Rhododendron Growing Problems in the Spring

Die-Back

• Die-back is a catchall term for several fungal diseases that may cause the death of the rhododendron. Typically appearing in late spring when the plant begins growing, die-back fungal spores live in the soil and develop as a result of poor cultural practices. Some of these include planting the rhododendron too deep or in soil that doesn’t drain adequately. Watering the rhododendron overhead in late afternoon or evening also promotes the disease. Prevent die-back by using a fungicide spray in late spring as the rhododendron begins active growth and reapply it in the summer, according to label instructions.

Leaf Scorch

• Foliage tends to dry out in cold, dry winter weather. Strong winds are especially brutal to the rhododendron. According to agents with the Cornell University extension, during the winter, the rhododendron’s roots are inactive so water loss can’t be replaced quickly enough. Then, in spring, during the first warm days, when the soil is still frozen, the leaves may become scorched at the tips. To prevent leaf scorch, give the soil a good soaking before it freezes and ensure the rhododendron doesn’t dry out during the growing season. Provide a windbreak and shade for the rhododendron to avoid excessive foliage drying and scorching.

Failure to Bloom

• When the rhododendron fails to bloom in late spring it may be due to a number of factors. If the plant isn’t properly hardened off in the fall – by withholding fertilizer and decreasing irrigation – the buds may freeze. If there is a sudden cold snap in spring after the buds break dormancy, they may die. Improper pruning in summer may also lead to failure to bloom in spring.

Leaf Gall

• Leaf gall is a fungal disease caused by various species in the Exobasidium genus. It occurs in early spring and causes distorted leaf and bud growth on the rhododendron. Leaves curl, become thickened and turn pale. Galls – which are swollen plant tissue -- go from being covered with a white, powdery substance to brown. Pick the galls from the rhododendron and dispose of them. This should clear up the problem. If it doesn’t, use a fungicide containing mancozeb or copper salts of fatty acids, according to label instructions.