How can you successfully phase out peat in your hobby garden?
The HOT model and demonstration project (“Horticulture with peat-reduced and peat-free substrates based on Renewable Resources”) centres on this question. Weihenstephan-Triesdorf University of Applied Sciences (HSWT), in cooperation with the Nürtingen-Geislingen University of Applied Sciences for Business and the Environment (HfWU), GreenSurvey GmbH and Erfurt University of Applied Sciences, has been developing recommendations for amateur gardeners, the growing media industry and retailers since April 2022.
When the potting compost suddenly seems different
A warm spring day. On the balcony stands a freshly planted window box filled with annual balcony flowers. The leaves still look delicate, a little uncertain – as if they first need to get used to their new surroundings. “Something’s not quite right,” says the keen gardener, running her fingers through the potting compost. It feels coarser, more fibrous, with a richer texture. Different from usual. No wonder – after all, the bag from the garden centre has been labelled “peat-free” since this year.
What might sound like a minor detail at first actually marks a major shift – for millions of amateur gardeners, for potting compost manufacturers and for retailers. For the move away from peat heralds a new era in gardening.
The silent climate protector on our doorstep
Peat is an unassuming substance – dark, light, seemingly unspectacular. And yet it holds enormous potential to influence the climate. Bogs, where peat has formed over many centuries, are effective carbon sinks. When these peatlands are drained to extract peat, CO₂ is released into the atmosphere. In Germany, since the 1980s, peat has no longer been extracted from peatlands but from land previously used for agriculture and/or forestry.
This is precisely where the Federal Ministry of Agriculture, Food and Home Affairs’ (BMLEH) 2022 peat reduction strategy comes in: by 2030, commercial horticulture is to largely phase out the use of peat, whilst in the hobby sector this should be fully achieved by as early as 2026. An ambitious target – and one that is putting the sector under considerable pressure.
Meanwhile, after more than four years of research and an ongoing follow-up project, the sector is no longer quite so far from its target: in 2025, only 33 per cent of potting compost in the consumer sector consisted of peat. This is significantly less than the 55 per cent recorded in 2019, but still a long way from the finish line. However, the proportion of substitutes is steadily increasing, as shown by the figures from IVG (Industrieverband Garten e. V.) and GGS (Gütegemeinschaft Substrate für Pflanzen e. V.) for 2025: green waste compost (36 per cent), wood fibres (17 per cent), bark humus (6 per cent) and coconut-based products (2 per cent).
Peat has spoilt users
But as promising as these figures may sound, they only tell half the story: “Peat is an almost perfect raw material,” says a project team member from the HOT model and demonstration project. “It retains water exceptionally well, is low in nutrients and therefore good to manage – in a way, it has spoilt us.” And that is precisely the problem: no substitute can replicate these properties exactly. Every mixture behaves differently – chemically, physically and biologically. For researchers, this is an exciting challenge. For amateur gardeners, it is often a source of uncertainty.
The HOT project has shown time and again that many people underestimate the importance of peat – or simply know too little about its origin and its impact on the climate. “There is a lack of awareness,” is one of the project’s key findings. “And without understanding, there can be little acceptance.”
New tips for good growth in your garden
The plants are growing, but they need more attention. That’s because peat-free gardening follows new rules:
Fertilisation is changing fundamentally
Green waste compost already contains plenty of nutrients, particularly phosphorus and potassium. Anyone who fertilises ‘as before’ risks over-fertilisation. At the same time, there may be a lack of nitrogen, especially in substrates containing wood fibres. Micro-organisms bind it so quickly that plants cannot absorb it. The result: pale leaves and stunted growth. “You need to react quickly,” say the project team. Re-fertilise with nitrogen – and do so in a targeted manner.
Watering presents a new challenge
Peat stores water like a sponge. Many substitutes cannot do this. The soil dries out more quickly. This means watering more often, but in smaller quantities. A seemingly minor detail with a major impact. Until now, fertilising was often linked to watering: adding liquid fertiliser to the water once a week. But when less water is absorbed, the amount of fertiliser automatically decreases. The researchers therefore recommend separating fertilisation from watering and applying nutrients specifically to each plant, regardless of the watering schedule.
Challenges for the growing media industry and retailers
Whilst amateur gardeners will need to adapt, the growing media industry must address the crucial question: where can sufficient high-quality raw materials be sourced? Green waste compost is in particularly high demand. However, not all compost is suitable. Only single-source green waste with a sufficient proportion of woody material delivers the required quality. Compost made from organic waste is often too high in salt and nutrients, and immature compost can cause damage – a nightmare for manufacturers and customers alike.
Retailers must pay particular attention to storage. In spring, pallets of potting compost pile up outside garden centres and DIY stores, often in the open air. Rain soaks the bags, making them heavy and, in some cases, unwieldy. Inside the sacks, a lack of oxygen and a loss of quality can occur. According to the researchers, there is still much room for improvement in this area.
Amateur horticulture using peat-reduced and peat-free growing media based on Renewable Resources (HOT)
In this project, which is funded by the BMLEH, researchers from Weihenstephan-Triesdorf University of Applied Sciences, Nürtingen-Geislingen University of Applied Sciences for Business and the Environment, the GreenSurvey market research institute and Erfurt University of Applied Sciences are working together to ensure that the transition to peat-free growing media is a success for amateur gardeners.
In HOT1 (sub-project: Demonstration Projects and Specialist Information / sub-project: Marketing Recommendations), the study focused on decision-making processes and factors influencing amateur gardeners’ choice of potting compost. Gaps in knowledge regarding the use of peat-reduced or peat-free potting soils were identified, and appropriate training materials were produced to address these.
In the follow-up project HOT2 (sub-project: Success with peat-free potting soils & practical knowledge for amateur gardeners / sub-project: Use of peat-free potting soils – everyday practices of amateur gardeners), individual research questions are revisited, explored in greater depth and supplemented with additional aspects.
Firstly, further empirical research is being conducted to gain a better understanding of amateur gardeners and their behaviour when purchasing and using potting soils: For example, this year the Chair of Marketing and Management of Renewable Resources is using qualitative interviews in real-world laboratories to investigate how amateur gardeners care for plants without assistance or support, where they obtain information, where and how they shop, and their fundamental attitudes towards peat reduction and sustainability. In 2027, the communication and information materials developed as part of the HOT1 project will then be assessed – again using qualitative interviews – in terms of their applicability and practicality.
Another focus is on concepts and measures to further disseminate the findings to the general public. To this end, targeted formats will be developed for multipliers at the manufacturing, retail and advisory levels, designed to train them to raise awareness of peat-free gardening among various target groups and to support them in the use of peat-free growing media.
Real-world laboratory involving members of the public provides insights into practical applications
In a real-world laboratory, academia and practitioners work closely together. Through this experimental approach, research findings were derived directly from real-world applications. As an integral part of the research process, members of the public make a significant contribution to the acquisition of knowledge through their involvement. In this pilot and demonstration project, a number of amateur gardeners took part over a three-year period. They were given plants in various peat-reduced and peat-free potting soils and kept a diary recording when and how much they watered the plants, how often they fertilised them, and how the plants were thriving.
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As part of the three-year ‘real-world laboratories’ project, participants had two colourfully planted balcony boxes and two pots containing a cocktail tomato delivered to their homes. © HSWT -
The participants kept a diary recording when and how much they watered the plants, how often they fertilised them, and how the plants were thriving. © HSWT
Findings from the use of real-world laboratories
The real-world laboratories and demonstration plantings demonstrate impressively that peat-reduced and peat-free growing media consistently enable successful crop production, provided that fertilisation and irrigation are consistently adjusted. Substrate-specific management proved to be a key factor for success. Nutrient supply, in particular, benefited from nitrogen-rich fertilisers and a simplified, volume-based dosage per planter. This approach significantly reduced application errors and led to more consistent nutrient levels than traditional, irrigation-water-based recommendations.
At the same time, it became clear that peat-free substrates, due to their lower water-holding capacity, need to be watered more frequently, albeit in smaller quantities. Technical aids such as water-retention boxes can reduce the amount of maintenance required, but they only partially compensate for the physical differences and pose risks in the event of prolonged wet conditions. Additives such as superabsorbents or wetting agents, on the other hand, showed hardly any practical benefits.
Overall, the real-world laboratories demonstrate that the transition to peat-free systems is horticulturally feasible – but requires knowledge transfer, clear application recommendations and a significant improvement in product quality.
Knowledge transfer to the general public, the substrate industry and the retail sector
The phase-out of peat is more than just a technical transition. It is a cultural shift. Amateur gardeners will have to adapt their practices. Industry and the retail sector must develop new standards. And we must all learn together to cope with uncertainty.
The HOT project addresses precisely this issue and has developed a wide range of information and training materials for this purpose:
- an online course entitled ‘Peat-Free Gardening’ with background information on the phase-out of peat, as well as a guide to purchasing and using alternatives;
- an explanatory video showing how peat is formed, its alternatives and the specific considerations that need to be taken into account when gardening without peat;
- various information leaflets that can be used when interacting with customers:
- an online training platform called ‘Torffrei-Handeln’ (Peat-Free Practices) for the growing media industry and retailers, which brings together the key project findings
The aim of all communication measures is to make knowledge from research and development accessible to practitioners – and to build trust. After all, ultimately it is not only the quality and price of the potting compost that determine success, but also the feeling it evokes.
Latest news: Display and demonstration plantings at the Weihenstephan Campus
Come and see for yourself just how successful gardening with peat-free potting compost can be. Our display and demonstration gardens at Weihenstephan-Triesdorf University of Applied Sciences (HSWT) offer practical ideas for your garden, balcony and terrace.
Location: Freising, Am Staudengarten 14, opposite the allotment garden for vegetables and fruit (see map)
Open: From early April to late September, daily from 9.00 am to 6.00 pm. Admission is free. Free guided tours are available for groups by prior booking.
