“A Popular Feature Tree”
Native to Japan and parts of Asia, Japanese maple (Acer palmatum) has been cultivated in temperate areas around the world since the 1800s. This tree is one of the most common features in landscapes of the Pacific northwest and British Columbia. There are many varieties with differences in leaf color, leaf shape, growth habit, and bark appearance.
- Performs best in well-drained but moist organic soil, at slightly acidic pH.
- Variable by species, but often suffers from leaf margin scorching in full sun locations.
- Deep shade will cause colored foliage to revert back to green.
- Shallow roots will benefit from mulch to reduce soil temperature and moisture fluctuations.
- Verticillium wilt is the most common and lethal pathogen of this species.
- Phytophthora root rot and anthracnose foliar disease, defoliating caterpillars, and leaf feeding beetles are also common health issues.
- Like many maples, prone to formation of girdling roots which can slowly lead to dieback and mortality.
- Early season aphid infestations also occur.
- Armillaria is also known to cause decline and death of this species.
- Stressed plants may be attacked by ambrosia beetles.
Bartlett Management Practices
- There is no direct treatment for verticillium wilt, but potassium phosphite soil treatments will help prevent infection and slow decline in infected plants.
- Expose root collars and inspect for/remove any girdling roots.
- Mature specimen should be pruned so that the unique branching architecture is visible.
- When soil organic matter level is less than 5%, add mulch and organic matter.
- Treat preventatively against ambrosia beetles when plants are stressed.