Soil and compost
Understanding the foundation of every successful garden
Soil is the foundation of every successful garden, and yet it is the element most often misunderstood, mis-specified, and mis-treated. Across Kingston, Surbiton, Richmond, Esher, Cobham, and the surrounding areas of Surrey, the majority of disappointing planting outcomes are not failures of plant selection or aftercare but failures of soil understanding and compost specification at the start of a project.
Compost, topsoil, soil conditioner, multi-purpose, peat-free, John Innes, ericaceous – the terminology used across garden centres and landscape suppliers suggests these materials are interchangeable variations on a theme. They are not. Each represents a distinct formulation designed for specific applications, and using the wrong type produces predictable failures regardless of the quality of plants chosen or the care taken in planting them.
This guide brings together the soil and compost knowledge that informs every Flourish Landscaping project, from container plantings and raised beds to lawn establishment and clay soil improvement across Surrey. It sits within our wider garden advice section, alongside our garden styles guide and garden orientation guide.
Why soil and compost specification matters
The Kingston, Surbiton, Esher, and Cobham areas sit on London Clay – a heavy, fertile, moisture-retentive subsoil that determines what plants thrive and what fails across most of the region. Working with clay rather than against it is fundamental to successful gardening here, and that starts with understanding what compost is, what topsoil is, and how they differ from the existing soil already in the ground.
Pure compost in a raised bed settles 100–150mm within 2–3 years as its organic structure collapses. The wrong compost in a container kills plants within 18 months regardless of feeding. Ericaceous plants in standard compost develop chlorosis within a single growing season. Mediterranean planting in unimproved Surrey clay fails through winter waterlogging.
These are predictable failures with predictable solutions. The pages in this guide cover the specification knowledge that prevents them – the practical, evidence-based information about which material to use when, why, and where to source quality products across Surrey.
Soil and compost guides
Below is an introduction to each guide in this section. Each has a dedicated page with detailed specifications, practical applications, and information on how the Flourish team approaches material selection on professional projects across Kingston, Surbiton, Esher, Cobham, Thames Ditton, Twickenham, Richmond, and surrounding areas.
Compost: complete guide
Multi-purpose compost, peat-free compost, John Innes compost, ericaceous compost – the labels on garden centre shelves suggest these are interchangeable. They are not. Each formulation has distinct characteristics and appropriate applications, and using the wrong type produces predictable failures regardless of plant selection or aftercare.
Our complete compost guide explains what each type contains, when to use each formulation, why John Innes outperforms multi-purpose for permanent containers despite the higher cost, why peat-free compost becomes hydrophobic when dry, and why ericaceous plants in standard compost develop chlorosis regardless of feeding. Includes quality indicators to look for and Kingston, Surbiton and Surrey suppliers.
Topsoil: complete guide
Topsoil sounds straightforward – soil from the top layer of ground. In practice, products marketed as topsoil range from premium BS3882-certified material suitable for professional landscaping through to contaminated builder’s excavation waste that damages rather than improves gardens. Understanding the difference matters.
Our topsoil guide covers BS3882 specifications and what they guarantee, the three main grades available (Premium, Economy, Blended), how to test topsoil quality before bulk purchase, how to calculate quantities for raised beds and lawns, why pure topsoil is wrong for raised beds and pure compost is equally wrong, and where to source quality topsoil in Surrey from Bourne Amenity, Bury Hill Landscape Supplies, and Topsoil Direct.
Improving clay soil
London Clay underlies most gardens across Kingston, Surbiton, Esher, and Cobham. It is fertile and moisture-retentive when managed correctly – properties that make it genuinely excellent for many plant communities. Worked badly it becomes compacted, waterlogged in winter, and concrete-hard in summer. The difference is technique, not luck.
Our clay soil improvement guide covers the techniques that transform clay from problem to asset: organic matter incorporation rates and frequencies, the practical limitations of grit and sand additions, when raised beds make sense and when they don’t, no-dig versus traditional cultivation approaches on clay, and the timing that matters for clay improvement work in Surrey’s climate.
Compost vs soil: when to use each
Compost and soil are fundamentally different materials despite often being treated as interchangeable. Soil is 85–95% mineral particles with permanent structure. Compost is 90–98% organic matter that decomposes over 12–24 months. Treating them as equivalent – using compost where soil is required or vice versa – produces the failures that account for a significant proportion of disappointing planting outcomes.
Our compost vs soil guide explains the structural differences that matter, why containers need compost but borders need soil, why pure compost in ground-level planting wastes money while delivering worse results than improved existing soil, and the specific situations where one material works and the other fails.
Compost vs topsoil: differences
The question of whether to fill a raised bed with compost, topsoil, or a mixture is one of the most common in Surrey landscaping – and one most frequently answered wrongly. Pure compost settles dramatically and loses structure within 2–3 years. Pure topsoil lacks the organic matter and fertility for optimal plant performance. The 50:50 blend that professional landscapers specify combines the benefits of both materials.
Our compost vs topsoil guide explains why the blend works, what proportions deliver best long-term performance, how to calculate quantities for different raised bed dimensions, and how to specify materials clearly when ordering from Surrey landscape suppliers.
Soil conditioner vs compost
Soil conditioner and compost look similar in the bag and serve overlapping purposes, but they are distinct products with different applications. Soil conditioner is designed primarily for incorporation into existing soil to improve structure and drainage. Compost is designed primarily as growing medium for containers and seasonal plantings, with soil improvement as secondary use.
Our soil conditioner vs compost guide explains the differences in composition, particle size, nutrient content, and intended use; when each material is the correct choice; and why using compost for soil improvement is expensive overkill while using soil conditioner in containers produces poor results.
How to choose the right material for your project
The right material for a garden project is not a matter of preference but of matching specification to application. Compost is the correct choice for containers, seasonal bedding, and seed sowing. Topsoil is the correct choice for raised beds (mixed with compost), lawn establishment, and levelling where stability matters. Soil conditioner is the correct choice for improving existing borders and annual mulching. Confusing these applications produces predictable failures.
Equally important is understanding what each material cannot do. Pure compost will not perform as raised bed fill long-term – structure collapses, levels drop, and the bed requires rebuilding within 3–4 years. Topsoil will not perform as container medium – drainage is too slow and weight excessive. Soil conditioner alone will not support container planting – insufficient nutrients and inappropriate texture.
The pages in this guide explain the specific applications each material is designed for and the situations where it should not be used. The goal is helping clients make informed material decisions before purchasing, rather than discovering specification mistakes after planting failure has already occurred. Our planning your perfect garden guide and garden costs guide provide additional context on project planning.
How Flourish specifies materials for client projects
Material specification is part of every Flourish Landscaping design and build project, drawing on Craig Davis BSc (Hons) Horticulture’s three decades of experience with material performance across Surrey conditions. For raised beds we specify topsoil mixed 50:50 with compost rather than pure compost – the difference between beds that perform for decades and beds that require rebuilding within 3–4 years. For lawn establishment we specify BS3882 Premium topsoil at 100mm minimum depth – the difference between lawns that thrive and lawns that struggle from the start.
For container plantings we specify John Innes No.3 for permanent specimens rather than multi-purpose compost – the difference between containers that perform for years and containers that fail within 18 months. For clay soil improvement we specify organic matter incorporation rather than topsoil addition – more effective, more economical, and more environmentally sound for typical Surrey conditions.
The process begins with understanding the project requirements and the conditions of the site. From there we assess what materials genuinely deliver the outcomes the client expects, specify the correct products from reliable Surrey suppliers, and install them to the standards that determine long-term performance. You can read more about our garden design and build service and our planting design and installation service.
Book a consultation with Flourish Landscaping to discuss material specification for your garden project.
Frequently asked questions
What is the difference between compost, topsoil, and soil conditioner?
Compost is 90–98% decomposed organic matter, used as growing medium for containers and seasonal plantings. Topsoil is natural soil with 85–95% mineral particles and 3–8% organic matter, used for raised beds, lawns, and levelling. Soil conditioner is composted organic matter designed for incorporation into existing soil to improve structure. These are distinct materials with specific applications, not interchangeable variations.
Should I fill my raised bed with pure compost or topsoil?
Neither. The correct specification is 50:50 topsoil and compost. Topsoil provides permanent mineral structure that prevents settling. Compost provides fertility and improved drainage. Pure compost settles 100–150mm within 2–3 years as structure collapses. Pure topsoil lacks organic matter for optimal performance. The blend combines benefits of both materials and is the standard professional specification.
Why do plants die in containers despite regular feeding?
Compost structure collapse, not nutrient deficiency. As compost decomposes over 12–24 months, pore spaces compress, drainage slows, and aeration deteriorates. Roots suffocate in anaerobic conditions regardless of feeding. Symptoms appear identical to nutrient deficiency but feeding makes no improvement. The solution is repotting into fresh compost with proper structure, or using John Innes formulations that maintain structure for years rather than months.
How do I improve heavy clay soil?
Incorporate substantial organic matter annually. This is the single most effective intervention available. Soil conditioner, garden compost, or well-rotted manure incorporated at one to two barrows per square metre transforms clay structure over 3–5 years. Grit additions help drainage but require massive quantities to be effective. Topsoil addition dilutes clay but doesn’t fundamentally change behaviour. See our improving clay soil guide for detailed technique guidance.
Is peat-free compost as good as peat-based?
Different rather than inferior. Peat-free formulations perform adequately for many applications but require adjusted expectations and management. The critical difference is hydrophobic behaviour when dry – wood fibre-based peat-free becomes very difficult to rewet once completely dried. For seasonal bedding and vegetable growing, peat-free works well. For permanent containers prone to drying or critical plantings, peat-based or John Innes remains more reliable. The environmental case for peat-free is strong.
Where can I buy quality compost and topsoil in Surrey?
For bulk supply, Bourne Amenity, Bury Hill Landscape Supplies, and Topsoil Direct deliver across Surrey with BS3882 certified products. For domestic quantities, Squires Garden Centres (Twickenham, Long Ditton, Shepperton), Hillier Garden Centre (Windlesham), and Notcutts Garden Centre (Bagshot) stock comprehensive ranges. Bulk delivery costs 50–70% less than bagged for orders above 1 cubic metre. Always specify BS3882 grade required when ordering bulk topsoil.
