Best Feed for Tomatoes (UK Guide)

Feeding is the difference between a tomato plant that looks healthy and one that produces heavy crops. Tomatoes are hungry plants, and once they start flowering they quickly use up nutrients in compost and soil.

This guide explains the best feed for tomatoes, when to start feeding, and how to avoid the common feeding mistakes UK gardeners make.

For full cultivation advice, see TOMATOES: HOW TO GROW, BEST VARIETIES, PROBLEMS & EXPERT TIPS (UK GUIDE).

Why Tomatoes Need Feeding

Tomatoes grow quickly and produce large amounts of fruit. This uses huge amounts of nutrients, especially:

• Potassium (for fruiting)
• Phosphorus (for roots and flowers)
• Nitrogen (for leaves — but only early on)

Once flowering begins, most compost alone cannot supply enough nutrients for a full season.

Without feeding, plants may:

• Produce lots of leaves but little fruit
• Drop flowers
• Grow slowly
• Produce small tomatoes

The Most Important Nutrient: Potassium

Potassium is the key nutrient for tomatoes.

It:

• Encourages flowering
• Improves fruit size
• Increases flavour
• Helps ripening

This is why tomato feed is different from general plant fertiliser.

When to Start Feeding Tomatoes

Do not start feeding immediately after planting.

Start feeding when:

• First flowers open
• Or tiny fruits begin forming

Feeding too early causes excessive leafy growth and delays fruiting.

How Often to Feed

Typical UK schedule:

• Early season → once per week
• Peak summer → once or twice per week (containers especially)

Plants in pots and grow bags need more feeding than plants in the ground.

Liquid Feed vs Slow-Release Feed

Liquid Tomato Feed

Best during fruiting stage.

Advantages:

• Fast acting
• Easy to control
• Ideal for containers and greenhouses

Slow-Release Fertiliser

Useful at planting time.

Advantages:

• Gradual nutrient supply
• Good for outdoor beds

Many gardeners use both: slow-release early and liquid feed once fruiting begins.

Feeding Tomatoes in Pots

Container tomatoes rely entirely on you for nutrients.

Important tips:

• Feed regularly once flowering starts
• Never allow compost to dry out before feeding
• Increase feeding as fruit load increases

Underfeeding is one of the main reasons for small harvests.

Feeding Tomatoes in the Ground

Soil-grown plants require less feeding but still benefit from:

• Weekly feeding once fruiting
• Rich compost before planting

Plants in poor soil often show pale leaves and weak growth.

Signs Your Tomatoes Need Feeding

• Pale green leaves
• Poor fruit set
• Small tomatoes
• Flowers falling off

Signs of Overfeeding

Too much fertiliser causes:

• Dark lush foliage
• Few flowers
• Delayed fruiting
• Salt build-up in pots

More feed is not always better — balance is key.

Common Feeding Mistakes

• Feeding too early
• Using lawn fertiliser
• Inconsistent feeding
• Feeding dry compost

Always water before feeding.

Final Thoughts

Tomatoes don’t need constant fertiliser — they need feeding at the right time. Start when flowering begins and keep feeding consistently through summer.

Correct feeding dramatically increases yield and fruit quality.

Return to TOMATOES: HOW TO GROW, BEST VARIETIES, PROBLEMS & EXPERT TIPS (UK GUIDE) for complete tomato guidance.