Earth Day 2024 is upon us; a day to not only demonstrate our unwavering support for environmental protection, but, perhaps, to re-visit some long-held assumptions. So, as gardeners, how can we be more mindful of Mother Nature this spring?
Thanks to a generous helping of rainfall and a smattering of sun, it seems the gardens have finally awoken from their winter slumber. But along with new growth, comes seasonal pests. Slugs are tunnelling in the tubers, aphids are sucking the sap from the salvias, and box-tree caterpillars are blighting the Buxus.
Once again, we find ourselves faced with the gardener’s perennial question: How do I combat the spring-time assault, but in an organic fashion?
To answer this, one would be forgiven – particularly on Earth Day – for asking: What is meant by “organic”?
A bird’s-eye view
At an agricultural level, it’s rather straightforward, and the UK government has issued a specific process-driven list of compounds that can be used on a crop for it to be sold as organic. For hobby gardeners, though, the definition seems to be more nebulous than that. When we say “organic”, there is an unwritten agreement among green-fingered friends that we are referring to any “natural” horticultural practice. “Organic” is, in other words, a rejection of more conventional techniques involving synthetic pesticides, insecticides or fungicides – some of which have proven to be a major contaminant of our waterways, earth and air.
Today of all days, however, we should push ourselves to be more nuanced in our outlook. This is because not all “natural” compounds we spray onto our beds are made equal – at least, not in the eyes of some within the organic movement. Indeed, some naturally-occurring compounds are more damaging to nature than we might expect. This, dear readers, is the point around which the organic tribe breaks in two.
The organic culture: Two tribes
On one side we have the pragmatic, casual supporter of the organic movement. A gardener in this camp may happily (as I have in the past, admittedly!) spray “tobacco tincture” onto his or her perennials; confident in the knowledge that nicotine is a naturally-occurring compound, and a highly effective pesticide. This brownish mixture, created by boiling or steeping nicotine-rich tobacco leaves in water, is toxic to many of the nasties that feast and fornicate in our beloved borders, and, crucially, is not concocted in a factory.
The second, more purist camp, however, would argue that if a plant cannot be grown without requiring pesticides, it should not be grown at all. Nicotine, for example, is too indiscriminate, biochemically. While not synthetic, it is so powerful that it will also exterminate any beneficial insects and bugs in the area. This might include, for instance, ladybirds, which target and consume aphids and scale insects. This evangelist approach to organic gardening, then, says there are no corners to be cut. It emphasises the importance of biodiversity and upholding the natural cycle of prey and predation; using only nature itself to combat pests. This is a more hands off approach, but it does yield results when a balance is struck.
Discriminate pesticides
So what are the more discriminate pest-control options for the organic-minded gardener this spring?
First approaches should always be preventative. It must be remembered that a pest infestation is often symptomatic of a more underlying problem with a plant’s health. Indeed, pests tend to go for easy targets, or “low-hanging fruit”, as it were. This means plants with a weakened “immune system”, or inability to fight back – which in turn, will be the result of all kinds of factors, such as inconsistent watering, poor soil fertility or inappropriate PH levels, not enough (or too much!) sun, low crop hygiene, insufficient airflow, excessive nitrogen, and so on.
Once these factors have been fine tuned for each plant, beyond mechanical removal or gene editing for resistance, there are reactionary and organic (in the purest sense) options available to hobby gardeners. These come in three forms:
Chemical and selective pesticides: Ingredients for these environmentally-friendly tinctures can be grown in the garden, and mixed in the potting shed. One example is a spray containing pyrethrum – the endogenous compound found in Chrysanthemum cinerariiflolium. To make the spray, simply cut off your chrysanthemum flower heads whole, ideally when the first petals have just opened. Hang to dry in a cool, dark place, like your shed. Once crisp, immediately grind the petals into a powder and mix half a cup powder with a litre of water. Apply liberally to the leaves of your infested plants. Other such repellents include capsaicin found in chillies, fatty acids such as olive oil, and even isoprenoids endogenous to Ginkgo Biloba or citrus fruits. If you do decide to deal with pests and diseases via commercial products, always read the label, and refrain all together if there are beneficial insects around!
Biological pesticides: This approach uses nature itself to fight the pest. Nematodes (roundworms or eelworms of the phylum Nematoda) for instance, can be used as a biological vector to target slugs and snails. They attack the gastropod molluscs by entering body openings and releasing bacteria which prevents them from feeding. Other examples include the introduction of parasitic wasps (Microctonus brassicae) to greenhouses, which have been found to lay eggs within the body of beetles.
Companions and poly cultures Polyculture is the practice of growing more than one plant species, side-by-side, at the same time. The increase in plant diversity ensures the soil’s available elements are absorbed in a more balanced way, resulting in a reduced risk of plant ill-health, and in turn, a reduced need to reach for the fertilisers and pesticides. Examples of annual crop companions for the allotment include carrots, lettuce and onions. The thinking is that onions grow taller than carrots, so they will not be shaded. Lettuce needs less light, so being shaded by the carrots is okay. What is more, the root systems of these crops dig to different depths and so will not impede each other. Overall, this means a healthy crop, with a more developed ability to fight pests.
Earth Day, like an organicist, acknowledges the importance of every individual’s impact on the health of Mother Nature. As gardeners, at the coalface of the environment, today offers unique opportunity to take stock of our traditional approaches, re-evaluate what it means to maintain biodiversity, and above all, learn. It is my conviction that your organic journey this spring will be as rewarding and fulfilling as any other.
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