Poor soil conditions don’t necessarily mean a poor garden. Turn your wasteland of rubble into a pretty paradise
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Gardeners are constantly exhorted to improve their soil conditions, to add lime, well-rotted compost and manure, to water in the evening, to do this, do that… all to give their plants their best life.
That’s all very well in the good times but how are these pampered plants going to cope in the bad? When the rains fail to come? Or when they do come and come and come and the soil conditions are ruined and water-logged. Not only do such pampered plants lack resilience, but when you pamper your plants, you will also be pampering your weeds.
Welcome to the poor soil garden where plants have to struggle to survive. Where they will be shorter and sturdier than their coddled cousins, and more drought and deluge-proof.
This type of cultivation has been around for millennia but is only now gaining traction in 21st-century gardening practices. And it is great news for those gardeners battling difficult soil conditions, say on the site of a demolition where building materials have been dumped after a new-build, or where an old drive was. Even those with merely sandy or heavy soil can now find relief from the endless quest for “perfect” growing conditions. It is also great news for the environment, not just because these gardens require less and even no water, but because they can save truckloads of old building materials from going to the dump.
Perfectly suited to sub-optimal conditions, these are gardens in which the main growing media are free-draining materials such as gravel, ground glass, crushed and pulverised concrete (all of which can be bought from landscaping supplies), rubble, old bricks, plasterboard even. There is no need for compost, manure or fertiliser. Once established, there is no need for watering either, rainfall alone will be enough. A quick look around any urban environment – in a crack in the footpath, where a building meets the tarseal, in a dusty shingle carpark – will reveal just how tough plants can be as they grow in these seemingly hostile and unlikely environments.
Fear not, however, your poor soil garden will look like these. Should you desire, in time it could resemble a traditional perennial garden – and for a fraction of the maintenance. If you prefer a more Mediterranean look, with plants popping up here and there in selected spots in the shingle, then that too can be arranged. Remember that a good proportion of the world’s plants grow naturally in less than favourable habitats – up a mountain, on river banks, in deserts, by the seashore, on cliffs, and those plants from more salubrious spots can often be induced to give up few “luxuries” in your garden for the good of the planet.
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How to create a garden in poor soil conditions
Spread out your rubble over the selected area, breaking up or burying any large pieces, then cover it with a thick layer of gravel. Plaster board can be used too, if crushed. Should you not have any rubble lying around, then buy it, in whatever proportions you chose, gravel or concrete aggregate (between 6mm to 9mm), river sand, or crushed glass.
Aim for the layer of the rubble and gravel to be about 7cm if the garden is on free-draining soil. Heavy clays will need a layer of at least 15cm to 20cm. The gravel acts as a mulch, sealing in water, absorbing the heat of the sun, protecting against frost and deters weeds.
Either plant into the soil or create a depression in the gravel, place a small amount of soil or compost in the bottom and insert plant, replacing all the stones. Water once, then in the ensuing weeks only water the individual plants when they look like they really need it. You want to be encouraging them to send down their roots to find moisture, thus becoming more drought-proof.
Once they are established no watering will be needed – except, perhaps, in times of extreme drought and you can’t bear the possible consequences.
Similarly, do not ever feed the plants; they need to learn to survive on very little. Their growth will be slower and, ultimately, they will be stouter but they will also be tougher. Some gardeners when planting into purely rubble and sand will remove any existing soil from a plant’s roots, believing the plant will thus quickly learn to seek out nutrients themselves.
Text Mary Lovell-Smith
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A little heartbreak is always involved in this type of gardening because it is only through trial and error that you discover which plants will survive the tough love and which will not. If a plant dies, resist the temptation to replace it with another of the same kind, even though this can be hard if it is a favourite.
The following plants are suitable candidates for poor-soil gardens.
Alyssum Annual or short-loved perennial. A pretty, sweet-smelling trailing groundcover available in a range of colours.
Calamintha Perennial. As its name suggests it has a sweet minty fragrance and dainty blue or white flowers.
Cornflowers Annual. An old favourite for a reason. Comes in a range of colours but the classic blue is almost unbeatable.
Echinops (Blue Globe or Globe Thistle) Perennial. This is a stunner with its bright blue architectural blooms.
Eryngium (Sea Holly) Perennial. This is another architectural blue stunner. Also available in white.
Gaura (Wandflower) Perennial. Tall slender stems support masses of starry white (sometimes pinkish) blooms.
Lychnis coronaria (Rose Campion) Perennial. The hot-pink form is gorgeous and worth seeking out. Self-seeds freely.
Nepeta (Catnips or Catmint) Perennial. It is loved by the felines, and also bees. Plus, it smells and looks fabulous.
Perovskia (Russian Sage) Perennial. It is the plant du jour for a good reason with its fragrant lacy foliage and blue flowers all summer long.
Santolina Perennial. Mounds of classy pale grey foliage are topped with unusual sunny yellow flowers.
Sedum spectabile Perennial. When most of the summer’s bloom are long gone these most attractive rose-pink flat heads are shining.
Achillea (Yarrow) Perennial. Its flat umbelliferous flower heads come in various colours and spell long hot summers with a capital S.
Aubrieta (False Rock Cress) Perennial. Its low-growing mounds are smothered in white, purple, blue or pink flowers.
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