Residential (home) gardens
A home garden is usually divided into zones: front (welcome, path, flowers), side (access, shade trees) and back (sitting, play, vegetables). Plant tall trees away from walls and pipes. Keep a clear path from the gate to the door.
Rooftop greening
A rooftop garden must be planned with care. The roof must be strong enough, because wet soil is heavy. From bottom to top the layers are: waterproof layer, drain layer, light soil, plants. Pick plants with shallow roots. Rooftop gardens also keep the building cooler.
Wall and indoor greening
Green walls use climbers on wires or panels filled with soil. They need little floor space, keep the wall cool and need a steady water supply.
Indoor plants need enough light, a pot with drain holes and not too much water. Place them near windows.
Other landscaping
Greenery can also go along roads (street trees), in school grounds, around factories, on car parks and in courtyards. The same rule applies: match plants to light, soil, water and use.
Key formulas and definitions
- Soil weight = area x thickness x density
- Roof layers (bottom to top): Waterproof, Drain, Soil, Plants
- Green cover (%) = green area / total area x 100
- Garden zones: front, side, back
Worked examples
1. A roof garden has 10 m2 of soil, 0.15 m thick. Soil density is 1200 kg per m3. Find the soil weight.
Volume = 10 x 0.15 = 1.5 m3. Weight = 1.5 x 1200 = 1800 kg.
2. Why is a waterproof layer needed on a roof garden?
Watering would otherwise leak through the roof into the building.
3. Give two reasons to plant a green wall.
It needs very little floor space and it keeps the wall and the rooms behind it cooler.
Common mistakes
- Putting heavy soil on a roof without checking its strength.
- Skipping the drain layer. Standing water rots roots and can leak.
- Planting a big tree close to a house wall or pipe.
- Giving indoor plants too much water or placing them in a dark corner.