Photinias are usually trouble-free, but can suffer from a number of common problems:
Photinia leaf spot (and heavy leaf loss)
This is considered to be a physiological problem (i.e. not caused by any pest or disease). The purple-brown spotting on the foliage is typical of a plant under stress. Recently planted semi-mature specimens are particularly prone, though many photinias are not fully hardy in the UK and any can suffer after cold, wet winters.
To avoid this type of damage, plant in a sheltered spot preferably against a wall or fence. Cold winds and/or frosty conditions can also damage foliage, again causing leaf spotting if adverse conditions are prolonged. Feeding with a general-purpose fertiliser such as Vitax Q4 or Growmore in spring or early summer should encourage healthy re-growth. If the ground is heavy, incorporate organic matter to aid with drainage.
The damaged foliage usually falls away naturally in spring/early summer, sometimes with heavy leaf losses. These losses are replaced by new growth in summer, but plants may become thinner in the centre and the only way to make them denser is to prune. Thankfully, photinias respond well to pruning, so cutting back some of the stems in early May/June will encourage younger, more leafy shoots.
- Purple blotching can also sometimes be a symptom of powdery mildew on photinia.
- Fireblight is more serious, but is unlikely to affect P. × fraseri cultivars such as 'Red Robin'. Occasionally, P. villosa and P. davidiana are affected.