I know though that fires are bad for the environment. Burning garden material releases CO2 into the atmosphere, contributing to global warming. It also releases toxic fumes (sulphur dioxides, nitrous oxides, methane, and smoke particles) into the environment that harm soil and vegetation, and it can aggravate respiratory conditions such as asthma, COPD, and bronchitis.
So it seems counterintuitive as a gardener who enjoys fresh air, nature, and knowing what goes into my home-grown produce to pollute my neighbourhood with plumes of thick smoke. It got me thinking about why there isn’t a greater awareness of the negative impacts of fires. Why do popular television and radio programmes still recommend burning as an acceptable way to deal with garden pests and diseases, rather than looking for alternatives?
What approaches could be taken to avoid the detrimental effects of burning? Most solutions require time, space, and a little knowledge of plant diseases and weeds. Some methods are not perfect: shredding woody material for example, uses fossil fuel, is expensive, and noisy. And not all diseases are equal. Soil borne diseases like phytophthora, honey fungus, or club root are more challenging, but if you know what you are dealing with, then there are some techniques that could be implemented, even on a small scale, to be a little more sustainable.
My first port of call is to compost, ideally ‘hot composting’. This process involves creating large volumes of green and brown plant material, and then managing the compost to ensure the right balance of air and moisture to generate enough heat (50°C to 60°C for approximately a week) to successfully kill off any diseases, seeds, and weeds.
Not everyone will have the right space or facilities to successfully hot compost so if that’s your situation, then settle on placing your diseased material and weeds in your council green waste bin.
Burying infected material to prevent its spread can be an effective technique. Dig trenches at least 30cm in depth to dispose of diseased material like box blight, brown rot, and black spot. Cover over with soil to suppress the spores from spreading. I know of this process being used to control the invasive Few Flowered Leek, although the ditch may need to be much deeper as the bulbs will have enough energy to reappear.
Persistent weeds - if you see them as weeds - like dandelion, dock, ground elder, bindweed, couch grass, and horsetail can be drowned in a container of water (though this can be smelly), or desiccated (laying weeds on a rack or crate to dry) before being added to the compost pile.
A small scale method is to bag the material, excluding light and moisture, until it has rotted down or dried out completely. Then add it to your heap. This should be achievable even in a domestic setting.
Woody branches can be shredded and added to the compost heap. The smaller sized pieces break down more readily to speed up decomposition. If you have a lot of woody material it can be processed separately and reutilised as a mulch for paths and borders. Not everyone can afford a chipper or shredder, but perhaps you could club together at your local allotment, community group, or even with neighbours to hire one.
Consider dedicating an area for a dead hedge, a log pile, or just a pile of woody material. The vegetation can be left to rot down, releasing carbon more slowly than burning. It also creates habitat to benefit wildlife, providing food and cover for birds, hibernating mammals, amphibians, and reptiles. Some log piles can be a lovely feature in their own right and they encourage natural predators that will help to control plant pests too.
Another way to lose waste wood is through constructing a “hügelkultur”. This technique involves creating a mound of logs, branches, prunings, and leaves, topped with soil and organic matter. It allows the woody material to rot down slowly and increase the water holding capacity for plants that grow into the mound.
Identifying weeds and infections correctly is necessary to know how to deal with your plant waste. Some pathogens require a live host to survive, so many diseases can be effectively dealt with through composting. For example, tomato or potato blighted haulms can be composted successfully along with diseases like grey moulds, mildew, and wilts. Potato tubers though are best bagged and binned as they can harbour spores on living tissue.
Other exceptions include onion white rot and club root that are soil borne, and are not controlled through composting. I would bag and bin them in household waste, far from ideal, but still better than burning.
Prevention will minimise the need for alternative disposal. Use crop rotation to avoid the build-up of soil borne pests and diseases. Be vigilant and try to catch any potential problems before they spread, and ensure that your plants are healthy through correct spacing, correct growing conditions, annual mulching, and good hygiene such as disinfecting tools regularly.
Burn only as a last resort.
If you feel you must burn, then ensure:
• that that there is no wind and the material is dry to limit smoke
• use a specific site to minimise the damage to the soil beneath or any creatures nearby
• limit what you do burn to diseases that can’t be disposed of in any other way like coral spot, canker, fire blight, and honey fungus
In a world where the environment is fragile, we need to find ways to manage our plant waste differently by rethinking old garden traditions, and finding new sustainable options where possible to avoid lighting fires.
With a 20 year career in horticulture, Erica Randall has worked in the RBGE education department, first as Horticultural Technician, and then implementing the Fruit Garden in the demonstration area, moving on to later develop a kitchen garden for local Edinburgh restaurateurs, plant and design Archerfield Walled Garden in East Lothian, and most recently oversee the National Trust for Scotland gardens Priorwood and Harmony in Melrose, as Head Gardener. Erica is now returning full circle to become an online tutor for the RHS Level 2 Certificate in Principles of Plant Growth and Development at RBGE. This will combine her three main passions: creativity, plants, and skill sharing.