. Steep 5–7 days.
4. Strain and water soil (avoid foliage).

6. Worm Casting Water (Ultra-Mild Nutrient Boost)

Not worm castings themselves — just a diluted liquid that’s extremely native-safe.

Where to get it

• If you have a worm farm: Use the liquid that drains from the bottom tray.
• If not: Buy worm castings, steep 1–2 handfuls in water overnight, then strain.

Why it works

1. Introduces beneficial microbes
2. Improves soil structure and root health
3. Won’t overload nitrogen or phosphorus
4. Helps stressed or heat-affected natives recover

Dilution

Mix 1 tbsp per 4L water (or dilute until the colour of weak tea).

How to apply

Water the base of the plant every 3–4 weeks during warm weather.

7. Charcoal Dust (Simple Biochar-Style Amendment)

Improves soil health without acting like a fertiliser.

Where to get it

From a fire pit or wood heater: collect the black charcoal pieces before they turn to ash.

Why it works

Charcoal:

1. Creates microscopic pores that store water
2. Provides habitat for fungi and microbes
3. Helps sandy soils retain nutrients
4. Mimics the carbon-rich soils many natives evolved in
5. Reduces nutrient loss after heavy rain

How to use

1. Crush into fine dust or small crumbs.
2. Sprinkle a handful per m² around the dripline.
3. Lightly work into the top 1–2 cm of soil.
4. Water well.

Important

Never use ash. It’s highly alkaline and can damage or kill native plants.

8. Boiled Vegetable Water (The Gentler Cousin to Pasta Water)

A mild option for gardeners looking to reuse kitchen waste.

Why it works

Vegetable water contains low levels of micronutrients and no added salts.

How to use

1. Only use water from plain boiled vegetables (no oil, butter or salt).
2. Dilute 1:1.
3. Apply monthly to potted or in-ground natives.

Related article: Can You Use Pasta Water on Plants? 

Feed Smarter, Not Harder

When it comes to Australian native plants, restraint is key. Their beauty comes from thousands of years of adaptation to harsh soils and climate which means a little goes a very long way.

These DIY fertilisers are simple, cost-effective and help your garden thrive without overwhelming sensitive root systems.

These are also great tasks to do with children, so make sure they're equipped with the right tools. If you’re looking for ways to support your garden through the summer heat, explore our terracotta ollas, premium Krumpholz hand tools and durable gardening accessories — all built to withstand tough Australian conditions.