Composting and peat-freegardening

www.naturalengland.org.uk

Many gardeners don’t think twice about using peat and can’t imagine usinganything else, so they might be surprised to learn that it is a relative newcomerto the horticultural scene. In fact, peat only started to be used widely in the1950s. Sadly, this led directly to the destruction of some wonderful wildlifehabitats in Britain. While some of our remaining peatlands are now protected,there are many in other European countries that aren't, and it is these that nowsupply most of our garden peat. This leaflet explains the value of wildpeatlands and what will be lost if gardeners continue to use peat. It alsoexplains what alternatives exist and how to use them.

Where does peat come from?Peat forms in waterlogged conditionswhere the lack of oxygen preventsdead plants from decaying fully.Plants such as sphagnum mosses,bog cotton and heathers grow anddie on the bog surface and layers ofthis dead plant material graduallyaccumulate over thousands of years.The weight of the upper layers then

Why is peat important?Peat bogs form some of England’smost scarce habitats and provide aunique home for many native plantsand animals, as well as stopping-offpoints for migrating birds. Peat bogsalso contain a lot of importantscientific information. By extractingcores of peat and examining thedifferent layers, we can tell what ourlandscape used to be like and whattypes of plants and animals livedthere. We can also find out aboutpast weather conditions, helping usto understand current trends such asglobal warming. The loss of peatlandscan also contribute to the globalwarming process; they form animportant ‘carbon sink’, holding morecarbon than all the world’s forests. Aspeatlands degrade, this carbon isreleased into the atmosphere.

Composting and peat-free gardening

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Lowland bogs both here and abroad are being destroyed by peat cutting. Peter Wakely/Natural England

Processing peat. Peter Roworth/Natural England

Uses of peat

slowly compresses the lower ones toform peat. In the UK, peatlands cover1.6 million hectares. Around 95 percent of this area is upland blanketbog, the remainder consisting oflowland raised bog. It is the lowlandbogs that are used for peat extractionand of the 70,000 ha left, less than atenth is in pristine or near naturalcondition.

Humans have used peat for centuriesas a fuel, a building material, foranimal bedding and, more recently,for horticulture. In the UK, gardenersand commercial growers get through3.5 million cubic metres of peat ayear. To meet this demand, areas oflowland bog are being stripped oftheir peat, destroying valuablehabitats both here and abroad (65 percent of our peat is now imported).Because peat bogs take so long toform they are an unsustainableresource. If we continue to destroythese peat habitats we will ruin a vitalpart of our natural heritage, losemany rare plants and animals, andvaluable information about ourplanet’s past.

Peat in the gardenPeat has three uses in the garden:as a mulch, a soil improver and agrowing medium.

MulchesA mulch is a layer of materialspread on top of the soil to keepdown weeds, conserve moistureand insulate the earth. Peat-basedmulches do a relatively poor job asthey break down quickly in dryconditions and often just blow away.Better mulches are based on bark,leaf mould, recycled wood waste,spent mushroom compost orgarden compost.

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Soil improversThese can be used to add organicmatter to the soil, to help break downheavy soils or bind lighter ones.They add nutrients and increase thebiodiversity of soil, encouragingbeneficial organisms such asearthworms. Peat-based soilimprovers can improve soil textureand increase its ability to retain waterbut nearly all peat-free soil improverscan do the job better. Peat-freeimprovers are usually based on woodwaste, spent mushroom compost,garden compost, leaf mould orfarmyard manure.

Growing mediaIn the UK, 96 per cent of horticulturalpeat is used in growing media. Aroundtwo-thirds of this is used by domesticgardeners. Most growing media aregiven the catch-all title of ‘potting

compost’. However, they are rarely‘true’ composts and should perhapsbe referred to as ‘compotes’ – mixturesof materials such as loam, peat, sandand fertiliser. Peat actually makes avery good growing medium as it is abland substance that behaves in apredictable way. It can cope withover- and under-watering, and itsrelatively low pH and uniform nutrientlevels mean that manufacturers canfine-tune their ‘compost’ recipes tomeet different needs. Many peat-freegrowing media are now available tothe domestic gardener. Some peat-freeproducts had a bad press in the pastbut new formulas, materials andmanufacturing techniques haveresulted in growing media that equaland often excel those based on peat.However, their success depends onfollowing the instructions – especiallyfor watering and feeding.G

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A wetland dweller: the purple-bordered gold moth . Roger Key/Natural England

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Coir (coconut fibre)Although we think of this as a ‘new’product it was widely used beforepeat came on the gardening scene. In1951 the RHS Dictionary of Gardeningdescribed coir, stating: ‘There isnothing that can quite take its place, agood peat being the nearest.’ Coir ismost often used as a bulking agent inpeat-free growing media, but it has arelatively high pH so is not suitable forericaceous species and conifers. In thepast, coir was sometimes consideredunreliable due to the presence ofpathogens, or salt-watercontamination that occurred duringtransportation. Today, improvedquality-control has made coir a farmore consistent product. Some plants,such as fuchsias, actually prefer coirto peat. In addition to coir, shreddedcoconut shells are sometimes used asa mulch. A negative aspect of theseproducts is that they are importedfrom Sri Lanka; it’s a long trip that hasan environmental cost.

Composted wasteCompost is very variable incomposition and tends to be quiteacidic, with high nutrient levels.It is most useful as a soil improverbut is increasingly being combinedwith other materials to makegrowing media.

Composted brackenWhen composted at hightemperatures, bracken can be usedas a soil improver or mulch. It is lessuseful as a growing medium as it haspoor water retention. For this reasonbracken-based growing media areusually blended with peat or coir.

Animal manureMixed with straw and compostedfor at least six months, manuremakes a very good soil improverbut is too nutrient-rich to use as agrowing medium without dilution.(See also Composting animalmanure, page 14.)

The traditional compost heap, an asset to any garden. Silvestris Fotoservice/FLPA

Simple plastic compost bins can be very efficient. Wiggly Wigglers

Peat substitutesBark and wood wasteThese by-products of the timberindustry are usually used for mulchingand, when composted, for soilimprovement. Composted wood fibreis sometimes used as a bulking agentin low-peat potting composts.

Spent mushroom compostThis is a mixture of wet straw, chickenlitter, horse manure and gypsumthat is then composted to hightemperatures to sterilise it. It is anexcellent improver for heavy soils butis not used in growing media due to itshigh nutrient content and pH.

BiosolidsThe new name for sewage sludge!Untreated sewage used to beploughed into agricultural landas a soil improver and fertiliser, butdue to the health risk only treatedsewage is now used this way.Standard ‘treated sewage’ has had99 per cent of its bacteria destroyed,while ‘enhanced treated’ sewageincreases this proportion to 99.9999per cent! Enhanced treated sewageis virtually sterile. There’s no reasonit shouldn’t be used in the gardenbut, at present, it is not availableto domestic growers.

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as a sowing compost; a mixture ofequal parts garden compost, soil andleaf mould as a potting compost; anda 50:50 mix of garden compost andsoil as a container compost.

Even if you don’t make gardencompost yourself you can always gethold of some; many local authoritiessell compost made using waste fromdomestic gardens and localgreenspaces.

Heap or bin?The simplest way to compost gardenand kitchen waste is to pile it in aheap and let nature take its course.While this arrangement will suitmany, others might find anunfettered heap an eyesore. Another

An attractive ‘beehive’ composter can be a gardenfeature in its own right. Wiggly Wigglers

There are now many excellent peat-freegrowing media. Fiona O’Mahony/NaturalEngland

Read the label!

Leaf mouldComposted leaves make a good soilconditioner and can be used ingrowing media. Some John Innesrecipes have recommended leafmould as a substitute for peat seealso Making leaf mould, page 17.

Spent hopsThese are a by-product of thebrewing industry. They have littlenutritional value but are useful as asoil conditioner. They are strongsmelling and unsuitable as a mulchor growing medium.

Composted waste has high nutrient levels. Fiona O’Mahony/Natural England

Making compostGarden compost is made fromrecycled kitchen and garden waste.Apart from helping gardeners useless peat, composting also reducesthe amount of land used for rubbishdisposal. Roughly 25 per cent ofdomestic waste consists of foodscraps, and much of it can becomposted rather than going to land-fill (not to mention othercompostable materials such as paperand cardboard). Once made,compost is best used as a soilimprover, dug into the topsoil to addnutrients and introduce organicmatter. Those who prefer not to digcan add compost in the form of amulch spread over the soil surface.Nutrients will leach into the soil asthe compost decomposes and wormswill drag organic matter into theirburrows.

Garden compost can even be used tomake growing media. One recipesuggests a mixture of 2 partscompost, 1 part loam/good soil and 1part leaf mould or coir. A trial byGardening Which? found that a goodgrowing medium could be made bycombining 6 parts garden compost, 1part sand and 1 part ‘John Innes No 1’(itself a combination of 7 parts loam,3 parts peat and 2 parts sand, plusvarious nutrients). Gardening Which?has also recommended leaf mould(or a 50:50 mix of leaf mould and soil)

When buying potting compostsand soil improvers, always readthe label carefully. Some productslabelled ‘green’ or ‘organic’ actuallycontain peat, so look out for thewords ‘peat free’. If you’re buying a‘low peat’ product, find out what‘low’ actually means!

factor is heat – a pile of garden wastewill rot down more quickly if it iswarm, and putting waste in a bin willhelp insulate it.

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Almost any organic matter can be composted as long as it is not meat scraps orcat/dog faeces. The former attract rats, while the latter can transmit diseases tohumans. For best results, everything added to the heap should be chopped-upor shredded as finely as possible. Most organic household waste consists ofgarden waste and kitchen scraps. This can be divided into two groups:the ‘Greens’ and the ‘Browns’.

GreensThese include vegetable peelings,weeds and grass clippings; in fact,any soft vegetation. This materialcontains a lot of water and is high innutrients such as nitrogen.

BrownsThese include woody prunings,stems, tree leaves, cardboard,shredded paper, egg boxes etc. Thismaterial is relatively dry and containslittle nitrogen, but is rich in carbon.

Other things that can be added toyour heap include vacuum cleaner

You can now buy containers specially designed to store compostable kitchen waste. David Williams/Natural England

A simple compost bin can be madewith four wooden stakes. These arestuck in the ground to form a squarewith a base area of 1 x 1 m. Three sidesof this square are then fenced in witha mesh (chicken wire, for example)and the garden and kitchen wastepiled in. Keeping one side openallows easy access for turning ormoving the compost. To conserveheat, the mesh can be lined with oldplastic sacks and the heap coveredwith plastic or old carpet (thoughcarpet with an integral underlayshould not be used as this is oftenimpregnated with insecticides)A cover will also keep out excessrainwater. Ideally, a contained heaplike the one described above ought tohave a volume of at least one cubicmetre as this size will retain heatwithout being too much to handle.A more robust wooden bin like theone illustrated is fairly easy to make ifyou have the tools. Using this design,you make a number of identicalwooden squares from boards (cut to

75 cm lengths), then slot the squarestogether, one on top of another, tomake an open-topped box. Thismeans that the height of the box canbe increased as needed and it can bequickly disassembled to get access tothe compost. Thick boards (2 cm plus)will be easier to screw together thanthin ones and make a strongerstructure, though the corner blocksused to ‘peg’ the squares together willalso provide support.

If you don’t want to make your own,there are many commercial compostbins on the market. These range fromdecorative wooden ‘beehive’ bins toutilitarian plastic containers. Somemore advanced models are on rollersthat allow you to mix the compost bytumbling it. This should be doneevery day to achieve the best results.No clear favourite has emerged fromtesting these designs; it seems thatthe quality of your compost willdepend far more on the ingredientsused than the container.

What to compost

Making a compost bin is a useful DIY project.John Lincoln

Covering your bin will insulate it and keep outexcess rainwater. Wiggly Wigglers

dust, tea bags, coffee grounds andeggshells (though the latter don’t‘compost’ as such). Although it is notrecommended that you add cookedfood scraps to your bin, a few boiledvegetables won’t hurt as long as theyare not mixed with dairy products ormeat. If you have a lot of cookedfood scraps it might be an idea toinstall a kitchen waste-disposal unitthat will grind them up and flushthem into the sewage system.Disposal units reduce the amount offood waste going to land-fill but havean environmental cost in terms ofenergy use.

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The three stages incompost production

Worm stageAfter the bacteria and fungi havedone their work, the heap cools andearthworms and compost worms –also called brandlings or tiger worms– consume what is left, mixing thecompost fragments within their guts.At this stage the compost can beused as a mulch or fertiliser forheavy-feeding plants. Under idealconditions these first two stages canbe completed in two weeks.If compost worms have not yetfound their way to your heap, youmight consider buying some.(See Wormeries, page 16.)

Ripening stageOver six months to a year, a varietyof soil organisms gradually ripenthe compost, breaking it downfurther and sifting it, turning it intoa crumbly fragrant humus.

The compost worm Eisenia fetida, also known as the brandling or tiger worm. Roger Key/Natural England

The key to good composting is to mixgreens and browns in roughly equalproportions. In the first stage of thecomposting process, much of the workis done by bacteria that use thenitrogen in the greens to break downthe carbon in the browns. To do thisefficiently, bacteria need heat,moisture and air.

HeatA healthy compost heap will generatea lot of heat, and covering it, orcontaining it in a compost bin, willhelp trap the warmth. Putting yourheap in a sunny spot will also help,but if it is too exposed it may dry out.

MoistureKeeping your heap or containercovered will allow you to control itsmoisture content, but be careful itdoesn’t get too dry; on the otherhand, if your compost becomeswaterlogged it will be deprived of air.In both cases the composting processwill slow dramatically.

AirIn the initial stages of composting,much of the work is done by ‘aerobic’bacteria (those that need oxygen).Later in the process, worms willbecome important. Both need air tolive. Some commercial compost binshave holes in them for aeration, butthese may be counter-productive andlet out too much heat. An active heapor bin should create its own flow ofair, with the heat it generates risingup and drawing fresh air into thebase. Large heaps have to be turnedregularly to let air into their centres,but you can help a smaller heap bynot compacting the compost andintroducing a small amount of twiggymaterial to help keep its structureopen. If you have a large amount ofcompost to deal with, form it into a‘windrow’. A windrow is an elongatedheap about 1.5 metres tall, 2.5 metreswide, and as long as is necessary.Many gardens will support more than onecompost bin. Anne Brenchley/Natural England

Even some compost bins are compostable. Gardening Which?

In some heaps, the conditions forcomposting are never quite right andthe material breaks down only veryslowly. This is not an ideal state ofaffairs but the heap will eventuallyproduce usable compost. On theother hand, a good heap shouldcompost in three stages:

Heat stageMost of the work is done by fungiand bacteria. They multiply rapidlyand break down organic matter bydigesting it. These oxygen-fuelledmicro-organisms work quickly andgenerate a lot of heat – sometimessufficient to kill weed seeds andpathogens. Compost can start to dryout at this stage, so keep an eye on it.

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What not tocompost:

• meat and fish scraps

• cooked food scraps

• cat and dog faeces

• nappies

• perennial weeds

• ash from coal or coke

• diseased plant material

• glossy or colour-printed paper/cardboard

• synthetic and non-organicmaterials.

Compost bins come in all shapes and sizes. Fiona O‘Mahony/Natural England

It’s often best to compost horse manure separately. Stephen Arnott/Natural England

Dog and cat faeces should not becomposted as both can transmitdiseases to humans (the same appliesto nappies). However, the dung andlitter of herbivorous pets such asgerbils, hamsters and rabbits can beadded to your compost, as canchicken litter.

In all these cases the mixture ofnutrient-rich dung and carbon-richlitter (straw, wood shavings etc) will beof great benefit to your heap.

Manure from larger animals such ashorses can also be added to the heap,but too much might overwhelm it.

Composting animalmanure

Starters/acceleratorsSome compost heaps never seem toget going. In these cases they areeither too wet or too dry or, morelikely, they have a poor nitrogen/carbon (green/brown) balance (seeWhat to compost, page 11). If your

heap consists mainly of kitchenscraps and/or grass clippings, there isprobably too much nitrogen andwater in the mixture. Try turning theheap and adding dry ‘browns’ such asshredded newspaper, cardboard, eggboxes etc. This will add carbon to themix and help break it up and aerate it.

If your heap contains too much dryand woody material, it might needsome help in the form of a ‘compoststarter’ or ‘accelerator’. These can bebought from garden centres andconsist of a mixture of compostingmicro-organisms and nutrients,especially nitrogen. You can makeyour own starter by soaking nettles orcomfrey leaves in rainwater for acouple of weeks and pouring theresulting stew on your heap.Alternatively, you can use dilutedurine. These nitrogen sources willstimulate the composting bacteriaand fungi in your heap..

Large amounts of horse manure arebest composted separately.

Mix it with plenty of straw and coverit to prevent rainwater leaching outtoo many nutrients. Composting cantake a year, but once the manure andstraw is well-rotted it can be added tothe soil as an improver (fresh dungshould not be added to the soil as itshigh nutrient levels can scorch youngplant roots).

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Leaf mould is an excellent mulch andsoil improver and can be used as aningredient in home-made pottingcomposts. The easiest way to makeleaf mould is to collect autumn leavesin a black plastic sack. Water theleaves well, then tie off the sack andpuncture it to make a few small air-holes. Store your sacks in a corner of

Making leaf mould

Leaf mould has many uses and is easy to make. Fiona O’Mahony/Natural England

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Rather than build a heap, you canalso make compost in a trench.Dig a trench approximately 30 cmdeep and backfill it with alternatinglayers of compostable material andsoil. Finish off with a thick layer ofsoil and leave the trench for at leasttwo months. Once the trench hassettled you can use it to grow heavyfeeding plants that will enjoy themoist nutrient-rich conditions.Ideal crops to grow this way includerunner beans, peas, courgettesand pumpkins.

Trench composting

WormeriesWorm composting is different fromtraditional composting as there is noheat-producing bacterial stage. All thework is done by compost wormscalled brandlings Eisenia fetida (alsoknown as tiger worms) and theirrelatives E. hortensis. These worms areavailable from specialist suppliers.Brandlings are found in the wild andwill often colonise a garden compostheap. Since brandlings specialise inliving on rich organic waste and donot live in the soil, how they actuallyfind new heaps is a mystery; perhapsvisiting birds carry brandling eggs ontheir feet. A basic wormery is a plasticbin containing an internal divider offine mesh supported 20 cm or soabove its base. Kitchen waste isdisposed of in the bin and the worms

consume it in the darkness. The endproduct is a nutrient-rich liquid thatdrips into the bottom of the bin. Thisliquid is drained off every so often viaa tap and used as a liquid fertiliser.An advantage of the system is that itis totally enclosed so it is less messythan a traditional compost heap. Itcan also be kept indoors. There aremany commercial wormeries on themarket, or you can make your own.

the garden, and in a year or so theleaves will have broken down into arich humus. Alternatively, make amesh container as described in thesection ‘Heap or bin?’ (page 9) andreserve it specifically for leaves. To accelerate the process, chop upthe leaves beforehand, perhaps byrunning a mower over them. Usingevergreen leaves will result in a mouldideal for use with acid-loving plants.

Some wormeries are quiet sophisticated.

Wiggly Wigglers

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Natural England1 East ParadeSheffield, S1 2ETEnquiry Service: 0845 600 3078enquiries@naturalengland.org.ukwww.naturalengland.org.uk

The Composting Association Tel: 0870160 3270 www.compost.org.uk

Garden Organic (formerly the HDRA) Tel: 024 7630 3517www.gardenorganic.org.uk

Peat-free compost suppliersThe following companies all includepeat-free composts in their productranges: B&Q, Focus, Gem, Homebase,J Arthur Bower’s (now called NewHorizon), Levington and Westland.

The following companies specialisein the manufacture of peat-freegrowing media:

Fertile FibreTel: 01432 853111www.fertilefibre.co.uk

Terra Eco SystemsTel: 0118 964 0301www.terraecosystems.com

Composting equipment suppliersBlackwallTel: 0113 201 8000www.blackwall-ltd.com

Ferndale LodgeTel: 0870 444 1342www.ferndale-lodge.co.uk

Organic Gardening CatalogueTel: 0845 130 1304www.organiccatalog.com

QueenswoodTel: 01568 611 281www.queenswood.co.uk

Two Wests and ElliotTel: 0870 4448274www.twowests.co.uk

Wiggly WigglersTel: 0800 216990www.wigglywigglers.co.uk

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Contacts

Further InformationThis is one of a range of wildlifegardening booklets published byNatural England. For more details,contact the Natural England EnquiryService on 0845 600 3078 or e-mailenquiries@naturalengland.org.uk

Natural England also producesGardening with wildlife in mind anillustrated wildlife reference. Originallyon CD but now also available on-line,Gardening with wildlife in mind hasdetailed information on 800 plants andanimal species often found in ourgardens, and shows how they areecologically linked. Seewww.plantpress.com

Natural England works for people, places and nature toconserve and enhance biodiversity, landscapes andwildlife in rural, urban, coastal and marine areas. Weconserve and enhance the natural environment for itsintrinsic value, the wellbeing and enjoyment of people,and the economic prosperity it brings.

www.naturalengland.org.uk

© Natural England 2007

ISBN 978-1-84754-014-0 Catalogue code NE26

Written by Stephen Arnott. Designed by statusdesign.co.uk

Front cover image: Compost bins. Gardening Which?