Balcony gardens make their debut at RHS Hampton Court Palace Garden Festival
Cats, a retreat and a space about how to use grey water feature in the debut Balcony Gardens installation at RHS Hampton 2025
A popular feature at RHS Chelsea Flower Show, the Balcony Gardens are coming to RHS Hampton Court Garden Festival as installationsthis year. Packed with small space ideas, they aim to bring gardens to everyone, with tips and inspiration which could also be applied to roof tops, front gardens and windowboxes. This year’s spaces bring us a garden for cats, a retreat and a space that teaches us about our water usage.
Whiskers and Wildflowers designed by Elisabeth Wright-McCalla
Whiskers and Wildflowers is designed to be a feline paradise and sanctuary for both cats and people. Raised planters let cats climb through grasses, while trees provide height and dappled shade. Filled with beneficial plants, it’s a shared retreat of calm, health, and curiosity.
A Quiet Retreat is designed for those who work from home, providing a sensory retreat for mental grounding and mindfulness. Warm-coloured flowers and textured foliage create a nurturing environment, while natural materials – clay, timber and woven surfaces – enhance the tactile experience. Seating invites daily pause and reflection.
One Element designed by Nadine Charlton and Michael Lote
The One Element Balcony Garden aims to demonstrate how grey water can be used in a domestic setting for horticultural purposes and provide an opportunity for the public and also industry professionals to experience this in a different way. Inspirational and thought-provoking, it includes many aspects that can be adopted within gardens and homes across the UK and shows what can be achieved while preserving our natural resources.
The One Element plant list
Trees and shrubs
Hedera helix 'Arborescens’(Tree ivy) Morus nigra (Black mulberry) Physocarpus opulifolius 'Diabolo’(Common ninebark) Salix alba (White willow) Salix rosmarinifolia (Rosemary leaved willow) Taxus baccata (Yew) Wisteria brachybotrys f. albiflora 'Shiro-kapitan’(Silky wisteria)
RHS Head of Sustainability Malcolm Anderson provides insight into how we can be more sustainable in our use of grey water and how we could have baths and showers in our gardens.
An hour of watering with a hose can use as much water as a person uses in a week. We know how bad single use materials are for the planet, and we now need to consider eliminating single-use water. Garden watering can increase peak demand on water supply systems by 50% when the weather is hot and dry. Reducing our water usage would eliminate the peak demand and also save the carbon associated with pumping and treating the water before and after it reaches our homes.
Did you know...
A 4-minute shower at 9 litres per minute would give you 36 litres of water in the bath. With a daily shower, that’s enough water (252 litres in a week) to irrigate an area of around 10 m2 with 25 mm of irrigation every week, which should easily see you through a hot dry spell. A bath of 80 litres every day would use 560 litres in a week.
When it comes to soaps, in theory, liquid soaps made with potassium salts rather than the typical sodium salts should work better for plants. Potassium is a plant nutrient, and roots really don’t grow well with too much sodium. However, the RHS isn’t aware of any soaps that have been tested in this way. The key thing is to keep the amount you use to a minimum. You could also have a go at making your own soaps.
You could collect outside water in a bath. In a 10mm rain shower you would be able to collect 7.5 litres water directly into the bath (if you leave the plug in). It would be worth doing this so the plants can rotate between having some fresh rainwater before you shower again.
How do the plants clean the water? The substrate they are growing in is free draining, so it stays well aerated, which means roots are provided with enough oxygen to promote healthy growth. This can be done by ensuring that the soil is well-draining and not waterlogged, or by adding organic matter to the soil to improve its structure and allow for better air circulation. Being well
Aerating means providing roots with enough oxygen to promote healthy growth. This can be done by ensuring that the soil is well-draining and not waterlogged, or by adding organic matter to the soil to improve its structure and allow for better air circulation. Aerating a lawn means creating small holes in the soil to allow air, water and nutrients to penetrate the roots of the grass.
aerated means that bacteria and fungi within the soil can thrive, which then eat the detergents, skin and sweat.
To grow well, plants need a wide range of
To grow well, plants need a wide range of nutrients in various amounts, depending on the individual plant and its stage of growth. The three key plant nutrients usually derived from soil are nitrogen, phosphorus and potassium, while carbon, oxygen and hydrogen are absorbed from the air. Other vital soil nutrients include magnesium, calcium and sulphur. Most garden soils contain enough nutrients to promote healthy plant growth.
nutrients in various amounts, depending on the individual plant and its stage of growth. The three key plant nutrients usually derived from soil are nitrogen, phosphorus and potassium, while carbon, oxygen and hydrogen are absorbed from the air. Other vital soil nutrients include magnesium, calcium and sulphur. Most garden soils contain enough nutrients to promote healthy plant growth. Nutrients such as the phosphate, potassium and nitrogen are taken up by the plants, leaving clean, but not drinkable water for the remaining garden irrigation.
The One Element Balcony features willow trees (Salix). Salix is a high water-use species as it typically grows close to water and in wet soil. It can reduce infiltration to groundwater depending on the rainfall rates, soil depth and number of trees. Salix varieties have been used to design zero-discharge sewage treatment facilities, in nitrate-vulnerable zones where all the waste water is evapotranspired and the nutrients are harvested in the willow but, all that water evaporating will help to keep us cool in a heatwave.
We know not everyone has a private enough space to bath or shower outside, but with the increasing risk of hosepipe bans across the UK, finding a way to easily use grey water will become increasingly important.
The Royal Horticultural Society is the UK’s leading gardening charity. We aim to enrich everyone’s life through plants, and make the UK a greener and more beautiful place.
