Green technologies - Gardens With a Conscience - Garden Design (2015)

Garden Design (2015)

Gardens With a Conscience

Green technologies

PLANTED ROOFS AND WALLS help to insulate buildings and attract wildlife, while choosing solar-powered items reduces our dependence on fossil fuels.


Although an ancient technique, covering roofs with plants is enjoying a resurgence of interest, fuelled by the need to increase or conserve biodiversity, slow rainwater runoff, insulate buildings, and create a social space, as well as providing visual interest. Before you start, consider what you want to achieve from your roof garden, as this will determine the approach and cost. While greening the roof of a small shed can be a simple DIY project, larger schemes will need the services of a specialist contractor. Planning permission may be required, especially on period or listed properties, and a qualified engineer will also need to assess the load-bearing capacity of the building.

To flourish, green roof plants must have sunlight, moisture, drainage, nutrients and aeration, and if any factors are lacking or the species chosen are inappropriate for the conditions, the scheme is likely to fail. Green roofs vary from ‘lightweight extensive’, usually involving pre-grown mats of drought-tolerant, hardy succulents, such as sedum, through to ‘intensive’, with more than 200mm (8in) of substrate and bespoke planting designed to meet the site conditions. Most extensive and many intensive green roofs are supplied as complete systems from specialists.

“The best plants for sunny roofs are sedums, which are drought- and wind-tolerent - just don’t over water them. Low-growing alliums also work well. For shady sites, try Polypodium vulgare and Sedum ellacombianum.”



An option for lights, pumps and other small accessories, solar-powered features are inexpensive, easy to install and increasingly sophisticated in design and style. Units are either driven directly from a solar panel or via rechargeable batteries, and to work efficiently, they need constant direct light. If units are set in shadier sites, the running times will be short or the power source too low.

Lighting units vary from small, glowing pathway markers to patio and security lights that use LED bulbs, although these lights are not as powerful as fluorescent or halogen types. Solar power is also used for water features and fountains, either driving the pump directly, meaning it cannot run at night, or via a battery for greater flexibility. Water flow is not as powerful as that from a mains-driven pump, but usually sufficient for ripple effects or low jets.


Methods of covering vertical structures with plants involve two basic approaches, namely green façades and living walls. Green façades involve climbing plants growing on a vertical structure. Their stems may require supports, such as stainless steel or wooden trellis, meshwork, or cabling, or you can opt for self-supporting climbers, such as Boston ivy and climbing hydrangea. Green façades can be used to provide privacy or security, or to screen or embellish parking lots, patios, walkways or sitting areas. Plants are generally rooted in beds at the base of the structure, or in self-contained planters, also known as ‘living curtains’ or ‘green screens’. Depending on climate, choice of species and growing conditions, green façades may take several seasons to achieve maturity.

Living wall systems or ‘vertical gardens’, as they are sometimes known, are composed of panels, modules, or bags, usually attached to a wall or free-standing framework (see page 65), which hold non-climbing plants, rather like a series of windowboxes. Modules are variously made of plastic, polystyrene, synthetic fabric, or clay, and can support a great diversity of plants. Flowers, herbs, vegetables and fruit often feature in living walls, planted in a range of compost types, including coir, crushed bark, expanded clay granules, gravel, and perlite, often in blended mixes. Watering and feeding systems are essential for the plants’ long-term survival, with computer controlled units providing the best solution for large installations.


This simple modular system by Vertigarden offers the home gardener an easy option for a small green wall.


Ideal for garden rooms, pavilions and sheds, planted roofs help to help control the flow of water into drains and increase wildlife habitats for insects and birds.


Solar panels can be used to power garden equipment and facilities, such as lighting and water features. Improvements in technology will continue to increase their effectiveness.


Solar-powered lighting can be installed in every type of garden and located wherever needed, as long as the units that absorb energy are positioned in a sunny area.