Keeping gardens and outdoor living spaces cool and comfortable over summer is a key consideration for many homeowners – and will likely become a greater priority as temperatures rise. In this article, we explore how a well-planned landscape can minimise heat islands and create cool microclimates in Kiwis’ back yards.
Here are some of the most effective strategies landscapers have shared with NZ Landscaper Magazine to achieve heat-resistant gardens for their clients.
Choose the right plants
• Shade trees: Temperatures under shade trees can be as much as 10-25°C cooler than unshaded areas, depending on the ground covering underneath, while planting trees so their shade covers part of the home can reduce temperatures inside. Deciduous trees are ideal, as they provide shade in the summer and let sunlight and heat through in the winter.
• Shrubs and ground covers: Shrubs and ground covers help reduce heat reflection from hard surfaces. Consider planting low-growing species to cover larger areas.
• Native plants: Native plants are naturally adapted to the local climate and require less water and maintenance. They can also create a more resilient and sustainable landscape over the long term.
Create cool climates
• Layered planting: Use a variety of plant heights to create layers of vegetation. This helps trap cool air and provides shade at different levels. Taller trees can provide canopy cover, while mid-height shrubs and ground covers cool the lower layers.
• Windbreaks: Plant windbreaks to direct cooling breezes toward the client’s home and garden. Strategically placed trees and shrubs can enhance natural airflow.
Implement sustainable irrigation practices
• Drip irrigation: Use drip irrigation systems to provide efficient and targeted watering. This reduces water waste and ensures plants receive the moisture they need without contributing to heat build-up.
• Mulching: Apply mulch around plants to retain soil moisture and keep roots cool. Organic mulches like wood chips, straw, or shredded leaves are effective and add nutrients to the soil as they decompose.
Reduce heat islands
• Minimise hardscapes: Hard surfaces like concrete and asphalt absorb and radiate heat. In urban areas, temperatures can be up to 7°C warmer than in rural areas. This is called the heat island effect. Minimise the use of these materials in your client’s landscape and opt for permeable alternatives like gravel, mulch, or permeable concrete to help lessen the heat island effect.
• Green roofs and walls: Green roofs and living walls can significantly reduce the heat island effect, as plants provide cover and naturally create humidity through transpiration throughout the day.
• Strategic planting: Plant trees and shrubs near hard surfaces to provide shade and reduce heat build-up. This is especially effective for driveways, patios, and sidewalks, and can help keep outdoor sitting areas cooler as well.
Use reflective and light-coloured materials
• Reflective surfaces: Use reflective materials for roofs, walls, and pavements to reduce heat absorption. Light-coloured paints and coatings can also help keep surfaces cooler.
• Shade structures: Install pergolas, awnings, and shade sails to provide additional shade and cooling. These structures can be covered with climbing plants such as wisteria or grapevines for added beauty and effectiveness.
Add water features
• Fountains and ponds: Water features such as fountains and ponds can help cool the air through evaporation. They also add a tranquil and relaxing element to a garden. Place them strategically to maximise their cooling effect.
• Rain gardens: Rain gardens are created by planting deep-rooted plants in a flat-bottomed dip designed to collect rainwater run-off from nearby hard surfaces. Planting this way helps the rainwater soak into the ground naturally. Rain gardens not only help reduce run-off and flooding during summer downpours but also cool the surrounding area as the rainwater soaks into the ground.
By implementing these strategies, you can create a landscape that keeps your client’s garden cool during the hot months and reduces the heat island effect. A thoughtful and sustainable approach to landscaping not only enhances outdoor spaces but also contributes to a healthier and more comfortable environment.