Ericaceous Plants belong to the family Ericaceae, (the heather family) which contains over 1900 species of plants including rhododendrons and blueberries. Most of these plants grow naturally on moorland and have evolved to perform on nutrient poor acid soils with a pH of 4.5 – 5.5 and are known as 'acid-loving plants'.
In line with UK government advice, Glendoick Gardens Ltd runs a reduced peat-use policy for its nursery stock production. Unlike almost all other UK rhododendron and azalea growers, most of Glendoick's stock is grown in the open ground, requiring almost no peat to be used. Following extensive trials, in Glendoick's open ground production, less than 10% peat is used as a planting medium. The remaining 90% consists of top soil, loam, composted bark and composted conifer needles and chipped trimmings. We estimate that our open-ground rhododendron production is the most peat-friendly in the U.K. At Glendoick Gardens, peat is used mainly in propagation and container production. Most peat used is from renewable sources in Scandinavia and the Baltic states. (see below).
Glendoick still uses peat in propagation and in its container mixes (50% peat) as we believe that Ericaceous plants (which grow naturally on peat) require at least some of it for best results.
In summer 2021, I visited the Ericaeous peat free trials at summer NIAB, near Cambridge. All the peat free composts turned the plants grown in them stunted and yellow. The right hand row of Camellias are the control in peat based compost. All the others are peat free and display severe chlorosis. and was dismayed at the terrible results of all the Ericaceous composts tested.
The composts trialled included Melcourt peat free, Miracle-Grow, Westland, Dalefoot and 2 others.
At present there is no ericaceous peat-free compost which I can recommend for containers. The companies selling them should not be allowed to market them as suitable for acid-loving plants, as they are not fit for purpose.
Many Journalists and interested parties have contacted me to say that these webpages are the only balanced account of the peat debate that is available. All the literature and papers have an agenda: envirnmental (anti) or peat producing (pro) and both sides tend to ignore the counter arguments. As usual the truth seems to be more nuanced and complex than either side are willing to conceed. Feel free to quote and link to these pages.
Glendoick director Kenneth Cox is happy to debate the use of peat in any relevent forum, and in any medium. Contact details are on our home page.
It has a low pH ideal for Ericaceous plants. Indeed most of the world's Ericaceous plants have evolved to grow on and in peat.
Peat's high water and air holding capacities which mean that it can retain and subsequently provide moisture and air to the roots of plants.
It holds added nutrients available for plant growth as required.
It is an easy material to handle.
COIR a favourite... but it has to be shipped half way round the world. It is not clean and can harbour fungal pathogens. Shipping organic matter from Sir Lanka surely makes no ecological sense.
GREEN WASTE the challenge with green waste is consistency. It is impossible to get a formula which remains stable from one batch to another or from year to year. Green waste is often contaminated.
HOME MADE COMPOST is great for the small scale. The pH can be a little high for acid-loving plants
COMPOSTED BARK composted pine or Douglas fir bark is used extensively in the USA for container growing of rhododendrons. Good results have been obtained but as the bark breaks down it takes nitrogen from the medium and over time it composts down to a medium with little structure.
LEAF MOULD the ideal substitute if there was enough available. Beech and oak leafmould is a great acidic medium. It is not easy to obtain and a large volume of leaves rots down to a small amount of leafmould (10-20% of the original volume). The other drawback is that it can contain weed and tree seeds which come up in the pots and garden.
COMPOSTED CONIFER NEEDLES Morley nurseries used to sweep these up from conifer plantations and use in their compost mixed with great success. Not easy to obtain but good.
WOOD WOOL this product helps give structure to compost mixes. Glendoick have successful trialled mixed with this material and it works well with up to 20% of the mix. It is hard to obtain and hard to mix, do only works in commercially mixed batches.
Glendoick Gardens believes that the environmental pressure on reduction of peat use by the horticultural industry is valid in protecting lowland UK peat bogs as few such habitats still exist. The campaign, began in the 1980s by David Bellamy, was successful in protecting many remaining lowland peat habitats. I spoke to David Bellamy shortly before he died, about the way the peat debate has evolved. He was dismayed at the attempts to ban peat use entirely as this was not the purpose of his campaign.
Somehow, the worthwhile protection of these lowland peat bogs has lead, almost completely without justification, to a national campaign casting peat use as 'sinful' or morally wrong. There are several arguments put forward to justify the enforced reduction in use of peat but most of these are dubious at best and often factually inaccurate.
1. The main claim leveled is that peat is a 'non-renewable' like oil.
This is simply not true. If carefully harvested from live peat bogs, peat is a renewable resource and can be classified as a 'slowly renewable biofuel'. This can be clearly demonstrated in countries such as Sweden where peat is grown and harvested rather like tree plantations. Scientists have estimated that the annual growth in peat far exceeds the amount that is extracted each year, so it is in essence a renewable resource if well managed.
In November 2000 the European Parliament amended Article 21 of the Council Directive on the promotion of electricity from renewable energy sources in the international electricity market, adding peat to the list of renewable energy sources.
2. It is claimed is that the world is somehow running short of peat.
Again this is simply not true.
The area from Norway to Siberia is, rather simply put, the world's largest peat bog. Canada's is almost as large. A fraction of 1% of the reserves have probably been extracted. On a global scale peatland is not rare nor threatened, the earth is known to generate around 600 million cubic metres per year but only a maximum 200 million cubic metres is extracted each year. So unlike coal or oil, the amount is increasing year on year. Most of the land where the peat is, has little or no alternative use. Compared to farming, fishing, golf courses, or any other major land-use, peat production which is carefully managed, is a sound, sustainable and 'green' activity.
Looking at Scotland for example, around 50% of the land is peat covered as can be seen on the maps, linked to below.
Map of the deep peat deposits in Scotlandhttp://www.macaulay.ac.uk/explorescotland/soils_bp2.html
And this of heather moorlandhttp://www.macaulay.ac.uk/explorescotland/lcs_sc_hm2.html
3. The threat to rare ecosystems from peat extraction:
UK. lowland peatland habitats are scarce and mostly protected. Most of these were drained long ago for farming and forestry. In the UK upland peatland is not threatened. Peat producers have already agreed not to seek or to extract from areas with a conservation value. Peat Extraction for Horticulture is NOT the main cause of damage to the UK peat lands. In fact, since 1960 only just over 500 hectares have been introduced for peat production whereas 95,000 hectares have been lost to forestry. The peatlands of Great Britain cover an area of some 17 500 km2, most in north and west. Scotland has c. 68%, England 23% and Wales 9%. There are about 1 700 km2 of peatland in Northern Ireland, mostly located in the western half of the province.
In Great Britain, commercialised peat extraction takes place on only some 5400 ha (equivalent to about 0.3% of total peatland). Almost all peat industry output is for the horticultural market; there is however still quite extensive (but unquantified) use of peat as a domestic fuel in the rural parts of Scotland and Northern Ireland.
4. Carbon Sink.
Peat bogs soak up carbon dioxide. So does farmland. It is claimed that is we harvest peat this CO2 will be lost. But in fact this is not the case. Peat lands used for extracting peat can be quite easily restored. Draining the peat bogs can be reversed. The Department of the Environment, Peat Producers Association and many other conservation bodies are all working together to restore the peatlands back to their natural state. The carbon sink impact of peat extraction is negligible if the land is correctly managed. This is simply a matter of legislation.
The effect on peat extraction on global warming is complex.
'Temporal studies of peatlands reveal that they may act as CO2 sinks in some years and sources in others, depending on climate. Emissions of CH4 and N2O are similarly variable in space and time.'
In addition, the production of methane in peat bogs contributes to global warming and at best peat bogs are carbon neutral in terms of climate change. (Implementation of an Emissions Inventory for UK Peatlands Client Department for Business, Energy & Industrial Strategy 2017)
From 'Peatlands and Climate change' Available as a pdf from this link.Peatsociety.
Every time a farmer ploughs a field, CO2 is lost into the atmosphere. This is a consequence of turning soil. All soil. Peat is just one example of this.
The release of carbon dioxide is mostly released when peat is drained and not when it is extracted, so this is the key: it has little to do with peat use in horticulture:'
When peatlands are drained, the peat is no longer conserved. It decomposes, which leads to vigorous releases of carbon dioxide. It is estimated that the total carbon emissions from degraded peatlands currently amount to almost half of the worldwide emissions from land use changes and Forestry (lUlUcF) and to 5% of the total global anthropogenic carbon emissions'
Factbook for UNFCCC policies on peat carbon emissions authors: Alex Kaat, Wetlands International, Hans Joosten, Greifswald University
The UK’s peatlands are estimated to occupy a total area of around 3.0 million hectares (12.2 % of the total UK land area).
Of the UK’s total peat area, approximately 640,000 ha (22%) is estimated to remain in a near-natural condition. This area of near natural bog and fen is believed to be continuing to act as a significant net sink for CO2, of c 1,800 kt CO2 yr-1 . This CO2 sink is however counterbalanced by similar emissions of methane (CH4) when its greater 100-year Global Warming Potential is taken into account making near-natural peatlands close to carbon neutral.
A further 1,213,000 ha (41%) of the UK peat area remains under some form of semi-natural peatland vegetation, affected to varying degrees by human activities including drainage, burn management, and livestock grazing. This has led to drying of the peat, loss of peat-forming species and erosion, converting these areas into net Greenhouse Gas sources. Although the emissions per unit area of modified peatland are relatively low, their great extent makes them significant contributors to overall UK peatland GHG emissions
Arable cropland occupies just 7% of the UK’s peat area, but has the highest GHG emissions per unit area of any land-use, with high rates of both CO2 and N2O emissions as a result of drainage and fertilisation. As a result, cropland is estimated to emit 7,600 kt CO2e yr-1 , 32% of total UK peat GHG emissions.
Industrial peat extraction for horticultural use occupies a comparatively small proportion of the UK’s peat area (4,600 ha).
Since 1990, an estimated 95,000 ha of UK peatland have been subject to some form of active restoration intervention, of which around 70,000 ha has involved some form of re-wetting. These activities have occurred in all of the UK administrations, with the majority having taken place in areas of modified blanket bog. Some re-wetting and restoration to peatland vegetation has also occurred in areas of plantation forest, cropland, grassland and peat extraction. In total, these activities are estimated to have generated an emissions reduction since 1990 of 423 kt CO2e yr-1 .
Future emissions projections to 2050 based on a set of illustrative scenarios suggest that currently legislated peat restoration measures (mainly the phasing out of peat extraction in England) will have limited impact on emissions, but that current levels of ambition on peat restoration in all four UK countries could deliver over 4 Mt CO2e yr-1 of emissions reductions by 2050. A more ambitious restoration scenario, including removal of 50% of forest planted on peat since 1980, could deliver over 8 Mt CO2e yr-1 of emissions abatement. However none of our scenarios incorporated large-scale cessation of drainage-based agriculture on lowland peat, which (as it accounts for 60% of all current emissions) placed effective limits on the degree of emissions abatement that could be achieved.
The anti-peat use lobby seems happy to publish information which is simply not accurate which is then copied, or miscopied by garden writers perpetuating the false information. For example Joe Hashman's otherwise useful book Pocket Guide to the Edible Garden states:
'During the latter part of the 20th century 94% of British peat lands were destroyed by the horticulture industry.' His source for this is a Friends of the Earth claim that ‘less than six per cent of Britain's original lowland raised peat bog habitat remains in a near natural condition’.
The Friends of the Earth statistics refer to lowland peat bogs only. Most peat in the UK is in highland peat bogs. And most of the lowland peat bogs were destroyed by draining them for farmland and forestry and not for horticulture. Joe Hashman has apologised to me for this error. But it wont stop this sort of information being spread around.
Horticulture seems to be unfairly blamed by the anti-peat lobby: The reality is that horticulture accounts for only about 2% of peat use. Highland peat on slopes has limited carbon capture and so could be harvested with little environmental impact.
Most peat is burned for fuel. World-wide it may be that as little as 0.1% of the world's peat is being used in horticulture. For some reason, UK environmentalists are unfairly pinning everything onto horticulture.
No other European Country has taken the steps that the UK Government are advocating. Germany is considering restricting peat use. There is clearly no perceived problem in the rest of Europe using peat for horticulture. I have contacted nursery assocications in Holland, France, Germany, Scandinavia and Italy and currently all are perfectly free to use peat in horticulture. This means that UK producers are going to be unfairly penalised if Dutch and German growers are allowed to carry on using peat in their container production. U.K. Governments dont appear to be proposing the banning of importation of plants grown in peat, which is the only fair way to proceed if they wont allow UK producers to grow in peat.
So why is that the UK alone has a fully fledged anti-peat lobby which has chosen to use all sorts of rather underhand propaganda to further its aims. As has been explained, few of its arguments stand up to scrutiny.
The UN Intergovernmental Panel on Climate Change has changed the classification of peat from a 'fossil fuel' to a 'renewable biomass resource' in recognition that peat can indeed by harvested and cultivated sustainably.
At Glendoick, we believe that limited sustainable peat production for horticulture is fully justifiable and the anti-peat lobby are guilty of exaggeration and misinformation. Particularly in propagation, there is no substitute for peat. And many of the alternatives, such as coir, are have very unsound environmental credentials: this is 3rd world organic matter which should be used by local farmers, not shipped expensively round the world. It really is not sound 'green' sense. It needs to be washed and heat sterlised, both of which have envirnonmental consequences.
Peat free composts are fine for soil amelioration and for growing most plants in the garden. They are less effective for container growing as they tend to decompose in an unpredictable pattern.
The dilemma for the gardener is that peat based composts are significantly better than peat free composts for sowing seeds and potting on young plants. Time after time trials reveal this to be true.
Which reported that composts with at least 50% peat were far better than peat free composts in 2010. Which compost trials
Beechgrove Garden trials in 2010 growing potatoes in containers found poor results with peat free composts compared to composts containing at least 50% peat. (Search the factsheets on their website for the results) Beechgrove Garden
The RHS trials published in January 2011 showed the poor results germinating seedlings and potting on young plants most peat alternatives, including loam, wood fibre and coir particularly for plants with very small seeds.
Peat free composts tend to be inconsistent, unstable and often require the addition of extra food and trace elements and many gardeners have complained to me of the poor results with peat free composts. Coir, often used as a replacement for peat is shipped from Sri Lanka which cannot be good for the environment.
The RHS, National Trust RBG, Kew & Edinburgh and other influential organisations, as well as t.v. presenters such as Monty Don should have a little more courage than simply to jump on this bandwagon. Instead they should appraise themselves of the facts and have the courage to portray both sides of the argument. Rather than condemn peat they should explain the facts and defend the sustainable and sensible of peat. At the moment the only reduction in peat seems to be in sales of bags marked 'peat'. If the bag says 'multipurpose compost' or 'ericaceous compost' it sells as well as ever. Such bags usually contain 40-90% peat.
Many well informed gardeners and writers such as Peter Seabrook and the best selling author Dr Hessayon (author of the 'Expert' series) take a pragmatic view. Dr Hessayon writes: 'dont use peat as for overall soil improvement- it is not efficient and garden compost and manure will do a much better job. However moss peat has a role to play in planting and seed composts where there are no substitutes of equal merit' (The Bedside Book of the Garden)
IPS's van Berckel says demand for growing media will increase by 400% to 59m cu m to 244m cu m by 2050. There is 40m cu m current use, with 7m to 11m tonnes co2 emissions annually.
To replace peat is a "massive challenge" despite 40 years of research. Materials are not available in the right quantities or qualities.
To help Governments and NGOs focus on the "real problems" he says percentage land use for peat extraction is 0.05% of worldwide peatlands, and CO2 emissions from drained peatlands, peat extraction is 0.3%.
Van Berckel, of Griendtsveen AG, the Netherlands, says: "Peat is still the most important constituent of growing media, which is important for food production and climate change mitigation, for instance, by providing tree seedlings for afforestation. Worldwide demand is even increasing. Peat replacement by circular materials is already taking place, but this is often a challenge due to quality and quantity issues. Peat for horticulture is only extracted from 0.05% of all peatlands globally. The industry is committed to the Sustainable Development Goals and responsible management, e.g., via certification."
His conclusions are "we need smart solutions" to meet UN goals, including certification of peat extractions according to RPP rules.
Maureen Kuenen, of Responsibly Produced Peat (RPP), the Netherlands, says: "Responsibly Produced Peat can play an important role during the transition time needed to gradually replace peat in horticultural growing media with qualified and climate friendly materials. As long as peat needs to be used it shall come from responsible sources. RPP certification means that impact on High Conservation Values is prevented, and restoration or other wet after-use is secured. It creates opportunities for large scale restoration and paludiculture."
Bernd Hofer, chair of IPS Commission Peatlands and Environment adds:
"Germany's National Peatland Conservation Strategy aims to reduce annual GHG emissions from peatlands by 5 million CO2 tonnes-equiv. by 2030. Only a small element of this can be achieved by phasing out peat extraction and the horticultural use of peat. In relation to the larger share, the rewetting and restoration of around 150,000 hectares of agricultural and forestry land is a major challenge, if this goal is to be achieved by 2030.
The Government’s Peat Working Group initiated the search for suitable materials and this was recognised by re-naming the group in 2005 as the Horticultural Growing Media Forum (HGMF), whose focus was on delivering the peat reduction targets. Some parts of the industry have made significant progress, with the three large national retailers all achieving 50% peat replacement in their bagged product ranges. Partial dilution is becoming the norm for previously all-peat products and several manufacturers have now invested in wood fibre production plants and/or green composting facilities. Unfortunately in the UK, even with the HGMF in place, conflicts of interests, technical problems, increasing costs, reluctance and apathy have all contributed to slow progress towards achieving the 90% target for 2010.
Mires and Peat, Volume 3 (2008), Article 08, www.mires-and-peat.net ISSN 1819-754X
UK peat greenhouse gas emissions (CO2)
Peat Extraction & harvest 36kg per metric tonne
End of life 543kg
Carbon storage -136kg
Green compost 12-93kg
Wood fibre 56-145kg