Provide shade, make compost and leave the weeds: six ways to heatproof your garden | Gardens

Gardens often act as a middle ground between our built-up, manufactured indoor lives and the world outside. The garden, whether it is a few pots, an allotment or something much larger, is a tiny slice of the rest of the ecology of our globe – and it teaches us about the gossamer threads that hold these things together.

In the blast of the UK heatwave in July, we watched our gardens curl and crisp. Stalks bent and wilted; leaves scorched and then browned. How much of your green space survived depending on how you had been tending those delicate threads.

The next heatwave might last for longer. It might arrive with stronger winds, or leave behind wilder, wet days. The winter will present its own challenges – more flooding, perhaps, as baked-hard soils struggle to soak up the rain. We need to prepare; this weather isn’t going away. The question is: how?

Heatproofing your garden begins before you step foot in it. Our gardens, their inhabitants, our world, is under threat because of rampant fossil-fuel usage and yet some of the biggest polluters are unwittingly bankrolled by us, through our current accounts, mortgages and savings. Choosing a bank that is committed and transparent about tackling the climate crisis should be high on your to-do list. Tell your old bank why you are leaving; tell them that you are a gardener and it is your job to foster what is left. Then we can begin the good work of making sure our gardens are resilient enough to deal with whatever the weather throws at them.

Considering dry plants? Dig a little deeper

Woman farming on an organic farm
Most of the UK sites on clay, so plants and crops should be chosen with this in mind. Photograph: vgajic/Getty Images

It is easy to imagine that the simplest move might be to replace the plants that failed with dry garden plants, those Mediterranean types that thrive in baked places with intense suns. But to grow these plants you need free-draining, low-nutrient soils that are made up of grit, gravel, rocks and sand – and the UK is not blessed with these.

Most of the UK sites on clay; try to grow dry garden plants on these soils, even with the addition of extra grit and gravel, and you may struggle. The soils that dry garden plants thrive in are lower in nutrients than clay- or humus-rich soils and thus the plants grow more slowly. They do not grow lush or rich; instead, they grow tough, which protects them in the heat. Grow these plants on richer soils and they grow too fast, too leggy and too weak.

If the summer doesn’t get them, they will rot in the wet of winter. If you have a gravel pit or are on urban rubble, then by all means these are your plants. But if you are on clay, gleys or heavy chalk marls – anything that becomes sticky and unworkable in winter – then the solution is not to rush out to buy gravel or grit to change your soils, for there is no sustainable extraction of gravel, grit or sand. These materials are heavy to extract, to bag and to transport, and the removal of them radically changes the soils and the environment from which they came.

‘Right plant, right place’ has never been more true

Woman cutting dahlia flowers
Plants with fat tubers, such as dahlias, might fare better in the heat. Photograph: Betsie Van der Meer/Getty Images

The things that failed in your garden were most likely on the edge of what they could tolerate, whether that was light or soil conditions, competition from other plants or exposure to wind. Anything that had to compete with major tree roots probably suffered as the tree’s vast root system drew in any surface moisture available to support its bulk.

Don’t try to replace like with like. If a plant completely failed, compost it and replace it with something tougher. We have been allowed to believe that we are gods in our gardens. We often plant what we want, not what the garden needs. Now, we have to heed a new religion, honoring soil and the ecosystem.

These tough plants have to be drought-tolerant and capable of wet winters. These are not necessarily dry garden plants, although they share their resourcefulness and their thicker or hairier (or both) leaves that don’t frazzle in the heat – things such as verbascums, Stachys byzantine, Verbena bonairensis and Verbena cubits, Salvia Nemorosa and cultivars, and hylotelephiums (formerly sedums). Plants with storage organs in their roots – such as dahlias, with their fat tubers, or daylilies such as Hemerocallis “Hyperion”, with thick underground rhizomes – might fare well. See also comfrey, mallows, poppies and wild carrots – anything wielding deep taproots.

One of the reasons why perennial vegetables tend to be fair better than annual vegetables in extreme weather is because they have extensive, mature root systems that allow them to reach down into the soil where more moisture might be hidden, but also draw back resources and wait it out. They might look a little beaten, but with the first rain they will start to bounce back.

Study your garden for answers

Woman planting broad beans in a raised bed
Diverse planting can protect your crops. Photograph: Chris J Price/Getty Images

Take a good look around your garden and pay attention to what did and didn’t do so well, to see if you can rectify the conditions. Was it drying winds or lack of shade? Could you grow taller plants to offer shade and slow down whipping winds? Sunflowers (not the super-tall ones that nearly always need staking) are a good example: they will offer shade to leafy vegetables and smaller plants and, if grown in drift or clump, rather than a single line, are very good at slowing down winds.

How you group plants also matters. A single line of annual vegetables have little to protect them; they are at the mercy of the sun and the wind. In block planting, the central members are fortified by their neighbors. Likewise, I have found that using polycultures instead of monocultures works, because of the diversity of planting. The lettuce out in the sun might bolt, but the one growing tucked under the courgette will be fine.

Leaf cover protects more than soil

Woman standing next to a sunflower patch
Sunflowers will offer shade to leafy vegetables. Photograph: Kanchanalak Chanthaphun/Getty Images/EyeEm

Exposed soil is baked soil, devoid of life. Most vegetables like to grow in soils around the 20C to 25C mark (as do many microbes, for that matter). Left to bake in the sun, soil can easily reach a temperature in the high 40s. Mulches can make a huge difference, but leaf cover does an even better job, whether that is specific ground cover plants, such as clovers and trefoils for the vegetable garden, or something as simple as leaving weeds in place before a hot spell.

Soil that is protected by leaf cover doesn’t just help the plants, but the wildlife, too: it offers refuges for insects, frogs, small mammals and birds. During the July heatwave, my resident blackbird spent the whole time hopping about under the dense leaf cover of my garden.

Mulching in spring and autumn, to protect the soil from summer suns and winter rains, has always been good practice. But temporary or short-lived summer mulches are going to become much more important. Straw mulches, grass clippings, alfalfa meal and comfrey leaves can also be used around plants that have high water requirements and bare soil, such as tomatoes, strawberries, courgettes, pumpkins, aubergine, mangetout and runner beans. Water these plants well, deep into the soil, when it is cooler, then cover with a mulch. Comfrey leaves are particularly useful, as they have the added bonus of feeding the plants as they break down.

Water wisely

Woman watering large sunflowers with a watering can
Water judiciously – and never on your lawn. Photograph: Dougal Waters/Getty Images

It makes sense to water anything that is still getting established, along with food crops, but do so late in the evening, very early in the morning or, if using a sprinkler, at night. Sprinklers use a huge amount of water, but if you can choose one that allows you to set it to sprinkle low to the ground, rather than up into the sky, you are at least not wasting it. Don’t ever water your lawn; it is wasteful. Grass has evolved to die right back at the surface and reappear again in autumn when the weather is cooler and wetter. You will notice that lawns that are cut longer are much more resilient than those shorn to an inch of their life.

Keep your soil well fed

Woman adding to compost heap
The organic matter in compost acts like a sponge in the soil. Photograph: coldsnowstorm/Getty Images

The single most significant thing you can do for your garden (after changing your bank) is to compost. It is an old idea – not quite as old as the soil in your garden; that took about 500 years to make – but it works. Organic matter acts like a sponge in the soil, soaking up water and releasing it slowly when it is needed.

You do not need to digit it into the soil; just spread it across a few centimeters thick and allow the worms to do the rest. They will efficiently move it down into the soil far better than you could. Their extensive network of tunnels will allow water and water to penetrate into the soil. In turn, this will feed the soil food-web, ignite the soil microbial community and encourage the roots to grow and explore.

An extensive and healthy root network is one of the best ways for a plant to become resilient. The better your soil, the better the root, the more they can cope with.

Two days of heat was hard; longer spells will be brutal. I stood for mer seconds in the afternoon of the last heatwave and watched the garden shimmer with that strange yellow light, anxious for the leafy things, but all I lost was a few lettuces. After years of composting and spreading it out, of not digging and planting my polyculture densely, the soil is resilient. Yours can be, too.

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