Best Organic Fertilisers for Tomatoes in Australia (2026 Guide)

After trialling six blends in our Wollongong test beds, two products stood out for unstoppable growth and fruit set: Ocean Grown Fish Hydrolysate and Nurture All – All-Purpose Craft Blend. Here’s the exact program we now recommend to every backyard grower.

Why Tomatoes Are Hungry Crops

Tomatoes pump out kilos of fruit in a single season. Each truss is basically a nutrient dump, pulling nitrogen for leaf growth, phosphorus for roots and flowers, and calcium to stop blossom-end rot. Unless you replace what’s lost, yields nosedive and fruit quality suffers.

Organic fertilisers work with soil microbes instead of against them, building long-term fertility and flavour. That’s why every product in our Organic Garden Fertiliser Collection is free from synthetic salts.

Fool-Proof Feeding Schedule

Growth Stage

Product & Rate

How It Helps

Seed-sowing & Seedling

5 mL Fish Hydrolysate per L water every 7 days

Amino acids jump-start root enzymes; low-heat processing keeps nutrients in a plant-available form.

Transplant Week

1 Tbsp Nurture All mixed into each planting hole

Balanced N-P-K plus trace minerals buffer transplant shock and boost early flowering signals.

Vegetative Push (Weeks 2-4)

10 mL Fish Hydrolysate per L, soil-drench every 10 days

Nitrogen and peptides drive lush canopy without chemical burn risk.

First Flowers & Fruit-Set

Side-dress ½ cup Nurture All per plant; water in with 15 mL Fish Hydrolysate per L

Phosphorus, calcium and potassium set more trusses and tighten cell walls for crack-free skins.

Heavy Fruit Load

Continue 15 mL Fish Hydrolysate per L every 7 days until final harvest

Keeps micronutrients flowing, improves flavour compounds, and stimulates microbial disease resistance.

Pro tip: Hose-end sprayers make Fish Hydrolysate application a two-minute job—no lugging watering cans.

Troubleshooting Nutrient Issues

Symptom

Likely Cause

Quick Fix

Yellow older leaves

Nitrogen lag

Foliar-spray 5 mL Fish Hydrolysate per L at dusk.

Blossom-end rot spots

Calcium imbalance

Side-dress ¼ cup Nurture All; keep soil evenly moist.

Purpling on leaf undersides

Phosphorus shortage (cool soil)

Drench 20 mL Fish Hydrolysate per L; add organic mulch to warm the root zone.

Sparse flowering

Excess nitrogen

Pause Fish Hydrolysate for one cycle; add ½ cup Nurture All to rebalance N-P-K.

Special Tips for Pots & Grow-Bags

Containers dry out fast and leach nutrients quicker than ground beds.

  • Mix 2 Tbsp Nurture All into every 10 L of potting mix before planting.

  • Feed 10 mL Fish Hydrolysate per L of irrigation water weekly.

  • Top-dress ¼ cup Nurture All every four weeks to recharge the mix.

FAQs

Is Fish Hydrolysate safe for seedlings?
Yes. Because it’s produced at low temperatures, the amino acids stay intact and won’t scorch tender roots.

How often should I fertilise tomatoes in winter?
Cut liquid feeds to fortnightly and keep Nurture All side-dresses light; cool temps slow uptake.

Can I use these products in hydroponics?
Fish Hydrolysate is compatible with most bio-hydro systems. Nurture All is soil-focused but works in coco if top-dressed and watered in.

Do organic fertilisers attract pests?
Not when used at the recommended rates. Any fishy aroma dissipates in minutes once watered in.

Ready to feed your tomatoes?

Explore the full Organic Garden Fertiliser range or grab our Tomato Starter Bundle featuring both Fish Hydrolysate and Nurture All—and watch your vines load up with flavour-packed fruit.

About the Author

Scott Cheney - Dr Greenthumbs
Scott Cheney is the Director and Founder of Dr Greenthumbs, with over a decade of hands-on experience in organic gardening. Growing up in rural NSW, Scott’s passion for unusual plants – from cacti to entheogens – evolved into a full-blown commitment to chemical-free gardening when he bought his first property in Wollongong. For the past 8 years running Dr Greenthumbs, Scott has developed unique, first-to-market products like TurboDirt Water Only soil and 100% dry amendment fertiliser blends. When he’s not testing new mixes, you’ll find him swapping gardening tips like your local mate, not giving the hard sell.