In some gardens and parks there are healthy, lush leafy rhododendrons. It turns green. They grow and thrive but do not bloom. Finding the cause is not always easy, even for gardeners and botanists. Some of the most common reasons why rhododendrons do not flower:
- lack of light
- Incorrect fertilization
- Wrong pruning
- pests or diseases
- Seedling propagated plants
- Buds open prematurely
Flowering strike due to lack of light
Even rhododendrons go on flowering strike due to lack of light. If rhododendrons are completely in the shade, they use up all their energy to create enough leaf area to use the few rays of sunshine. In doing so, they reduce flowering.
What to do? Move the plant to a sunnier location in autumn or ensure more light by cutting back and thinning out the crown of the tree.
Incorrect fertilization
Too much good food not only makes us humans, but also the rhododendron fat and flowering lazy. Over-fertilization with nitrogen and phosphorus reduces flowering. Both active ingredients activate growth and leaf formation while phosphorus contributes to flower formation.
What to do? Use pure nitrogen fertilizer in organic form if possible (cattle manure (€18.80) or horn shavings) to avoid one-sided fertilization. Match nutrients to the soil.
Wrong pruning
Rhododendrons form their flower buds in the previous year. If you cut them back before flowering, you will miss out on the blaze of color for a season. You can only cut back late-flowering rhododendron varieties such as Cunningham's White in spring.
pests or diseases
An infestation of the flower buds by rhododendron cicadas in May can destroy the blooms.
What to do? Fight insects with insecticides by the end of May, remove all infested flowers early and dispose of them with household waste.
Seedling propagated rhododendron
Propagating rhododendrons from seedlings means waiting years for the first bloom. Vegetatively propagated cuttings or grafts flower after just one or two.
What to do? When buying rhododendrons, look for grafted specimens!
Buds open prematurely
During a period of warm weather in winter, the buds open prematurely and freeze before they bloom. In any case, the following normal flowering is lost. Diseases can also occur before the buds open.
tips and tricks
When you replant or move a rhododendron, most of the time it will not bud. Then it will not bloom the following year. It can also happen that it stops flowering from time to time when it is young or that what are supposed to be flower buds are larger leaf buds.