Rhododendron yakushimanum Polaris

Plant Rhododendron yakushimanum Polaris in a semi-shaded position, sheltered from cold and drying winds, in moist, humus-rich, and light soil, with a tendency towards acidity (pH between 4.5 and 6). Like all ericaceous plants, it does not tolerate limestone soils, drought, heatwaves, or heavy soils saturated with water in winter. If the soil remains moist in summer, this rhododendron will also tolerate exposure to non-scorching sun.

Dig a hole three times larger than the pot volume. Soak the root ball in non-limestone water and plant the bush at the neck level, in a mixture composed of 1/4 peat, leaf compost, gravel or pumice, and loam. Water generously and keep the soil moist in summer. Azaleas and Rhododendrons have a shallow root system. Therefore, they are sensitive to long periods of drought. This is why humus-rich soil and abundant watering during dry periods are recommended. Additionally, this shallow root system is not very strong, hence it is essential to lighten heavy soils with draining materials (gravel, pumice, clay balls) at planting. Apply a mulch of crushed pine bark at the base of the bush every spring to retain soil moisture while maintaining an acidic pH.

Maintenance involves removing faded flowers in summer and removing dead branches. Azaleas and Rhododendrons can sometimes be attacked by vine weevils that eat the edges of the leaves and rootlets, as well as by the famous "rhododendron borer," which does not usually cause severe damage. Effective organic solutions are available today against vine weevils. Leaf yellowing (chlorosis) in Rhododendron indicates poor iron assimilation in the soil and leads to premature plant death. While limestone (from the soil or watering water) is often the cause, poorly drained soil or deeply planted root balls can also explain the phenomenon.