n this study the effects of growing annual and perennial plant species in five growing media blends; one peat-based, two peat-reduced and two peat-free. Three main components were used in the blends: sphagnum peat (P-Soil (PS), Wood fiber substrate (WFS), Peat reduced blend (PRB)), coarse wood fiber (Fibergrow®) of Norway spruce (Picea abiens) (WFS, PRB, Circle soil (Circle), PFB) and garden/park waste-based compost (Circle, PRB, PFB). The peat-based reference (P-Soil) contained 10 vol.% composted bark in addition to sphagnum peat. pH in the blends ranged from 5.1 to 6.4. Both annual and perennial plants were tested in the five blends, and large differences in growth and vitality of plants grown in the different blends were observed. The performance of most plant species grown in Circle, PRB and PFB was characterized as satisfactory, while P-Soil gave the best results and was used as reference as it is commonly used in the plant nursery. Plants grown in WFS showed generally weak growth and the plant growth was characterized as unsatisfactory. However, WFS and PRB performed satisfactory to seedlings of Rhododentron uniflorum, while Circle and PFB failed to give satisfactory growth of rhododendron seedlings. Although all blends were basic fertilized with different types of compound mineral fertilizers, chemical analyses showed significantly lower concentrations of CAT-soluble plant nutrients in WFS compared to the other blends. N-immobilization during storage in plastic bags may have occurred for WFS, which has very high C/N-ratio. In the blends with compost and Fibergrow® the expected levels of mineral N were found, and no N-immobilization occurred. In the blends with compost almost all mineral N was present as nitrate-N, while ammonium-N dominated in P-Soil. There were no large differences in root development between the five blends, and the root growth in WFS was good despite significantly smaller plants than in the other blends.

To support and facilitate the UK's transition to peat-free horticulture, there is a strong need for propagation media formulations which deliver plant performance results comparable to those achieved with peat-based media. Commercially available peat-free propagation media which are manufactured for the professional ornamental plant sector are, to date, primarily composed of coir and wood-based products. These blends may include mineral or organic additives, wetting agents, fertilisers and biological amendments. These supplements will influence a media's physical, chemical and/or biological properties, which will impact plant development. The propagation industry has highlighted the need for support through scientific research to achieve the peat-free transition due to challenges with current peat-free propagation media including cohesion, movement of media, and transplant handling, which increases the need for characterisation. These factors combined with differing water and nutrient management by growers collectively impact propagation success, making holistic understanding crucial. It is essential to address these challenges through large-scale nursery trials in a commercial setting, which can assist through the demonstration of the practical differences and requirements of each currently available media. However, to understand the technical aspects of peat-free media formulations, research into the properties of these media is necessary for further development. Despite the progress made in peat-free growing, there remains a lack of publicly available information describing the physical, chemical and biological properties of currently available peat-free propagation media for professional horticulture. This article documents the characterisation of various peat-free propagation media, considering a range of properties: physical (e.g. particle size distribution and water holding capacity), chemical (e.g. total and available nutrients) and biological (e.g. microbial activity and ability to support plant growth). The evidence-based findings aim to provide suggestions to overcome specific challenges faced by the ornamental horticulture propagation sector. 

Due to the economic importance of protected strawberry production and its relatively high environmental impact, more sustainable cultivation methods are needed. This study compared alternative growing media effects on plant growth and berry production. 'Sonsation' strawberries were grown in six substrates: 100% peat, 100% wood fibre, 50% peat/50% wood fibre (with and without fertilizer), and two compost and wood fiber-based products ('Nittedal' peat-free and '29 mod' peat-reduced). Irrigation treatments included standard fertigation and pure water (for 'Nittedal' and '29 mod'). In the first five weeks, the tallest (35 cm) and shortest (30 cm) plants were recorded in '29 mod' and 'Nittedal' grown on pure water, respectively. The other treatments showed consistent plant height between 33–35 cm. While peat-based media resulted in the highest yield, alternative materials performed similarly, except for a lower yield in the peat-free 'Nittedal' with pure water, with no added fertilizer. This treatment also had fewer inflorescences per plant and lower biomass production. In addition, pH and electrical conductivity measurements indicated that peat-reduced and peat-free substrates maintained optimal pH levels for strawberry growth (between 5.5-6.5). Overall, while peat-based media produced the best-performing plants, the more sustainable alternatives demonstrated comparable performance, making them viable options for strawberry cultivation.

The reduction of peat use without compromising crop yield and uniformity is one of the current core topics in German horticultural research. Two interrelated approaches are generally utilized for peat-reduced production systems: substituting peat and reducing the amount of substrate used per plant. This study investigates the influence of press pot volume on the yield formation of iceberg lettuce (Lactuca sativa var. capitata) with the aim of reducing peat use through minimizing substrate demand. In 2022 and 2023, three identical experiments were conducted in spring and summer under northern German climate conditions, comparing five different press pot sizes ranging from 32 to 66 cm³. This could result in potential substrate savings of up to 52%. During the transplant nursery phase, data on shoot and root mass and leaf area were collected. After transplanting in open field, growth was monitored through five succeeding harvests.

At planting, plants in the 32 cm³ pots showed an increase in specific leaf area of on average 56% compared to the 66 cm³ reference pots. Nevertheless, none of the recorded transplant parameters was a suitable predictor for field growth rates. Mixed model analysis revealed significant effects of the experiments (growing season). Hence, each experiment was interpreted individually. Growth modeling showed only a slight harvest delay until reaching 400 g head weight, with a maximum delay of 2.4 days in Exp. 2 (summer). However, the distribution of head sizes tended to be wider for the smallest pots, indicating a less uniform stands at harvest.