Garden compost, well-rotted manure, leaf mould and green manures all improve a UK vegetable bed — but they do different jobs. Here's how to choose between them and when to apply each.
Last updated 4 July 2026
This is about the bulky improvers you dig in or mulch with. For peat-free compost, feeds and consumer products, see our guide to peat-free and eco-friendly products for growing UK vegetables.
Almost every problem I've had on the allotment — poor drainage, crops that sulk, ground that sets like concrete in summer — has traced back to soil that was low on organic matter. The single most reliable thing you can do for a UK vegetable bed is add bulky organic improvers year after year. But "organic matter" isn't one thing, and garden compost, well-rotted manure, leaf mould and green manures each behave differently. This guide compares them so you can choose the right one for your soil and your timing.
Why Bulky Organic Matter Is the Foundation
Bulky improvers do something a bottle of feed can't: they physically change the soil. On heavy clay they open up structure so water drains and roots breathe; on light, sandy soil they act like a sponge, holding on to moisture and nutrients that would otherwise wash straight through. They also feed the soil life — worms and microbes — that keeps a bed healthy over the long term. If you're not sure what you're working with, our guide to the best soil for growing vegetables in the UK helps you identify your soil type first.
A useful rule of thumb: aim to add a layer of bulky organic matter roughly 5cm deep across your beds each year — most often in autumn or winter. On a standard 1.2m × 2.4m raised bed that's around 150 litres, or a good few barrowloads, worked in or left for the worms to pull down.
Garden Compost: The Free Backbone
Home-made garden compost — kitchen scraps, grass clippings, spent plants and cardboard rotted down — is the improver every plot should be making. It's free, it's balanced, and it returns your own garden waste to the soil. It's a good all-rounder for feeding and conditioning beds, though home compost varies in quality and can carry weed seeds if it hasn't heated up properly. Use it as a general soil improver and mulch across most crops.
Well-Rotted Manure: The Heavy Feeder's Choice
Well-rotted animal manure (horse, cow or from bagged sources) is richer than garden compost and brilliant for hungry crops. Two cautions matter in the UK. First, it must be well rotted — at least a year old, dark and crumbly with no ammonia smell; fresh manure scorches roots and robs the soil of nitrogen as it breaks down. Second, only use manure from a source you trust, as residues from certain weedkillers used on pasture can persist and damage sensitive crops like tomatoes, beans and potatoes.
Where manure shines: dig it into beds destined for greedy feeders — brassicas, courgettes, squash, potatoes and the bean trench. It's less suited to root crops like carrots and parsnips, which can fork in freshly manured ground; improve those beds the year before instead.
Leaf Mould: The Slow, Gentle Conditioner
Leaf mould — autumn leaves rotted down for a year or two — is low in nutrients but superb for soil structure and moisture retention, and it's completely free. Rake up fallen leaves, stuff them in a bin bag with a few holes or a wire cage, and leave them. It makes an excellent soil conditioner, a fine mulch, and, once well rotted, part of a home-made seed compost.
Green Manures: Growing Your Own Improver
Green manures (or cover crops) are plants — field beans, phacelia, mustard, grazing rye, clover — sown specifically to be dug back into the soil or cut down as a mulch. They're the improver you grow rather than buy. Sown into empty ground, they protect bare soil over winter, suppress weeds, and add organic matter and, in the case of legumes, nitrogen when turned in before they flower. The Royal Horticultural Society recommends green manures as a practical way to build fertility and protect soil on beds that would otherwise sit empty between crops.
Regional timing note: hardy green manures like field beans and grazing rye are best sown from late summer into autumn to overwinter — sow a little earlier in the colder north and Scotland to let them establish before the cold sets in. Dig them in a few weeks before you need the bed in spring.
Reading the Soil Before You Add
Adding improvers is not a cure for every symptom. Yellowing, stunting or crops that fail despite rich soil can point to a specific deficiency, pH problem or pest rather than a lack of organic matter. Diagnose before you dig — our guide to common UK soil problems and how to fix them covers what the symptoms actually mean. And once you know what to add, the right soil preparation tools make spreading and incorporating it far less of a chore.
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Get the UK Garden Planner →Frequently Asked Questions
What's the difference between garden compost and well-rotted manure?
Garden compost is rotted-down garden and kitchen waste — a balanced, general-purpose soil improver you can make for free. Well-rotted manure is richer in nutrients and better for hungry crops like brassicas and courgettes, but must be aged at least a year and sourced carefully to avoid weedkiller residues. Many growers use compost across the plot and reserve manure for the greediest feeders.
When should I add organic matter to my vegetable beds?
Autumn to winter is the classic time — spread a 5cm layer of compost or well-rotted manure and let the frost and worms work it in over winter, ready for spring sowing. You can also mulch through the growing season. Green manures are sown in the gaps, often late summer into autumn, then dug in before the bed is needed.
Can I put fresh manure straight onto my beds?
No. Fresh manure scorches plant roots and temporarily locks up nitrogen as it rots, starving your crops. It needs to be well rotted — at least a year old, dark, crumbly and without a strong ammonia smell — before it goes on a growing bed. If you only have fresh manure, stack it to rot down first or dig it into an empty bed well ahead of planting.
What is a green manure and do I need one?
A green manure is a crop like field beans, phacelia or grazing rye grown specifically to improve the soil rather than to eat. Sown into empty ground it protects bare soil, suppresses weeds and adds organic matter and nitrogen when dug in. It's especially useful over winter or on any bed that would otherwise sit empty, though it isn't essential if you already mulch heavily with compost or manure.
Is leaf mould worth making if it has few nutrients?
Yes. Leaf mould is low in nutrients but excellent for soil structure and holding moisture, and it costs nothing but fallen leaves and patience. Use it as a soil conditioner, a mulch, or — once well rotted — as an ingredient in home-made seed compost. It complements richer improvers like manure rather than replacing them.
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