British gardens cover six million hectares of land and so, individually and collectively, garden owners can help to stem the trend of global decline in biodiversity. Sustainable design may sound restrictive, but if we unravel what the principles mean in practice, we can reveal boundless imaginative and practical solutions that allow for both wow-factor and eco-impact.

Green gardens make for a comfortable living space acting as a ‘heat sink’ by cooling and humidifying the surrounding air and absorbing greenhouse gases, air pollution and dust. Biodiversity goes hand-in-hand with a rich cultural mix that allows you to be expressive in your own style — complementing the architecture of your home and your lifestyle.

Water Conservation

The average house roof sheds 45,000 litres of rainwater per year — equivalent to perhaps 25 per cent of the water you consume. Diverting rainwater from the downpipes into a butt or underground tank is easy, but you will need to consider at the planning stage the uses to which harvested rain and grey water will be put.

  • If you’re not storing the water, slow the flow by draining it to the planting beds and deeper underground to mitigate against flash flooding.
  • Use rain chains to direct water from roofs and canopies — they’re entrancing to look at, and children love them.
  • At ground level, there is a growing selection of permeable and porous products for paving.
  • Ensure that the fall on impermeable surfaces inclines towards flower beds, a swale or a rain garden.
  • Instead of impermeable paving, cover grass with vehicle-bearing grills for access and parking.
  • Avoid upstands that kerb the flow.
  • Think twice before installing any planters or raised beds that will require intensive irrigation.

Dealing with Drought

You also need to plan for extended periods of drought. Follow the ‘right plant, right place’ rule — getting the synergy between hard and soft landscaping, and understanding your soil. You can also prevent moisture loss through evaporation by mulching your planting beds. You can use organic compost, chipped bark, various decorative aggregates, or even crushed seashells.

Choosing Plants for Biodiversity

In designing the garden, marrying the cultivated with the wild needn’t be a contradiction. There are many examples of crisply planned gardens using beneficial plants that are productive and wildlife friendly.

Espaliered fruit trees framing a path, multi-stemmed amelanchier planted in a grid formation, or a living wall of ivy can all be beneficial to wildlife.

  • Why not screen part of the garden with a clipped hedge or battened panel to create a wilder area for bug hotels, compost, log piles and nectar-rich planting? Children can use this as a chance to go bug hunting and learn about insects.

Green, Brown and Sedum Roofs

Another means of making your site as biodiverse as possible is by establishing a green roof, which will also increase water retention. Several living mats of plants are available, which simply roll out onto a roof with a gentle pitch. Commonly, sedum blankets are used, however a mix of species, including sedum and a range of wildflowers, will generate greater biodiversity and visual interest.

An alternative is a ‘brown’ roof, which is composed of rubble or other aggregate. This can be left to the vagaries of seeds dropped by passing birds or the wind, or sown with a wildflower seed mix. The loadbearing capacity of your building will determine the depth of growing medium and, consequently, which plants are sustainable in that micro system.

A permeable garden

Choosing Sustainable Wood

Decking is relatively light in weight, so is often ideal for balconies and roof gardens. A deck can bridge over conduits and between different levels of the garden. It provides wheelchair-friendly access over marshy ground and minimises disturbance to tree roots.

  • Budget permitting, you can flaunt the beautiful grain and colour of hardwoods like ipê and eucalyptus for seamless flooring that extends the house into an outdoor room.

Timber is being grown, processed and assembled faster than in the past, and with more durable and sustainable results. A modified softwood, such as an impregnated yellow pine from the southern United States, or a heat-treated redwood from Scandinavia, is likely to perform better than a cheap tropical hardwood.

You need to look beyond seductive brochures and dreamy descriptions to find the facts. In so doing, take care that one eco-positive feature (e.g. low-energy production) isn’t counteracted by a negative (e.g. reducing the life expectancy of the board because you’ve selected the wrong one for the job).

In the UK, almost all decking timber is imported. The few exceptions are limited quantities of green oak and sweet chestnut — though these are often better suited to cladding, fencing and pergolas than boardwalks. The precise origins of a board can be difficult to trace.

  • The magic tickets for responsibly sourced timber are the Forest Stewardship Council and the Programme for the Endorsement of Forest Certification (PEFC) — though some countries operate under different schemes. Top-of-the-tropical range ipê from Brazil is subject to the IBAMA code of practice.

Responsible sourcing is not just about forestry but the complete lifecycle, including the production processes and our own environmental impact as consumers. Wood waste, for example, is an efficient means of powering sawmills. While chemically treated timber offcuts have to go to landfill (they give off toxic fumes if burned on an open fire), untreated woods can safely be used in a woodburning stove.

Sarah Eberle's ‘Garden for Monaco’ at the Royal Horticultural Society Chelsea Flower Show, 2011

Image: Garden For Monaco by Sarah Eberle

Sarah Eberle selected eucalyptus for her ‘Garden for Monaco’ at the Royal Horticultural Society Chelsea Flower Show in 2011. Environmental credentials were essential to the design, as the Principality of Monaco wanted to show the world it’s no longer all James Bond and casinos. Sarah needed timber that “was sustainable and met a high-quality specification”. It had to be smart, strong and stable enough to work inside and out for the decking, fascias and a cantilevered staircase. “What made me happy about eucalyptus is that we can grow it almost anywhere — and it’s easy to crop,” she says. New generations of plantation-grown eucalypts can be harvested in 14–16 years, compared to 60 years plus for many other tropical trees.

Reclaim, Recycle and Reuse

Aim to reclaim and reuse as much material as you can. This goes for mulch and compost as much as paving and other building materials. To lessen the carbon footprint, reduce waste costs and potentially economise on labour time, you could hire a Rhino machine. This will crunch up broken bricks and pavers, lumps of concrete and offcuts of stone into an open-grade hardcore.

Consider too the salvaging opportunities for generations to come. Specify lime mortar (instead of cement mortar, which is far harder and difficult to clean off) for constructing your garden — it will be easier to take the wall or paving apart and reuse the materials in the future. Lime mortared joints are also more sustainable as they allow some natural flex in the wall to cope with extremes of wet, dry, hot and cold.

Don’t forget, for both house and garden builds, make sure mortar mix isn’t leeched into the soil by sluicing out buckets into flower beds — as this can dramatically alter the pH of the soil and cause damage to plants that thrive in neutral or more acidic conditions.

Essential Checklist

  • Work the space to your best advantage; consider productive gardening by mixing edible crops with decorative plants
  • Make best use of existing assets — for example, established trees and ponds
  • Enhance biodiversity wherever possible
  • Minimise inputs and outputs, ensuring that finite natural resources are preserved
  • Follow SUDS (Sustainable Urban Drainage Solution) principles in relation to rainwater
  • Plant for posterity
  • Source materials responsibly and from local suppliers wherever possible
  • Reclaim and reuse
  • Apply ecologically sound practice on site, in groundwork preparation, building, garden cultivation and maintenance

Further information:

Featured image by Martin Looker

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