Check the list of ingredients on bags of potting soil and soil conditioners at your local garden center and you’ll probably find peat among the entries. The purpose of this dry, lightweight potting medium is to improve drainage, providing plant roots with access to water, oxygen, and the nutrients required for growth. Peat doesn’t supply the nutrients but facilitates their absorption by changing the structure of the soil.
When added to dense and saturated clay soils, peat breaks the soil apart, creating space for air to infiltrate. These air pockets allow plant roots to absorb oxygen, an element essential for plant health. If a plant’s roots can’t access oxygen, the plant may die. Plants in this condition often are described as having suffocated or drowned from wet, airless soil.
When added to sandy soils, peat slows drainage, enabling plants to absorb nutrients that usually wash away before they can be used. Sand particles are large but have less overall surface area than clay particles, which reduces the amount of water the sand can retain. Peat’s ability to expand when wet adds needed texture and surface area to these loose soils.
Plants thrive in response to these changes in soil structure, which is why peat has been a popular gardening and horticultural product since it began to be marketed in the mid-1900s. But this use of peat comes at a high cost. To extract peat, wetland areas known as peatlands are drained, and the mined peat is dried over time. These processes release carbon dioxide, one of the gases responsible for a warming climate. According to the International Union for the Conservation of Nature’s IUCN Issues Brief: Peatlands and climate change, drained and otherwise damaged peatlands are responsible for 5% of annual worldwide emissions of greenhouse gases. Damaged peatlands cover 0.3% of the Earth’s land surface, while total peatlands, intact and disturbed, make up 3% of the planet’s landmass. Imagine the multiplier effect on emissions if peatland drainage expands.
Peat is a resource that takes millennia to develop and only in the right conditions. Sphagnum mosses, grasses, sundews, sedges and other peatland plants must be submerged in water and left undisturbed after dying. Decomposition by microbes occurs, but the limited oxygen in the wetland conditions inhibits microbial respiration, which slows the breakdown process. Over time, as plants continue to die, more plant material accumulates than decays. Carbon removed from the atmosphere during a plant’s life, through photosynthesis, is preserved in the layers of semi-decayed plant material, which in some peatlands can be 20 feet deep. As long as peatlands are not mined or otherwise damaged, this carbon is locked away, in such quantities that peatlands store more carbon than the vegetation of all other landforms on Earth combined.
For decades, gardeners and horticulturalists have worked to reduce the use of peat and to preserve peatlands. These efforts have been particularly forceful in the United Kingdom, where peatlands make up 12% of the land area and, in 2020, peat accounted for 41% of all plant growing media, according to Peat-free Horticulture: Demonstrating Success. The UK’s Royal Horticultural Society is a leader on peat-free initiatives and is committed to eliminating peat from RHS gardens, plant shows, and plant sales by 2025, as outlined in the RHS peat policy. It also is committed to educating its members and the general gardening public on the value of peat and the environmental impact of its continued use for gardening.
The RHS has been researching substitutes and offers peat-free composts for sale. If gardeners and the horticultural industry beyond the UK are to go peat-free, alternatives to peat need to become better known and easy to purchase. Until peat-free potting soils and soil conditioners are more widely available in the US, which obtains most of its horticultural peat from Canada, consider one of these options:
Coconut fiber, or coir, is waste generated from the coconut industry, and is described as a reusable and sustainable resource, although it must be processed before use and shipped considerable distances. The fibers are lightweight and expandable, similar to peat, and improve soil water retention and air infiltration capabilities.
Commercially available or made at home, compost is decomposed plant material that adds nutrients to the soil and improves aeration. In contrast to peat, compost is the result of an aerobic process, with microbes using oxygen to break down a mix of green (vegetable scraps, grass clippings) and brown (paper, straw, wood chips) plant matter.
Leaf mold is a soil conditioner and mulch that is the product of fall leaf drop. Leaf mold can be created simply, by letting leaves accumulate in garden beds in the fall and working them into the soil as they decay, or with a bit more effort, by shredding the leaves and keeping them slightly wet to accelerate the decaying process. As with compost, leaf mold adds nutrients to the soil.
Another option? Work with existing conditions. Instead of trying to transform soil into an unrealistic ideal that is not typically found in your region, choose plants that tolerate the clay, sand, or other soil conditions in your garden. This naturalistic approach connects the garden to the local environment and may lead to greater sustainability over time.
Whether classified as a fen, mire, tropical swamp forest, or permafrost bog, peatlands are landforms of such environmental significance that organizers of COP26, the 2021 UN Climate Change Conference, invited attendees to an in-person and virtual Peatland Pavilion to describe the role of peatlands in addressing climate change. With their unique ecology and thousand-year histories, peatlands also are places of mystery and beauty. Reconsidering peat in the garden is one way to contribute to their survival.
Notes
- International Union for the Conservation of Nature. IUCN Issues Brief: Peatlands and climate change. Last reviewed: November 2021. Accessed January 22, 2022. https://www.iucn.org/resources/issues-briefs/peatlands-and-climate-change
- Holmes, S. & Bain, C. (2021) ‘Peat-free Horticulture – Demonstrating Success’, IUCN UK Peatland Programme, Edinburgh. October 2021. Accessed January 22, 2022. Download from the Demonstrating Success Booklet Series website at https://www.iucn-uk-peatlandprogramme.org/resources/restoration-practice/demonstrating-success
- Royal Horticultural Society. RHS peat policy. Accessed January 22, 2022. https://www.rhs.org.uk/about-the-rhs/policies/rhs-statement-on-peat
- IUCN UK Peatland Programme. Peatland Pavilion at COP26. Accessed January 22, 2022. https://www.iucn-uk-peatlandprogramme.org/events/peatland-pavilion-cop26
If you’d like to read more . . .
Bek, D., Lennartsson Turner, M., Lanari, N., Conroy, J., & Evans, A. (2020). Transitioning towards peat-free horticulture in the UK: an assessment of policy, progress, opportunities and barriers. https://hta.org.uk/uploads/assets/219d3ce6-e9a2-4659-b0a52d7a1bd6dd1e/FINALCOVNTRYUNIREPORT-HTAGMAFinalCoversauthors29Sept20-1.pdf. Accessed January 24, 2022.
Birnbaum, Christina & Wood, Jennifer & Lilleskov, Erik & Lamit, Louis & Shannon, James & Brewer, Matthew & Grover, Samantha. (2022). Peatland Degradation Reduces Microbial Richness and Alters Microbial Functions in an Australian Peatland. Accessed January 24, 2022. https://www.researchgate.net/publication/357855371_Peatland_Degradation_Reduces_Microbial_Richness_and_Alters_Microbial_Functions_in_an_Australian_Peatland
CongoPeat: Past, Present and Future of the Peatlands of the Central Congo Basin. Accessed January 24, 2022. https://congopeat.net/
Gustaf Hugelius, Julie Loisel, Sarah Chadburn, Robert B. Jackson, Miriam Jones, Glen MacDonald, Maija Marushchak, David Olefeldt, Maara Packalen, Matthias B. Siewert, Claire Treat, Merritt Turetsky, Carolina Voigt, Zicheng Yu. Large stocks of peatland carbon and nitrogen are vulnerable to permafrost thaw. Proceedings of the National Academy of Sciences Aug 2020, 117 (34) 20438-20446; DOI: 10.1073/pnas.1916387117. Accessed January 24, 2022.
IUCN UK Peatland Program. International Union for the Conservation of Nature, National Committee, United Kingdom. Accessed January 24, 2022. https://www.iucn-uk-peatlandprogramme.org/
Martignoni, Jimena. “Bog Wild.” Landscape Architecture Magazine. June 2022, 112 (6) 100-113.
Nair, Anila. “A Case Against Peat.” Fulton From the Ground Up. University of Georgia Extension. June 15, 2021. Accessed January 24, 2022. https://site.extension.uga.edu/fultonag/2021/06/a-case-against-peat/
Peat and Peatlands. Canadian Sphagnum Peat Moss Association, New Brunswick Peat Producers Association, Quebec Peat Moss Producers Association. Accessed January 24, 2022. https://peatmoss.com/
Peatlands. International Peatland Society. Accessed January 24, 2022. https://peatlands.org/peatlands/
“What’s so special about peat?” National Trust. Accessed January 24, 2022. https://www.nationaltrust.org.uk/features/whats-so-special-about-peat
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