Magnolias are magnificent, slow to moderate growing, large size evergreen and deciduous trees ideally suited for use as a specimen tree, or as part of a group planting screen. Their large glossy green leaves and profuse display of spring flowers make them a popular ornamental tree in the UK. If winter temperatures drop between 10 to negative 15 degrees Celsius, damage or mortality can occur.
Culture for Magnolia
Magnolia grows optimally in acidic (pH 5.0 to 6.0) well drained, loamy, moist, rich soils. They are tolerant of high soil moisture but cannot withstand prolonged waterlogging. Partial shade or full sun is ideal. Irrigation is essential in times of drought.
Concerns about Magnolia
Monitored for scale attack on twigs. An indication of a heavy scale infestation is a blackening of the leaves or twig dieback. Bleaching of the leaves may be caused by thrips or mites. Occasionally caterpillars, whitefly, and mealybugs are found damaging trees . Numerous fungal leaf spots attack magnolia. Armillaria can weaken the trunk and roots of magnolia. Verticillium wilt is a fungal disease which infects the root system and is seen as dieback of branches.
Management Practices for Magnolia
Regularly inspect for Armillaria. Treat if detected (air spade, Trichoderma, phosphite, mulch). Apply 3 to 4 insecticide and/or fungicide sprays mid April to late May to suppress pests and diseases. Apply fertilisers and soil treatments based on soil test results ideally in spring or autumn. Magnolia are susceptible to iron and nitrogen deficiency. Inspect for animal damage, especially squirrels in winter and apply repellent to tree trunk and branches in spring.