Lawn Fertiliser Guide: Which Nutrients Do You Really Need?

If your lawn looks dull, patchy, or tired — even after regular mowing and watering — the problem is likely nutrient imbalance. Grass is a living plant that relies on a steady diet of essential nutrients to grow strong, green, and disease-resistant. Without them, it weakens, yellows, and lets moss and weeds take over.

This complete UK lawn fertiliser guide will help you understand what those nutrients do, how to choose the right fertiliser for your soil, and when to feed your lawn for the best results all year round.

What Is Lawn Fertiliser and Why It Matters

Fertiliser is essentially plant food — a blend of key nutrients that fuel healthy growth. Your grass relies on three primary elements: nitrogen (N), phosphorus (P), and potassium (K). Together, these are referred to as NPK, and the numbers you see on a fertiliser bag (like 10-5-5) represent the ratio of each nutrient.

Healthy lawns need all three, but not always in equal amounts. Each season, your lawn’s nutrient needs change. In spring, it needs nitrogen to grow; in autumn, it needs potassium and phosphorus to strengthen before winter. Understanding this balance is the secret to greener, more resilient grass.

The Three Essential Lawn Nutrients (NPK Explained)

Nitrogen (N) – For Leaf Growth and Colour

Nitrogen is the key ingredient for lush, green blades. It fuels photosynthesis, helping grass grow thick and vibrant. Too little nitrogen and your lawn turns pale or yellow. Too much, and it grows fast but becomes weak and prone to disease.
Use nitrogen-rich fertiliser in spring and early summer to kick-start growth.

Phosphorus (P) – For Strong Roots

Phosphorus supports deep root development, essential for healthy lawns that withstand drought and wear. It’s particularly important when establishing new turf or repairing damaged areas. Use fertilisers with moderate phosphorus when seeding or in early growth stages.

Potassium (K) – For Strength and Resilience

Potassium helps your grass resist stress from heat, drought, cold, and disease. It regulates water absorption and strengthens cell walls. Autumn fertilisers are typically high in potassium to prepare your lawn for winter.

Reading Fertiliser Labels

Most lawn feeds list their NPK ratio on the packaging, for example:

• Spring/Summer Feed: 10-5-5 (higher nitrogen for green growth)

• Autumn/Winter Feed: 4-12-8 (lower nitrogen, higher phosphorus and potassium)

A balanced fertiliser might read 7-7-7, but for lawns, seasonal adjustments produce far better results.

Types of Lawn Fertiliser

There’s no one-size-fits-all. Here are the main types available in the UK and when to use them.

1. Granular Fertiliser

These are dry pellets spread across your lawn, either manually or with a spreader. They’re ideal for even feeding over larger areas.
Pros: Easy to apply, long-lasting, great for steady feeding.
Cons: Needs watering after application, slower initial results.

2. Liquid Fertiliser

Applied with a watering can or hose-end sprayer, liquid fertilisers deliver nutrients quickly. They’re ideal for quick greening or small patches.
Pros: Fast results, easy to mix with other treatments.
Cons: Shorter lasting, requires more frequent application.

3. Slow-Release Fertiliser

These controlled-release formulas gradually feed your lawn for up to three months. Perfect for busy gardeners who want consistent results with less maintenance.
Pros: Low risk of scorching, minimal effort, steady growth.
Cons: More expensive upfront, less immediate effect.

4. Organic Fertiliser

Made from natural materials like composted manure, seaweed, or bone meal. Organic options improve soil health and microbial activity long-term.
Pros: Eco-friendly, improves soil structure, safe for pets and children.
Cons: Slower to act, nutrients vary naturally, may have an odour.

When to Fertilise Your Lawn in the UK

Timing is critical for effective feeding. Fertilise too early and nutrients wash away; too late and grass can’t absorb them properly.

Spring (March–May): Growth and Revival

After winter dormancy, your lawn craves nitrogen. Use a high-nitrogen feed to encourage fast, green growth and recovery from frost or moss damage.
Apply once temperatures stay consistently above 8°C and rain is forecast within 48 hours.

Summer (June–August): Maintenance and Protection

In summer, switch to a balanced or low-nitrogen fertiliser with extra potassium. This prevents scorching, improves drought tolerance, and strengthens against heavy use. Avoid feeding during heatwaves — wait for cooler evenings or rain.

Autumn (September–November): Strength and Root Growth

Autumn feeding prepares your lawn for the colder months. Use a low-nitrogen, high-potassium formula to harden the grass and boost root resilience. This reduces winter disease risk and keeps your lawn greener through the cold.

Winter (December–February): Rest and Repair

Avoid applying fertiliser in winter unless it’s a specialist winter tonic. Cold soil limits nutrient uptake and can cause waste or run-off. Focus instead on keeping the lawn clear and planning for spring.

How to Apply Lawn Fertiliser Correctly

Step 1: Mow and Clean Up

Mow your lawn a few days before feeding and remove leaves or debris. Never fertilise right after mowing — wait 2–3 days to avoid stressing the grass.

Step 2: Choose the Right Weather

Ideal conditions are mild temperatures, moist soil, and no frost. Avoid windy or scorching days. Rain shortly after application is beneficial but not heavy downpours.

Step 3: Apply Evenly

Use a handheld or wheeled spreader for granular fertilisers to ensure even coverage. For liquid feeds, apply in steady, overlapping passes. Uneven feeding leads to patchy growth.

Step 4: Water In

Water lightly after applying granular fertiliser. This helps dissolve nutrients and prevents leaf burn. Skip watering for liquid feeds — they’re already diluted.

Step 5: Avoid Overfeeding

Overfeeding is a common mistake. Too much nitrogen causes soft growth, disease, and thatch build-up. Always follow the label’s dosage guidelines.

How to Know Your Lawn Needs Feeding

Your lawn is constantly giving you signals. Here’s what to look for:

• Grass turns pale, yellow, or loses vibrancy

• Growth slows even in warm weather

• Weed and moss patches spread

• Soil looks dry and compacted

• Mowing produces little to no clippings

If your grass looks dull despite watering, it’s likely nutrient-hungry. Regular feeding keeps it dense and naturally resistant to pests and weeds.

Common Fertiliser Mistakes to Avoid

1. Feeding too often – More isn’t better; it can cause excessive growth and thatch.

2. Ignoring watering – Fertiliser needs moisture to activate.

3. Applying in frost or heat – Grass can’t absorb nutrients efficiently in extreme conditions.

4. Using the same formula year-round – Seasonal changes require nutrient adjustments.

5. Uneven application – Creates streaks of light and dark green across the lawn.

Building a Year-Round Lawn Feeding Routine

Here’s a simple feeding schedule tailored for UK lawns:

Following this schedule ensures your lawn stays vibrant and healthy across all seasons.

Why DIY Mixing Rarely Works

Some gardeners try to mix their own fertiliser, but store-bought or subscription blends are far more reliable. Homemade mixes often lack precision, leading to nutrient imbalance or chemical burn. Professionally formulated packs are carefully balanced for seasonal needs and soil conditions, ensuring safe, predictable results.

Eco-Friendly Lawn Feeding

Feeding your lawn doesn’t have to harm the environment. Modern fertilisers are more sustainable than ever — many slow-release or organic options reduce nutrient run-off into waterways. Always follow the recommended rates and water efficiently. You can also compost grass clippings to naturally recycle nutrients back into the soil.

Make Feeding Effortless with The Greener Garden Kit

Keeping track of fertiliser types, ratios, and timings can be confusing — especially if you’re not a gardening expert. That’s why we created The Greener Garden Kit, a simple subscription service that delivers the right lawn care pack for each season straight to your door.

Each pack includes:

• Season-specific fertiliser (balanced for the time of year)

• Grass seed mix for thickening and repair

• Moss and weed treatments

• Simple, step-by-step application guide

With one pack per season, you’ll never have to wonder which fertiliser to use or when to apply it. Everything is timed perfectly for the UK climate.

👉 Explore The Greener Garden Kit and enjoy a lush, green lawn without the guesswork.

Frequently Asked Questions

What happens if I don’t fertilise my lawn?
Your grass will become weak, patchy, and more prone to weeds, moss, and disease. Regular feeding keeps it strong and resilient.

Can I use the same fertiliser for my plants and lawn?
Not recommended. Lawn fertilisers are formulated differently — too much nitrogen can damage delicate garden plants.

Is organic fertiliser better than synthetic?
Both work well. Organic options feed the soil long-term, while synthetic fertilisers provide faster visible results. The best approach combines both.

How long should I wait to mow after feeding?
Wait 4–5 days after applying fertiliser before mowing to allow nutrients to settle into the soil.

Can I fertilise right after rain?
Yes, as long as the soil isn’t waterlogged. Moist soil helps nutrient absorption.

Final Thoughts

The key to a perfect UK lawn isn’t endless mowing — it’s balanced feeding. By understanding what your grass needs at each stage of the year and supplying the right nutrients, you’ll achieve the thick, green lawn you’ve always wanted.

Whether you prefer organic or traditional fertilisers, consistency is what matters most. Feed seasonally, water correctly, and watch your lawn transform.

At The Grass Is Always Greener, we make that process effortless with our Greener Garden Kit, combining fertiliser, seed, and treatments in one easy delivery per season.

Order your Greener Garden Kit today and give your lawn the nutrients it deserves — greener, stronger, and healthier all year round.