Even during the warmest days of summer, heat alone only damages a few sensitive species. Extreme solar exposure, minimal humidity or insufficient soil moisture causes ‘Heat’ damage. Increased vascular activity during warm weather enhances sensitivity to such damage. Sun scald and foliar burn are the most common heat damage, but roots within containers may indirectly become damaged by solar exposure.

Most species that may be damaged by cambial sun scald of trunks and limbs are typically sufficiently foliated by mid summer to provide protective shade to sensitive parts. However, trunks of trees that have been improperly pruned or trees with narrow canopies lacking lower limbs may be detrimentally exposed. Such exposure is enhanced by reflective glare from pavement, walls, large windows and even parked cars and that tacky white ‘moonrock’. Of course some species are more sensitive than others are. For example, various species and cultivars of maple, cherry and apple are very sensitive, but pine, cypress and cedar are considerably more resilient.

Trunks of the orchard trees throughout the Santa Clara Valley were painted white for protection from solar exposure until foliar canopies could provide sufficient shade and bark had become striated. This is unfortunately unsightly in a garden. Although stakes in direct proximity to the trunks of young trees should not be necessary for support and may actually inhibit development of caliper (more on that topic later) they may provide protection from scald if tied ‘loosely’ to the south side of the trunk. Such stakes need not be large, but can be very effective if only ‘breaking up’ the exposure during mid day. Duct tape applied vertically to the trunk (not wrapped around it!) is also effective. (Do I use parenthesis excessively?)

Roots may be ‘cooked’ within inadequately insulated containers that are too exposed. Black vinyl cans that are used for nursery production are useful for their intended function, but become very warm if exposed and transfer the heat directly to contained media and roots. Heavier clay pots and wooden planter boxes are much better insulated and more appropriate for exposed areas. Of course any container may be used for specimens that are large enough to shade their roots or if the container is contained within a larger container.