Rhododendrons comprise about 1,000 species of woody flowering plants of the family Ericaceae. They are famous for their attractive foliage and dainty flowers, and several species are cultivated as ornamentals. While these plants are relatively low-maintenance, they can still be prone to problems and diseases that could lead to sickness and death if not promptly addressed.
How to save a dying rhododendron
Whether or not you can save your dying rhododendron will depend on how much damage has already been done. However, the following general health care tips will ensure your best chance at doing so:
- Cut back overhanging parts, or transplant them if necessary.
- Reduce your use of nitrogen-rich fertilizer, since over-use could result in non-blooming buds.
- Practice mulching to protect the plants from freeze and thaw cycles during winter. Mulch over the root zone also helps retain moisture in the soil.
- Prune the plants well to prevent die-back.
- Check the leaves regularly for any discoloration, to ensure early diagnosis and control of pests or disease.
- Plant the dying plants higher in the ground to enable the roots to absorb nutrients more easily from the soil near the surface.
- Minimal cultivation should be done around the plants, because their shallow roots are susceptible to damage if this is not done with caution.
- Avoid overwatering the plants.
- Be sure to test the soil regularly for iron or magnesium deficiency.
- Position a shade-net to prevent sunburn, or transfer your plants to another spot if their current position is resulting in sunburn.
- Spray the plants with water in the evening to correct drooping leaves.
- Check the adequacy of the soil drainage and make amendments if necessary.
These plants need regular watering during summer when there is less rainfall. To promote vegetative growth, remove the dead flowers. Warp the plants with burlap in extremely cold temperatures, and apply extra mulch around the base of the plants during the fall season. Transplanting should be done during fall or early spring when the plants are dormant due to the cool temperatures.
Reasons your rhododendron plants may be dying
Rhododendrons become sickly and could die because of poor drainage and waterlogged soil. If the soil particles are too heavy or compacted, the roots will drown and root rot can set; the plants will not mature and will eventually die.
Wrong planting depth
Rhododendrons should not be planted too deep in the soil, since they have surface roots. Root balls should be at the soil surface; if they are buried too deep they will die. To ensure that the roots are able to breathe, be cautious about applying too much mulch on the soil’s surface. Replant ailing plants at a shallower depth if you suspect they may be planted too deep, and apply mulch over their root zone.
The variety is not hardy enough
The hardiness of the specific rhododendron variety may also play a role in whether it will survive in the area where you are growing it. If you are struggling to keep your plants alive, it may be a good idea to select hardier varieties.
Diseases and pests
Common diseases among rhododendrons include honey fungus and root rot. Pests such as vine weevils attack the stems, leaves and roots of the plants.
Early signs of a dying rhododendron
Rhododendrons that are magnesium-deficient tend to develop yellowing leaf tissue between green veins, especially among older plants. If the leaves are yellowing on younger plants, it could be that the soil is too alkaline for the plants. Fix this issue by spraying iron sulfate around the plants, or adjusting the soil pH to make it more acidic.
Brown spots on the leaves
Brown spots can be caused by fungi and humid summer temperatures. To fix this, cut or trim a few branches to prevent overcrowding, and treat the plants with fungicides.
Buds fail to open
Buds turn black and die before opening because of a fungal infection called bud blast. To fix this, increase the humidity around the plants and place them in areas where there is sufficient sunlight.
Leaves can curl up, especially during winter, when plants are trying to conserve water over the cold spell. If this happens during summer, it means that the plants are too dry. Water them immediately to prevent their leaves from curling and wilting, and to stop the dehydration doing any further damage.
Sudden wilting and death of stems
Fungi, such as the Phytophthora species, can cause stems to wilt and die. This type gets under the bark, causing stems to die in the middle of a healthy plant. Plants most at risk are those which have been weakened by late frost, drought, or over-exposure to the sun. The dead plant parts should be cut off and disposed of to prevent the spread of infection.
Rhododendron plant care
Take special care of your plants and mulch them every spring with two to five inches of pine bark chips or pine needles. This will protect the shallow roots and help retain moisture, since lack of water could reduce bud formation. Leave a few inches free of mulch around the trunks.
Fertilize rhododendrons sparingly and only when the flower buds swell during early spring, despite them being fall bloomers. The plants will get burned if you apply too much fertilizer.
Water your rhododendrons regularly, particularly during summer and if there is less than once inch of rainfall per week. Practise deadheading, and remove the dead flowers carefully. During the fall, wrap the plants with burlap and apply extra mulch around the base.
Rhododendron plants are popular for their spectacular blooms and attractive foliage. However, they are also prone to problems and diseases and may wilt and die if not treated promptly. Check the plants regularly for any leaf discoloration and avoid overwatering them to prevent root rot.
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