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2022-09-03 10:24:21 By : Ms. Helen H

Amid one of the driest summers in years, our gardening expert created a field of arid-loving species that flourish with minimal watering

When I became head gardener at West Dean Gardens, part of the West Dean College of Arts and Conservation near Chichester, in 2019, I had to try to fill two large pairs of shoes: those left by Jim Buckland and Sarah Wain, who had spent nearly 30 years shaping the near 100-acre site into the renowned horticultural gem it is today. One of my first tasks was to consider the gardening topics and future trends students would want to study – and an obvious contender was how to garden using less water.

With this in mind, we looked for a site that was very free-draining – and as the soil at West Dean is largely made up of gravel and alkaline loam over chalk, we had our pick of most of the garden. The edges of the site are already turned over to a more naturalistic style of gardening, but we found a central zone that seemed primed for something a little more “out there” horticulturally – possibly in need of a group of plants that were full of interest and colour.

So, we had our blank canvas – a free-draining site in an area that was sunbaked for most of the day – but the ground was flat and lacking in character. We started to play with the levels, looking to create ripples of planting across a plane of flowers. To reduce the risk of adding too much fertility, no soil was imported from other parts of the garden to create the new levels.

While this groundwork unfolded, we began to grow a number of drought-tolerant, perennial plants from seed. I needed large numbers of each plant to distribute throughout the site: this was not about groups of threes and fives but about pockets of plants, flowering across a large area. We wanted to give the impression of a naturally occurring meadow that had received the lightest of human touches, despite the backbreaking work that went into creating it. Ambitiously, we aimed for 100 of each plant to give us plenty of scope and choice of location across the site.

With a range of plants in small pots ready to go, we then began to discuss what to use as a mulch layer. We needed a good weed suppressant – with such a large area, we wanted to spend our time tweaking the planting and collecting seed, not chasing annual weeds around the site. George, one of my team, brought my attention to a study conducted by Ben O’Brien, an ecological landscape designer from Prince Edward County in Canada, who had experimented with growing drought-tolerant perennials using various stone mulches.

O’Brien had created a series of raised beds, using mixtures of recycled crushed concrete, sand and compost as a mulch, and then tracked the progress of the perennials within each bed. Those beds with pure, crushed concrete had very little weed growth but the plants grew slightly shorter compared with those grown in beds with a concrete, sand and compost mix.

The more compost and sand that was added to the mulch, the more weed growth – although the plant growth was also stronger as a result.

With this in mind, I took a trip down the road to our local recycling centre to source some recycled builder’s rubble. I wanted to see whether it would jar in the garden, from a visual point of view, having never thought of this material in terms of its aesthetic value before.

I was pleasantly surprised at how gravel-like the 40mm chips were and became intrigued by the notion of using a recycled, sustainable, local product. I decided to commit – and so we created a 10cm-deep layer across the dry meadow site. Each plant was spaced out at roughly 45cm in a random, matrix style to create a meadow effect, then planted through the recycled rubble. The top two thirds of the plant came in contact with the concrete and the bottom third in contact with the soil. To minimise weeds, every effort was made to avoid contaminating the stone mulch with the soil.

Planting took place in March and was followed by a single watering. No other watering has taken place since, which really highlights the moisture-retaining qualities of a stone mulch. We opened the dry meadow earlier this month and will use it to illustrate a one-day “Creating a drought-tolerant garden” course in October.

Knepp Castle in West Sussex has recently transformed its 1.3 acre walled garden to follow the ethos of the wider estate, which is now renowned for its trailblazing rewilding project, as described by owner Isabella Tree in her bestselling book Wilding.

The aim at Knepp is to create a horticultural experiment in maximising biodiversity that will create opportunities for learning and inspiration using a community of drought-tolerant, wildlife-benefiting plants.

“The Knepp approach was much more about reducing soil fertility than about retaining moisture,” says Chelsea gold-winning designer Tom Stuart-Smith, one of the masterminds behind the project. “We started from the premise of wanting to create as many habitats as possible out of a flat site, so the two main things we could manipulate were aspect and soil. At its most extreme we have about 20cm of crushed concrete and sand over subsoil, raised up on mounds to improve drainage.

“People often fail to appreciate that it is winter wet not summer drought that is going to kill most of these highly drought-adapted plants. Also, it means we can get fabulous complexity in the vegetation with 10 species per square metre being, I would hope, perfectly sustainable – not possible in a highly fertile soil.”

This style of growing can be replicated in gardens big and small: creating a deep stone mulch layer and planting at the right time using deep-rooting plants can be adapted to suit lots of styles and soil types. But be aware of acidic soils as some recycled mulches will affect the pH, which can be difficult to reverse. Also ensure that planting is carried out in spring or autumn when there is plenty of moisture around; summer planting can be problematic and plants may struggle to establish.

Like the Knepp project, West Dean’s dry meadow is an experiment at this stage, but the initial results are very exciting. As I walk around the other gardens here at West Dean, parched by the hot weather, I am saddened by premature leaf fall on stressed trees, brown lawns and the generally lacklustre appearance of many plants. In contrast, the dry meadow is a joy to wander around: the plants are not just growing without rainfall but positively thriving – and they are awash with butterflies and bees.

Who knows what the winter weather has in store for us, but by propagating a few plants each year to replace any casualties, I am sure that this dynamic style of nurturing a plant community will go from strength to strength.

The cast members may change, but the enduring and highly relevant style of gardening using less water is here to stay and, once we’ve adapted to gardening with such limitations, why shouldn’t it be beautiful and great for wildlife too?

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