Rowan or the European Mountain Ash is frequently planted as a street tree or a small medium sized garden for its showy clusters of white flowers in spring, followed by an excellent display of fruit that develop in clusters 10 to 12cm wide. Fruits begin maturing in August and stay on the tree through October. Mature fruit colour is usually bright orange with selected cultivars ranging from pink to red. Rowan grow to a height of 15 to 18m and can live beyond 100 years under favourable growing conditions.
Culture for Rowan
Rowan prefers a cool, rich loam soil, with good drainage. Full sun is needed for growth and development. Keep well watered during hot, dry periods. Not tolerant of prolonged drought or waterlogging. Ideal soil pH is 6.0 to 7.5.
Concerns about Rowan
Rowan are susceptible to fire blight, a devastating bacterial disease. Silver leaf and honey fungus can be problematic foliar and root diseases respectively. Pests include aphids, red spider mites, scale, and sawfly larvae. These insects often invade trees that are grown under stress. Susceptible to sun scald and sapsucker injury to the trunk.
Management Practices for Rowan
Regularly inspect for Armillaria. Treat (any time of year except if frost predicted) 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. For fireblight use a winter wash. Three sprays need to be applied from November to February.