Did you now that the presence of surfaces like glass, metal, rocks, and concrete can significantly affect the horticultural conditions by reflecting heat? Plants near heat-reflective surfaces need to be tolerant of heat heat and drought to thrive in such harsh conditions.

This article will briefly explain how reflective surfaces affect plant health and provide a palette of 5 plants that you can use instead of weaker plants.

The stones and pavers on this slope are reflecting an intense amount of heat. But they’re no match for Tasred™ Dianella tasmanica ‘TR20’ PVR. https://ozbreed.co.nz/plant-ranges/strappy-leaf-plants/tasred-dianella/

How Does Reflective Heat Alter Growing Conditions?

Increased Temperature

Reflective surfaces can cause a notable increase in temperature around plants. These surfaces can amplify the ambient heat, leading to conditions that exceed the optimal levels required for plant growth.

Heat Damage

Plants exposed to reflected heat may suffer from heat damage. This can manifest as leaf scorch, wilting, root dieback, and other forms of thermal injury. The intense heat essentially burns plant tissues, compromising their overall health.

Water Stress

Higher temperatures resulting from reflective surfaces can increase the rate of transpiration – the process by which plants release water vapour. This can lead to quicker soil evaporation, reducing the availability of water for plants and potentially causing water stress.

Stomatal Closure

Under extreme heat conditions, plants may close their stomata – the tiny pores on leaves – to conserve water. While this helps prevent water loss, it also reduces photosynthesis, thereby impeding plant growth compared with plants further from the reflected heat source.

Micro Climate Alteration

Reflective surfaces can create micro climates with higher temperatures compared to other areas of the garden. These micro climates make it challenging to maintain consistent growing conditions across the entire garden space.

Mitigating the Effects of Reflective Heat

To counteract the adverse effects of reflected heat, gardeners can employ several strategies:

   •     Mulching: Applying mulch around plants helps retain soil moisture and regulate soil temperature.

   •     Shading Structures: Installing shading structures can protect plants from excessive heat.

   •     Heat-Tolerant, Drought-Tolerant Varieties: Selecting plant varieties that are tolerant to high temperatures and dry conditions can ensure better survival and growth.

5 Plants for Near Reflective Heat Sources

These plants are ideal for near sources of reflective heat like rocks, pathways, glass and metal. Keep in mind that even resilient plants will slow down in harsh conditions, and so nearby plants of the same variety in better conditions will grow more quickly.

Plan accordingly and hide this fact with nearby companion plants of a different variety which won’t show the difference in growth rates.

Aussie Box™ Westringia hybrid ‘WES02’ PVR

Aussie Box™ Westringia is a versatile box hedge plant featuring mauve flowers and a dense growth habit. It offers an excellent alternative to English box plants, establishing faster, being more tolerant of heat, and requiring less water. This hardy plant can be pruned into a neat box hedge or left in its natural, compact ball shape. It has lower maintenance needs and is more drought-tolerant compared to other Westringias.

Size

   •     Pruned: 40-60 cm high x 40-60 cm wide

   •     Unpruned: 70-95 cm high x 70-95 cm wide

   •     Planting Density: 2-4 plants per square metre, 1.5-3 plants per linear metre

Care Instructions

• Position: Plant in full sun to light shade. Suitable for most soil types, but prefers well-draining soils. Avoid locations where the plant may have “wet feet” or be in depressed planting areas.
• Watering: Water as required for the first 8-13 weeks until the plant is established.
• Mulching: Use chunky mulch to help retain soil moisture and regulate temperature.
• Fertilising: If necessary, apply a slow-release fertiliser in the spring.
• Pruning: Leave in its natural shape or prune 1-3 times a year after flowering to maintain a tidy form. More frequent pruning will result in a neater appearance.
• Tolerance: The plant tolerates both frost and drought conditions.

https://ozbreed.co.nz/plant-ranges/shrubs-and-ground-covers/aussie-box-westringia/

Evergreen Baby™ Lomandra longifolia subsp. exilis ‘LM600’ PVR

Evergreen Baby™ Lomandra is a compact, fine-leaved, and evergreen strappy leaf plant known for its toughness. It’s both drought-tolerant and capable of handling periodic wet feet, making it suitable for positions other plants struggle in. This plant is roughly half the size of the popular Tanika™ Lomandra and features numerous golden flowers in spring. It’s also sterile and phytophthora resistant.

Size

   •     Height: 40-45 cm

   •     Width: 40 cm

   •     Planting Density: 4-8 plants per square metre, 2-4 plants per linear metre

Care Instructions

• Position: Suitable for full sun to part shade. It tolerates frost, drought, and periodic wet feet, thriving in soil types ranging from sandy loam to heavy clay.
• Watering: Water as required for the first 8-13 weeks until the plant is established. Occasional watering may be necessary during dry periods.
• Mulching: Plant in a well-mulched garden, using chunky mulch to retain moisture and regulate temperature.
• Fertilising: If needed, apply a slow-release fertiliser in the spring.
• Pruning: For optimal appearance, cut back 15 cm above the ground every 3-5 years. Regular pruning every 3 years is recommended but can be adjusted based on specific requirements.

https://ozbreed.co.nz/plant-ranges/strappy-leaf-plants/evergreen-baby-lomandra/

Better John™ Callistemon viminalis ‘LJ1’ PVR

Better John™ Callistemon is a superior variety bred from Little John. It has quicker establishment in the landscape, and features beautiful blue-green foliage and small red flowers that bloom from mid-spring to late spring. It’s also tolerant of drought and flooding.

Size

   •     Height: 60 cm – 1.2 m

   •     Width: 60 – 90 cm

   •     Planting Density: 3-5 plants per square metre, 1.5-2 plants per linear metre

Care Instructions

• Position: Plant in full sun to part shade. It suits sandy to heavy soils and tolerates both drought and cold conditions.
• Watering: Water as required for the first 8-13 weeks until the plant is established.
• Mulching: Use chunky mulch to help retain soil moisture and regulate temperature.
• Fertilising: Apply a slow-release fertiliser in the spring if necessary.
• Pruning: Prune every 3-4 years for a natural shape or every 2 years for a tidy hedge. Minimal pruning is generally required unless a specific form is desired.

https://ozbreed.co.nz/plant-ranges/shrubs-and-ground-covers/better-john-callistemon/

Revelation™ Dianella revoluta ‘DRG04’ PVR

Revelation™ Dianella is a medium-sized, strappy leaf plant with beautiful blue-green foliage and an abundance of stunning blue flowers that bloom from mid-spring through to early summer. This hardy plant spreads slightly and offers excellent erosion control capabilities, strengthening the soil by 135% according to a study conducted with Todd Layt and Ian Paananen in 2007. https://www.ozbreed.com.au/erosion-control-research/

Size

   •     Height: 50 cm

   •     Width: 50 cm

   •     Planting Density: 4-6 plants per square metre, 2-3 plants per linear metre

Care Instructions

• Position: Suitable for full sun to part shade. It tolerates drought and frost and is adaptable to sandy, sandy loam, and clay soil types. Avoid very poor soils. Can be planted in raised, flat, or depressed areas.
• Watering: Water as required for the first 8-13 weeks until the plant is established.
• Mulching: Plant in a well-mulched garden using chunky mulch to help retain moisture and regulate temperature. Ensure that the crown or base of the plant is not below soil or mulch level.
• Fertilising: If necessary, apply a slow-release fertiliser in the spring.
• Pruning: Revelation™ Dianella can be cut back 15 cm above the ground every 3-5 years if needed. Pruning every 3 years is recommended for optimal appearance, but this can be adjusted based on specific requirements.

https://ozbreed.co.nz/plant-ranges/strappy-leaf-plants/revelation-dianella/

Tanika™ Lomandra longifolia ‘LM300’ PVR

Tanika™ Lomandra is one of the toughest and most reliable landscape plants available for dry conditions. This evergreen plant boasts a compact, fine-leaf form and requires minimal maintenance. It produces small yellow flowers in the spring and has soft foliage that is gentle to touch, making it suitable for areas frequented by children.

Size

   •     Height: 70-90 cm

   •     Width: 70-90 cm

   •     Planting Density: 2-4 plants per square metre, 1-3 plants per linear metre

Care Instructions

• Position: Plant in full sun to moderate shade. It tolerates frost and drought and is suited to sandy, sandy loam, and clay soils provided they don’t experience periods of overly “wet feet.”
• Watering: Water as required for the first 8-13 weeks until the plant is established.
• Mulching: Use chunky mulch to help retain soil moisture and regulate temperature. Ensure that the crown or base of the plant isn’t below soil or mulch level.
• Fertilising: If necessary, apply a slow-release fertiliser in the spring.
• Pruning: Cut back to 15 cm above the ground every 3-10 years, depending on your aesthetic requirements. Pruning every 3 years will generally result in a better appearance.

https://ozbreed.co.nz/plant-ranges/strappy-leaf-plants/tanika-lomandra/

Conclusion

By removing sources of reflective heat and/or selecting appropriate plants, we can avoid struggling plants in our landscapes. Remember that differing conditions will always affect plants, so design your plant palettes accordingly.