Whether you’re growing stunning flowers and an abundance of veg, you want your plants to be healthy and great soil is the foundation to a thriving garden. But, with so many fertilisers and soil improvers available, it can be difficult to know which one your plants actually need.
In this guide, we’ll break down some of the most popular garden fertilisers, what they do, when to use them and which plants benefit most.
What’s the difference between a fertiliser and a soil improver?
Before choosing a product, it helps to understand the difference between fertilisers and soil improvers.
What is a plant fertiliser?
Plant fertilisers provide nutrients that plants need to grow, such as nitrogen, phosphorus and potassium.
Different fertilisers support different stages of growth:
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Nitrogen encourages leafy green growth
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Phosphorus supports root development
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Potassium helps flowers and fruit
What are soil improvers?
Soil improvers focus on improving the structure and health of your soil rather than directly feeding plants.
Soil improvers can help:
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Improve drainage
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Increase water retention
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Add organic matter
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Improve clay or sandy soils
Some products such as chicken manure can act as both a fertiliser and soil improver!
Which soil improvers and fertilisers are best?
All plant fertilisers and soil improvers have different jobs so it’s always worth having a multi-purpose fertiliser handy for all round use. You can then buy more specific fertilisers based on what you’re growing.
Multi-purpose fertiliser
Multi-purpose fertilisers, like Levington Growmore Multi-Purpose Plant Food are a great all-round option for general garden use.
They contain a balanced mix of nutrients and can be used on:
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Flower beds
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Containers
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Vegetables
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Shrubs
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Hanging baskets
Multi-purpose fertilisers are best for:
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General plant health
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New gardeners
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Feeding a wide range of plants
When to use: Usually throughout spring and summer during the growing season.
Chicken manure
Chicken manure pellets are one of the most popular organic fertilisers for gardens. They’re excellent for improving poor soils and feeding hungry plants that love organic matter. Over time, they slowly release feed into the soil while also improving soil structure.
Chicken manure is particularly beneficial for plants like:
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Potatoes
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Brassicas
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Tomatoes
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Roses
It can help improve clay soils, encourage strong growth and boost overall soil fertility.
Chicken manure is best for:
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Vegetable gardens
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Improving poor soil
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Organic gardening
When to use: All year round.
Fish, blood and bone
Fish, blood & bone is a traditional organic fertiliser that provides a balanced mix of nutrients. It encourages strong root growth, healthy foliage and improved flowering.
Fish, blood and bone is best for:
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Trees and shrubs
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Root vegetables
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General garden feeding
When to use: Apply during spring and throughout the growing season.
Sulphate of Potash
Sulphate of potash is high in potassium, making it ideal for encouraging flowers and fruit.
Sulphate of potash is best for:
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Tomatoes
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Peppers
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Fruit trees
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Flowering plants
When to use: Use when plants begin flowering and fruiting.
Sulphate of Ammonia
Sulphate of ammonia is a fast-acting nitrogen fertiliser that promotes lush green leafy growth.
Sulphate of ammonia is best for:
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Leafy vegetables
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Lawns
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Brassicas
Top tip: Avoid overusing it, as too much nitrogen can encourage leaves at the expense of flowers or fruit.
Sulphate of iron
Sulphate of iron is commonly used to treat yellowing lawns and plants caused by iron deficiency. It can also help create more acidic soil conditions (perfect for acid-loving plants like blueberries) and prevent moss.
Sulphate or iron is best for:
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Lawns
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Acid-loving plants
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Treating yellow leaves
When to use: During growing season.
Epsom Salts
Epsom salts contain magnesium, which is essential for healthy green growth. Plants lacking magnesium may develop yellow leaves with green veins, but epsom salts can encourage greener leaves through chlorophyll production and improve flowering.
Epsom salts are best for:
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Tomatoes
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Roses
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Peppers
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Houseplants
When to use: All year round.
Lime
Garden lime is used to reduce soil acidity and raise soil pH. Some plants struggle in acidic soil, so adding lime can improve nutrient availability and plant growth.
However, do not use lime around acid-loving plants such as blueberries, camellias or rhododendrons.
Lime is best used for:
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Vegetable patches
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Brassicas
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Lawns
When to use: During autumn or winter to allow time for it to work into the soil.
Which fertiliser should you choose?
The best fertiliser depends on your soil type, plants and gardening goals.
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For general feeding: multi-purpose fertiliser
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For improving poor soil: chicken manure
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For flowers and fruit: sulphate of potash
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For leafy growth: sulphate of ammonia
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For yellowing leaves: sulphate of iron or Epsom salts
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For acidic soil: garden lime
Understanding what your soil and plants need will help you choose the right product and create healthier, more productive gardens all season long.
Which fertiliser does each plant need?
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What fertiliser does sweetcorn need? – Chicken manure pellets, Fish, Blood & Bone, Sulphate of Ammonia (early growth)
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What fertiliser do cucumbers need? – Chicken manure pellets, Fish, Blood & Bone, Sulphate of Potash (when flowering and fruiting)
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What fertiliser do tomatoes need? – Chicken manure pellets, Fish, Blood & Bone, Sulphate of Potash, Epsom Salts (if magnesium deficient)
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What fertiliser do peppers & chillies need? – Fish, Blood & Bone, Sulphate of Potash, Epsom Salts
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What fertiliser do potatoes need? – Chicken manure pellets, Fish, Blood & Bone, Sulphate of Potash
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What fertiliser do salad crops need? (lettuce, rocket, spinach) – Multi-purpose fertiliser, Fish, Blood & Bone, Sulphate of Ammonia (for leafy growth)
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What fertiliser do strawberries need? – Fish, Blood & Bone, Sulphate of Potash
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What fertiliser do courgettes need?– Chicken manure pellets, Fish, Blood & Bone, Sulphate of Potash
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What fertiliser do pumpkins & squash need? – Chicken manure pellets, Fish, Blood & Bone, Sulphate of Potash
Signs your plants or soil need feeding
Plants and soil often show visible signs when they’re lacking nutrients. But, you shouldn’t just rely on fertilisers to keep your plants healthy as choosing high-quality compost that’s right for your plants is the best starting point.
Check out our compost buying guide for advice on picking the right compost for your plants needs.
There are a few symptoms that you can look out for to help prevent weak growth, poor flowering and disappointing harvests.
Common signs your plants may need feeding:
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Yellowing leaves
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Pale or weak growth
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Smaller flowers or fruit
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Slow growth
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Fewer blooms
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Leaves dropping early
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Poor vegetable harvests
Signs your soil may need improving:
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Water sitting on the surface
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Dry soil that struggles to retain moisture
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Hard, compacted clay soil
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Sandy soil with poor structure
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Plants repeatedly struggling in the same area
Different fertilisers provide different nutrients, so identifying the symptoms can help you choose the right product for your garden.
For example, plants with yellow leaves may indicate a magnesium or nitrogen deficiency whereas weak leafy growth can point to a lack of nitrogen.
Common fertiliser mistakes to avoid
Using the right fertiliser at the wrong time, or in the wrong way, can sometimes do more harm than good. Avoiding these common mistakes can help keep plants healthy and prevent damage.
Overfeeding plants
Too much fertiliser can scorch roots, damage foliage and encourage weak, overly soft growth. Always follow the recommended application rates.
Applying fertiliser to dry soil
Applying fertiliser to very dry soil can stress plants and damage roots. Water the soil first or apply before rainfall where appropriate.
Using the wrong fertiliser at the wrong time
Different plants need different nutrients throughout the year. High-nitrogen feeds encourage leafy growth, while potassium-rich fertilisers are better for flowers and fruit.
Feeding plants during winter dormancy
Most outdoor plants slow down or stop growing during winter, meaning they usually don’t need feeding until spring returns.
Adding lime to acid-loving plants
Plants such as blueberries, camellias, azaleas and rhododendrons prefer acidic soil conditions. Adding lime can raise the soil pH too much and affect plant health.
Applying too close to stems or roots
Some fertilisers, especially stronger products like chicken manure pellets or sulphate of ammonia, should not be placed directly against plant stems or roots.
Forgetting to wear gloves
Some fertilisers can irritate skin, so it’s always best to wear gardening gloves and wash hands after use.
Plant fertiliser FAQs
What is the best fertiliser for plants?
The best fertiliser depends on the type of plant and what it needs. Multi-purpose fertilisers are ideal for general use, while products like sulphate of potash are better for flowering and fruiting plants.
Is chicken manure good for gardens?
Yes, chicken manure is excellent for improving soil and feeding hungry plants. It adds nutrients slowly while also improving soil structure and organic matter.
How often should you fertilise plants?
Most plants benefit from feeding during spring and summer when actively growing. Always follow the instructions on the product packaging, as overfeeding can damage plants.
Can you overfeed plants?
Yes. Too much fertiliser can scorch roots, damage foliage and encourage weak growth. It’s important to apply the correct amount and water plants afterwards where recommended.
What fertiliser helps plants flower?
Fertilisers high in potassium, such as sulphate of potash, help encourage flowers and fruit production.
What’s the difference between compost and fertiliser?
Compost improves soil structure and adds organic matter, while fertilisers provide concentrated nutrients that plants need for growth.
Is fish, blood and bone good for all plants?
Fish, blood & bone is suitable for many plants including vegetables, roses, shrubs and flowers, making it a popular all-purpose organic fertiliser.
What does Epsom salt do for plants?
Epsom salts provide magnesium, which supports healthy green growth and can help correct magnesium deficiencies in plants like tomatoes and roses.
When should you add lime to soil?
Lime is usually added during autumn or winter to reduce soil acidity and improve nutrient availability before the growing season begins.
Which fertiliser is best for vegetables?
Vegetables benefit from different fertilisers depending on the crop. Chicken manure and fish, blood & bone are popular choices for general vegetable growing, while sulphate of potash is often used for tomatoes and peppers.
Choosing the right fertiliser doesn't have to be complicated. While every garden and plant has different needs, understanding what each product does can help you provide the right nutrients at the right time. Now you'll be well equipped to keep your garden thriving throughout the growing season.