Home & Garden
Carbon Gardening And The Magic Of Mulch Landscape designer Sarah Murch urges gardeners to step up to the climate crisis challenge this spring.
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ike it or not climate crisis is upon us. This time, ten years ago, I drove home excitedly with a van full of plants to start my new garden. It wasn’t a great start. An arctic snap with heavy snow froze them all dead in their pots. Since then, snow has become a distant memory, and I can count on one hand the frosts this season. Winters are milder. Unpredictable weather patterns challenge our gardens. Take the heatwave of summer 2018, a prolonged drought followed by little rainfall through to summer 2019. Then came a year’s worth of rainfall in one month with some of the worst local flooding in the UK.
Gardening to combat climate change We all contribute to global CO2 emissions. While it’s easy to blame landowners and farmers for habitat loss, soil degradation and environmental crises, I feel it’s time we gardeners shouldered some responsibility for our own patch of land. Individually you might wonder what difference your garden makes, but collectively our UK gardens reportedly cover 1 million acres. Together gardeners have the opportunity to help combat climate change with a resource right under our feet: Soil.
Soil as a carbon sink As plants grow, they photosynthesise, drawing CO2 from the atmosphere, depositing it in the soil as carbon. Our soil becomes a Carbon sink. The potential for soil to sequester CO2 from the atmosphere is well documented. Scientists claim agricultural land worldwide could sequester up to 1.85 billion tonnes of carbon per year, becoming an important pathway towards limiting global warming to the 2ºC target of the Paris Climate Agreement 2015.
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So how do we capture carbon in our gardens? Undisturbed, soil can lock carbon for thousands of years in the form of soil organic matter. Soil with a higher organic content is darker, more fertile and has capacity to store more carbon. However, once the soil is disturbed, by hoeing, tilling, rotavating or in agriculture through ploughing, the carbon stored safely in our soil oxidises on contact with the air and is released back into the atmosphere as CO2.
So how do we maximise carbon capture and storage in our gardens? Simple. Improve your soil and don’t dig. Start by incorporating compost or soil conditioner which improves your soil’s organic matter. As a guide, I work on a 50mm layer of soil conditioner per m2 of soil. Clay and sandy soils could require more. Soil conditioners are readily available bagged or loose, with a choice of composted farmyard manure, spent mushroom compost, composted green waste, or even better make your own compost like we do from farmyard manure and garden waste. Once you have cultivated your soil, tickled in the soil conditioner, raked it level, planted your border or sown your vegetables, that’s it. Job done. You leave it alone, never dig it, fork it, tickle it, hoe it, or reach for the rotavator again. Next, keep your soil friable, weeds at bay and lock in the carbon by adding a mulch.
The magic of mulch Mulch is a layer of organic material spread over your soil’s surface. Mulch can be composted bark or wood chips, chopped straw (Strulch), leaf mould or composted green waste. Home-made mulches include shredded garden prunings, (avoid conifers),
