Best plants for hot south-facing walls

A south-facing wall in the northern hemisphere is one of the hottest spots in any garden. The wall absorbs solar radiation all day, reradiates heat through the afternoon, and creates a microclimate that may be 10–15°F warmer than air temperature at the same site. This is a liability for most plants.

A south-facing wall in the northern hemisphere is one of the hottest spots in any garden. The wall absorbs solar radiation all day, reradiates heat through the afternoon, and creates a microclimate that may be 10–15°F warmer than air temperature at the same site. This is a liability for most plants and an asset for heat-loving species adapted to Mediterranean or subtropical conditions.

Per Penn State Extension, south-facing wall microclimates in zones 5–6 can effectively approximate zone 7 or 8 conditions for heat-sensitive species, extending what can be grown. The trade-off: these locations are also frequently the driest in the garden, as the wall blocks rainfall from the west and reflected heat accelerates evaporation.

Wall espalier vs. border planting

Per Penn State Extension, wall espalier — training a tree or shrub against a wall in a flat, two-dimensional framework — maximizes the microclimate benefit while minimizing space. South-facing walls are ideal for espalier fruit trees that need heat accumulation. Freestanding border plants near a south wall will benefit from reflected heat but also need wind and drought tolerance.

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