The Healthy Vegetable Garden: A natural, chemical-free approach to soil, biodiversity and managing pests and diseases

Introduction

Nothing gives me greater pleasure than to wander around my garden, admire the flowers and enjoy the wealth of animal life that is drawn into my green space, or sit in the shade of an apple tree watching insects and listening to bird song. My garden is not a tidy space; weeds don’t bother me, and my shrubs are not pruned to within an inch of their life. My aim is to establish as much diversity as possible in order to produce a healthy growing space.

CREATING A HEALTHY GARDEN

There are no short cuts when you are trying to create a healthy garden. It takes time to build a healthy soil and attract the diverse life that you need. I bought a small farm 16 years ago that had been managed conventionally, with regular applications of fertiliser and pesticides. Many of the soils were compacted from the use of heavy machinery. I put the land into organic conversion and started the slow process of improving the soils as well as boosting biodiversity, creating new habitats, planting trees and letting areas rewild. It’s these principles that I have also been applying to my garden, albeit on a much smaller scale, helping it to become more resilient and better able to cope with pests and disease and all the challenges that climate change will pose in the coming years, be it flood, drought or a myriad of pests new to our shores.

I studied botany and ecology at university, so I automatically look to nature for ideas. The one habitat that has influenced me more than any other is the rainforest - it never fails to impress me with its immense diversity and incredible stability. When you study ecology, you learn that the more stable habitats are also the most complex and that they have the most resilience to change. It is within these habitats that you see the most amazing relationships build up between plants and animals. The same is true of our soils. To be healthy and stable, soils need a diversity of living organisms, from bacteria and fungi through to nematodes and earthworms.

We need to treat our gardens as a complete system and make use of ecological relationships that have evolved over millennia. Plants have evolved alongside their pollinators and pests, and they have developed mechanisms for dealing with these pests. They work with beneficial insects that attack the pests by supplying them with food in the form of pollen, nectar, root exudates, nutritionally rich leaves, seeds and fruits. You get even more complex relationships in the soil, where beneficial bacteria and fungi will live on the surface of roots and protect them from attack by pathogens.

Understanding your local environment is important, too. The world-renowned Professor Daniel Janzen has studied the tropical forests of Costa Rica since the 1970s and seen vast swathes of forest cleared across Central and South America to make way for cash crops such as banana, cacao and rubber. He has long argued that crop production in tropical regions must be based on ecological knowledge. The crops should be local in origin so they are adapted to the environment and suited to local needs, rather than the unsuitable crops that are grown purely for the export market, with little benefits to the community. These ideas apply just as much to our gardens as to commercial crops. Learning about a plant’s ecology - where it comes from, what conditions it needs, whether it’s insect- or wind-pollinated - will help you choose the place in the garden where it is going to thrive. A Mediterranean plant, for example, which loves heat and free-draining soils, is never going to thrive on a heavy clay soil that gets waterlogged in winter.

The fabulous Vallée de Mai, on the island of Praslin in the Seychelles, has a huge diversity of palms.

REGENERATIVE GARDENING

There are some inspirational farmers and growers working within regenerative and organic farming who have taken soils damaged by decades of intensive cultivation and set about improving them. They don’t use artificial fertilisers and look to biodiversity to help control pests and disease. They may be working on a larger scale than a garden, but many of their ideas work just as well in small spaces. So, to start with, I am going to outline the principles of regenerative, agroecological and organic farming, plus permaculture, as I will come back to these principles throughout the book.

Regenerative farming

The relatively recent concept of regenerative farming, which is also referred to as conservation agriculture or ecological farming, focuses on improving and revitalising soil health through increasing biodiversity, enriching the soil with organic matter, making good use of water and helping to reverse climate change, but, unlike organics, there are no restrictions on the use of artificial inputs, such as weedkillers and pesticides, which can harm soil life and beneficial insects.

Agroecology

This is all about a whole-farm approach, boosting plant diversity to support as wide a diversity of animal life as possible, with the provision of lots of different wildlife habitats. It’s a circular, closed-loop system, which means trying to keep waste to a minimum and making use of secondary products. For example, a farmer might feed waste milk whey to pigs or spoilt grain to poultry. We are seeing this approach develop into urban agroecology through urban farms and also vertical gardening where plants are grown on tiered surfaces on fences and walls. Gardeners can take on board a ‘whole garden’ approach to keep their growing spaces diverse and healthy, and to keep pests and disease at an acceptable level. When applied to the garden, a whole-garden approach also means green waste going in the compost bin or wormery, wood being left to rot, making use of homegrown fertilisers, and much more.

Organic farming and growing

One of the oldest forms of agroecology is organic, which is the gold standard in my opinion. Many gardeners say ‘I grow organically’ but a lot of them think this simply means growing without the use of artificial fertilisers and pesticides. In fact, organic is very much more than that. The definition of organic agriculture given by IFOAM - Organics International is:

…a production system that sustains the health of soils, ecosystems, and people. It relies on ecological processes, biodiversity and cycles adapted to local conditions, rather than the use of inputs with adverse effects. Organic agriculture combines tradition, innovation, and science to benefit the shared environment and promote fair relationships and good quality of life for all involved.

Permaculture

This is a sustainable system of living created by observing natural systems. The term permaculture was first defined by the Australian Bill Mollison who, in his 1978 book Permaculture One written with David Holmgren, defined it as: ‘The conscious design and maintenance of agriculturally productive systems which have the diversity, stability, and resilience of natural ecosystems. It is the harmonious integration of the landscape with people providing their food, energy, shelter and other material and non-material needs in a sustainable way.’ I’ve used a lot of permaculture ideas when designing my growing spaces.

WHAT DOES A HEALTHY GARDEN LOOK LIKE?

First, there’s lots of plant diversity. That means both different species and plant types in the form of annuals, perennials, trees and shrubs. There is diversity, too, within the vegetables you grow and also temporal diversity, with crops at different stages of their life cycle. And they all look to be in good heath. In addition, there is a patchwork or mosaic of habitats, such as long and short grass, herbaceous beds and shrubs, walls and fences, fruit trees, a pond and some wild corners, which all help the garden to support a diverse array of wildlife. In addition, a healthy garden is not just about a low level of disease and pests; it is also about maintaining a balance in the soil, so that the plants and soil life can combat disease and keep pests at bay. The aim is not to get rid of them completely, but to keep them at a low level so there is little or no damage.

All in the soil

One of the keys to this diversity is a healthy soil - it underpins everything we do in the garden. When we improve our soils, for example, we sequester more carbon, which helps in the battle against climate change. Our soils will retain more water, improving the local water cycle and reducing erosion. Plus, a healthy soil will help us to create something that is vital to our own well-being - healthy food.

The idea that a healthy soil is important to the health of crops is not new - generations of gardeners around the world have made this link. Some years ago, I visited the fabulous kitchen gardens at Monticello, in Virginia, in the US, the home of Thomas Jefferson (1743–1826), who loved gardening and growing vegetables. He kept a diary and frequently commented about the insects in his gardens, both beneficial and pests, including this in a letter to his daughter:

We will try this winter to cover our garden with a heavy coat of manure. When earth is rich it bids defiance to droughts, yields in abundance and of the best quality. I suspect that the insects which have harassed you have been encouraged by the feebleness of your plants, and that has been produced by the lean state of the soil. We will attack them another year with joint efforts.

The terrace of vegetable beds at Monticello, Virginia.

Homegrown organic vegetables and fruit.

One of the founders of the organic movement, Sir Albert Howard (1873–1947) wrote many books on the subject of soil health and composting based on his 25 years of research in India. Louise Albert, his second wife, wrote of his work in Sir Albert Howard in India:

A fertile soil that is teeming with healthy life in the shape of abundant microflora and microfauna, will bear healthy plants, and these, when consumed by animals and man, will confer health on animals and man. But an infertile soil, that is, one lacking sufficient microbial, fungous and other life, will pass on some form of deficiency to the plants, and such plant, in turn, who pass on some form of deficiency to animal and man.

Research shows that fresh produce provides people with calories but not the essential minerals and vitamins needed for health. Nutrient density, the measure of the amount of nutrients you get in your food for the number of calories it contains, has declined greatly over the last 70 years. Since 1950, levels of calcium, iron and vitamins B and C in particular have fallen. For example, according to the USDA (US Department of Agriculture), broccoli in 1950 had calcium levels of 12.9 mg/g, but by 2009 this had fallen to 4.4 mg/g. This is a direct result of intensive farming where soil is tilled, fertilised and treated with pesticides, producing crops that have greater yields, but which lack nutrient content. It highlights how important it is for us to have healthy soils so we can grow truly healthy vegetables.

YOUR OWN GREEN SPACE

Private gardens and allotments in Britain are estimated to cover an area of around 4 million hectares (10 million acres); that’s more than all of the country’s nature reserves combined. Of this space, around 500,000 hectares (1,240,000 million acres) are classed as urban residential gardens, so they are critical in providing habitats for plants and animals and creating green links between public open spaces and farmland, as well as for producing more homegrown fruits and vegetables.

If all of us did our bit and created a more diverse, healthy ecosystem in our own green spaces, we would be contributing to the overall goal of a much healthier environment. A classic example of what can be achieved in a small space in an urban setting is Rene Zazueta’s tiny backyard - a concrete lot in Berkeley, California - that had been damaged in the Loma Prieta earthquake of 1989. He cleared away the scrap, concrete and contaminated soil and created an experimental agroecological garden. He planted a diverse mix of fruit trees along the fencing and intercropped vegetables with flowering plants in his raised beds. His growing spaces were fuelled by a compost system that used all the food and plant waste, together with compost teas and worm casts. The end result proved that it is perfectly possible to apply ecological principles to food production in an urban setting.

In the chapters that follow, I will look at ways that you can work with nature to build your soil, grow healthy plants and lessen the incidence of pests and disease. In doing so, you can create a more resilient growing space which is better placed to cope with the stresses that climate change is sure to throw at us in the years to come.

PART 1 Building a healthy soil

CHAPTER 1

Soil basics

‘Only 60 years of farming left if soil degradation continues’, screamed the headlines on World Soil Day (organised by the United Nations) in 2014. The United Nations warned that the heavy use of chemicals, combined with deforestation and global warming, were degrading our soils. Soils around the world were heading for exhaustion, with an estimated 60 harvests left before they became too barren to feed the world. There was little evidence to back up this claim until 2020, when a new study found that 90 per cent of conventionally farmed soils around the world were getting thinner and had less than 100 years of harvests left. There was an optimistic note, though, for it was pointed out that soils managed with conservation techniques had much longer predicted life spans.

So much soil has literally been blown away as a result of intensive farming practices, as shown here in a field in Lincolnshire.

WHAT ABOUT GARDEN SOILS?

The headlines referred to farmland soil, but what about the soil in our gardens and allotments? Have our gardening practices been improving or harming our soils? It seems that many of the country’s allotmenteers have actually been doing quite well. In 2014, scientists at Sheffield University found that allotment soils were significantly healthier than soils on intensively farmed land. Taking samples from allotments, parks and gardens in Sheffield and the surrounding farmland, Dr Jill Edmundson found allotment soil to be generally healthier and with less compaction than farmland soils. Of the plots sampled, the allotment holders had worked their plots on average for 5 years and a few for over 15 years - plenty of time for their practices to have an effect. Nearly all composted their green waste, and most allotmenteers added manure and fertilisers such as chicken manure, fish, blood and bone, tomato feed and liquid seaweed. The study showed that it was possible for small-scale urban food production to take place without the loss of soil quality associated with conventional intensive farming.

Productive organic allotments in Somerset.

However, the same may not be true for all garden soils. Go into any garden centre and you will see shelves stacked with a huge variety of chemicals for use in the garden - lawn treatments, fertilisers, fungicides, pesticides, and more. They may provide the results craved by many gardeners but, in the long term, all they do is damage the soil and its inhabitants and create imbalances. Before you know it, more chemicals are needed to maintain that control and, from then on, it’s a downward spiral. I talked to one gardener who had just moved house and then discovered her new soil to be in dire straits. Superficially, the garden appeared well looked after and healthy: the shrubs were pruned, the beds were full of interesting plants and the lawn was immaculate. But the perfect, weed-free lawn was a warning sign. Clearly it had been fed, mown and trimmed, but the removal of a sod of grass showed that the grass roots hardly extended into the thin soil beneath. Despite the outward impression, the garden soil was highly degraded, mirroring what we see in intensive agriculture, a consequence of relying heavily on synthetic fertilisers and pesticides rather than adding compost and mulch to build up the organic matter in the soil and feed the soil microbes.

The problem with fertilisers

When you add organic matter to healthy soil, microbes kick into action, breaking it down and releasing nutrients in a form that plants can use, whereas adding a synthetic fertiliser to your soil upsets the balance of soil life. When the fertiliser label says: ‘readily available to plants’, it means just that - it is in a form that plant roots can take up straightaway. The nutrients in the fertiliser bypass the soil food web and, instead, go directly to the plants’ roots. I describe these instant nutrients as a ‘plant-style ready meal’. The trouble is that continued use of these fertilisers results in many specialist microbes being put out of work and they then disappear from the soil community. The longer you continue to apply fertilisers, the lower the diversity of soil microbes becomes. Once the soil microbes disappear, the soil’s ability to recycle nutrients decreases and the plants become dependent on fertiliser to supply all their nutritional requirements. The gardener must continue to feed the plants and the soil becomes nothing more than an anchoring material and water reservoir.

Of course, it’s not just fertilisers that are causing problems. Pesticides, fungicides and herbicides can do just as much damage to soil life, disrupting the complex food web and putting things out of balance, and that is when pests and pathogens can start