Best Fertiliser for Tomatoes – A Complete Grower’s Guide (Australia)

Grow Healthier, Tastier Tomatoes by Understanding What They Need

Tomatoes are among the most rewarding plants to grow, whether you’re tending a home garden, running a greenhouse, or managing a commercial plot. However, achieving a heavy yield of firm, juicy, and flavourful fruit requires more than just sun and water. Tomatoes are considered “heavy feeders,” which means they draw a large amount of nutrients from the growing medium and require a well-balanced, crop-specific fertiliser strategy.

In this guide, we’ll take a deep dive into how to grow tomatoes successfully and how to feed them properly using CompleteGrow’s professional-grade fertilisers. Whether you’re growing in soil, raised beds, or hydroponic systems, this article is tailored for Australian conditions and modern growers.

Getting Started: Tomato Growing Basics

Before applying fertiliser, it’s essential to set up your tomato plants for success. Choose a sunny location—tomatoes need at least 6 to 8 hours of direct sunlight per day. The growing medium should be well-draining, rich in organic matter, and slightly acidic to neutral in pH (around 6.0–6.8).

Start your tomatoes from seed indoors or purchase healthy seedlings from a reputable nursery. Harden off young plants before transplanting them outdoors by gradually exposing them to full sun over 7–10 days.

Key factors that influence fertiliser needs:

• Soil vs. hydroponics – nutrient delivery differs across systems
• Growth stage – seedlings, vegetative, flowering, and fruiting phases all have unique needs
• Temperature and watering – high heat and frequent watering may leach nutrients more rapidly

Understanding Tomato Nutritional Requirements

Tomatoes require a full spectrum of macro and micronutrients throughout their lifecycle. A well-balanced feeding program supports strong roots, lush foliage, abundant flowering, and high-quality fruit set.

Essential nutrients for tomatoes include:

• Nitrogen (N): Promotes leafy, green growth—especially important in early vegetative stages.
• Phosphorus (P): Encourages strong root development and flowering. Critical during transition to fruiting.
• Potassium (K): Improves fruit quality, sugar production, and overall plant strength.
• Calcium (Ca): Prevents blossom-end rot and strengthens cell walls in developing fruit.
• Magnesium (Mg): Supports photosynthesis and chlorophyll production.
• Micronutrients: Trace elements like iron, manganese, boron, and zinc are also vital, especially in soilless systems.

Recommended Product: CompleteGrow NPK 4-18-38 + Calcium & Magnesium

Our CompleteGrow NPK 4-18-38 + CaMg formula is designed specifically for fruiting crops like tomatoes. This is a premium-grade, water-soluble fertiliser used by commercial growers and now available for home gardeners.

Why this formulation is ideal for tomatoes:

• High phosphorus and potassium to stimulate flowering and maximise fruit development
• Includes calcium nitrate to prevent blossom-end rot, a common tomato issue
• Magnesium sulphate ensures proper nutrient transport and vivid foliage colour
• Fully water-soluble and compatible with both hydroponic and soil-based systems
• Buffered pH for optimal uptake (works well between pH 5.5–6.5)

This advanced fertiliser is suitable for:

• Hydroponic growers using DWC, NFT, or drip irrigation systems
• Outdoor gardeners feeding tomatoes in beds or containers
• Greenhouse or polytunnel growers managing environmental variables

Feeding Schedule: When and How to Fertilise Tomatoes

To get the best results, adjust your feeding schedule based on the tomato plant’s life stage:

1. Seedling Stage (Weeks 1–3):

• Use a diluted solution (1/4 strength) of a balanced NPK like 20-20-20
• Apply once per week to avoid burning young roots

2. Vegetative Stage (Weeks 3–6):

• Switch to a 1:1:1 or 3:1:2 ratio fertiliser to support leafy growth
• Apply every 5–7 days with regular watering

3. Flowering & Fruiting Stage (Week 6 onwards):

• Begin applying CompleteGrow NPK 4-18-38 + CaMg
• Feed weekly using EC 2.0–2.2 in hydroponics or standard dilution for soil systems
• Monitor plants for signs of deficiency or excess (e.g., leaf curl, yellowing, fruit deformities)

Always adjust the strength of your solution based on plant response and environmental conditions. Overfeeding can lead to salt buildup or nutrient lockout, especially in containers.

Tips for Growing Better Tomatoes

• Sunlight: Ensure full sun exposure for at least 6 hours daily
• Watering: Keep soil consistently moist, but avoid soggy conditions. Use mulch to retain moisture.
• Staking & Pruning: Train your plants with cages or stakes. Prune side shoots to focus energy on fruiting.
• Crop Rotation: Avoid planting tomatoes in the same spot each year to reduce disease risk
• Soil Testing: Test pH and nutrient levels to guide accurate fertiliser applications

Why Choose CompleteGrow Fertilisers?

CompleteGrow specialises in professional-grade plant nutrition made for Australian conditions. Our tomato-specific fertilisers are:

• Scientifically formulated for each stage of growth
• Free from fillers and low-grade materials
• Available in liquid and powder forms
• Trusted by commercial growers and hobbyists alike

Want better tomatoes this season? Explore CompleteGrow’s Tomato Fertiliser Range