What is the best organic fertiliser for tomatoes and vegetables?

The best organic fertiliser for tomatoes and vegetables should provide the nutrients plants need as they grow, flower and produce fruit, while fitting naturally into an organic approach to looking after your soil.

Natural Grower Natural Liquid Fertiliser is a plant-based concentrated feed with an NPK of 3.6-1.5-3.7. It is Approved Organic by the Soil Association, Approved Organic and Biodynamic by the Biodynamic Association, and certified Vegan by the Vegan Society.

Made here in Leicestershire from maize grown on our family farm, it can be used to feed tomatoes and other vegetables as well as fruit, flowers, trees, lawns and houseplants.

How to use it: dilute 100ml (2 capfuls) in 4 litres of water and apply around the base of your plants.

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Why do tomatoes and vegetables need feeding?

Healthy soil is always our starting point at Natural Grower.

For vegetables growing in the ground, adding organic matter and caring for the soil can provide much of the nutrition plants need. But some crops are particularly hungry, and plants growing in pots and containers have access to a much smaller reserve of nutrients.

The RHS advises that fertilisers are particularly useful for plants in pots, fruit and vegetables, while organic gardening should also focus on feeding and maintaining the soil. RHS

Tomatoes, cucumbers, courgettes and other productive crops put a lot of energy into growing, flowering and producing fruit.

As the nutrients available in their compost become depleted, additional feeding can help support continued healthy growth and cropping.

The important thing is not simply to feed more.

It's to feed appropriately, when the plant needs it, and always follow the recommended dilution rate.

What does NPK mean in tomato fertiliser?

You'll see three numbers on most fertilisers. These represent the proportions of the three main plant nutrients: nitrogen (N), phosphorus (P) and potassium (K).

Natural Liquid Fertiliser has an NPK of 3.6-1.5-3.7.

In simple terms:

• Nitrogen (N) supports leafy, vegetative growth
• Phosphorus (P) is important for healthy root and shoot development
• Potassium (K) supports flowering, fruiting and general plant health

Tomatoes and other fruiting plants have a particular need for potassium as they flower and develop fruit. The RHS describes NPK as a useful guide to what a fertiliser provides and notes the importance of potassium for flowering and fruiting. RHS

But plants need more than N, P and K alone, which is why looking after the soil remains an important part of how we grow.

What makes Natural Grower Liquid Fertiliser different?

Plant-based

Natural Liquid Fertiliser is made from maize rather than animal-derived ingredients.

Approved for organic growing

It is Approved Organic by the Soil Association and Approved Organic and Biodynamic by the Biodynamic Association.

Vegan Society certified

Our liquid fertiliser contains no animal-derived ingredients and is independently certified by the Vegan Society.

Made on our farm in Leicestershire

The feed originates from maize grown here on our family farm and forms part of the circular story behind Natural Grower.

One feed for much of the garden

Natural Liquid Fertiliser isn't just for tomatoes. It can be used for vegetables, fruit, flowers, trees, lawns and many houseplants, making it a useful all-round feed through the growing season.

How much Natural Liquid Fertiliser should I use?

Dilute:

100ml of Natural Liquid Fertiliser in 4 litres of water.

That's approximately 2 capfuls per 4-litre watering can.

Apply the diluted feed to the soil or compost around the base of your plants.

For outdoor plants, feed once a week during the growing season.

When fruit is swelling or flower buds are developing, this can be increased to twice a week.

Houseplants can generally be fed every two weeks during active growth.

Always use the recommended dilution. More fertiliser doesn't necessarily mean better results — overfeeding can damage plants and excess nutrients can be lost into the environment. RHS

When should I start feeding tomatoes?

Tomatoes don't need heavy feeding from the moment they're planted.

Give young plants time to establish first.

Once plants are actively growing, Natural Liquid Fertiliser can be used weekly according to the product instructions. As flowering develops and fruits begin to swell, feeding can be increased to twice weekly.

For tomatoes growing in containers or reusable growbags, regular feeding is particularly important because the amount of available compost — and therefore the nutrient reserve — is limited.

The RHS similarly recommends regular liquid feeding for fruit and vegetables grown in containers during the growing season. RHS

A Natural Grower approach to growing tomatoes

For us, successful tomato growing isn't about one bottle of feed. It starts with creating a healthy growing environment.

1. Start with good compost

Plant tomatoes into Natural Compost, either in pots, containers or reusable growbags.

2. Add slow-release nutrition if required

Natural Plant Feed & Soil Improver can be incorporated when planting or used around plants as a nutritious mulch.

As well as providing nutrients, it adds organic matter — an important part of maintaining healthy soil.

3. Feed as plants grow

Once tomatoes are established and growing strongly, begin feeding with diluted Natural Liquid Fertiliser.

4. Increase feeding as fruits develop

When flowers are developing and fruit begins to swell, increase feeding in accordance with the product directions.

And don't forget water. Tomatoes growing in pots need consistent watering as well as feeding.

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Liquid fertiliser or slow-release plant feed — which should I use?

They do slightly different jobs.

Natural Liquid Fertiliser provides nutrients in liquid form and is particularly useful for actively growing plants and vegetables in pots, containers and growbags.

Natural Plant Feed & Soil Improver provides slower-release nutrition while also adding organic matter to the soil.

For a tomato growing in a container, you might therefore use Plant Feed & Soil Improver when planting and Natural Liquid Fertiliser during the growing and fruiting season.

For vegetable beds, our preference is always to think about the soil as well as the plant.

Organic matter supports soil structure and soil organisms, while fertiliser can provide additional nutrients when demanding crops need them. That's also consistent with RHS organic-growing guidance, which puts maintaining fertile soil at the heart of organic gardening. RHS

Can I use Natural Liquid Fertiliser on vegetables other than tomatoes?

Yes.

Natural Liquid Fertiliser is a multipurpose feed and can be used on a wide range of actively growing plants.

These include:

Cucumbers and courgettes — productive plants that can benefit from regular feeding.

Chillies and peppers — particularly as plants begin flowering and fruiting.

Vegetables grown in containers — where the available nutrient reserve is limited.

Soft fruit — where additional feeding is appropriate.

Flowers and flowering containers — to support growth and flowering.

Houseplants — generally feed every two weeks while plants are actively growing.

Individual plants have different nutritional requirements, so always take their particular growing needs into account.

Should I use fertiliser if my soil is already healthy?

Not necessarily.

This is an important part of the Natural Grower philosophy.

Plants growing in healthy garden soil with plenty of organic matter may not need routine additional feeding. The RHS similarly advises that many plants growing in garden soil don't require regular fertiliser and recommends keeping fertiliser use to the amount actually needed. RHS

That's very different from plants growing in containers or hungry crops producing large harvests.

Our approach is therefore:

look after your soil first, then give plants additional nutrition when they need it.

Frequently asked questions

Is Natural Grower Liquid Fertiliser suitable for tomatoes?
Yes. Natural Liquid Fertiliser can be used throughout the active growing season on tomatoes, including plants grown in pots and reusable growbags.

How much Natural Grower Liquid Fertiliser should I use?
Dilute 100ml, or approximately 2 capfuls, in 4 litres of water and apply around the base of plants.

How often should I feed tomatoes?
Feed outdoor plants weekly during active growth. When flowers are developing or fruits are swelling, Natural Liquid Fertiliser can be applied up to twice weekly according to the product instructions.

Is Natural Grower Liquid Fertiliser organic?
Natural Liquid Fertiliser is Approved Organic by the Soil Association and Approved Organic and Biodynamic by the Biodynamic Association. It is also Vegan Society certified.

Is Natural Grower Liquid Fertiliser plant-based?
Yes. It is made from maize grown on our family farm in Leicestershire.

Can I use it on other vegetables?
Yes. Natural Liquid Fertiliser is a multipurpose feed suitable for a wide range of vegetables, fruit, flowers and other actively growing plants.

Can I use Natural Liquid Fertiliser on houseplants?
Yes. It can be used on many houseplants. During active growth, feed approximately every two weeks according to the product instructions.

Do I need both liquid fertiliser and Plant Feed & Soil Improver?
Not necessarily. They perform different roles. Natural Liquid Fertiliser provides regular liquid feeding, while Natural Plant Feed & Soil Improver supplies slower-release nutrition and adds organic matter to the soil. They can also be used together as part of an organic growing programme.

Feed your plants — and look after your soil

A productive vegetable garden isn't created by fertiliser alone.

Start with healthy soil, add organic matter, water consistently and provide additional nutrients when hungry plants need them.

That's the Natural Grower way.

Love your soil. Nurture your plants. Grow organically.

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Last updated: September 2026