My Haaga set buds last year but never bloomed…outer edges of some of its leaves turned brown…..it appears to be doing the same this year…..it has been in that same spot and bloomed beautifully every year for the past 14 years until last year and now this year. Any idea what is going on with it?
Thank you for contacting Toronto Master Gardeners. Rhododendron x ‘Haaga’ is a hardy dwarf variety with stunning dark pink blooms. It is puzzling why your shrub hasn’t bloomed the past two years, as you mentioned it’s been in the same location for many years. Weather conditions are the typical cause of buds not blooming. A late frost or harsh winter winds could cause the buds to die and turn brown or black. The Missouri Botanical Garden has published a comprehensive guide on Rhododendron Care. An excerpt from this document:
“Cold Injury Dieback
In general, low temperatures can kill plants or cause various degrees of injury. Where freezing temperatures arrive early before the plants have sufficiently hardened off, even the most hardy rhododendrons and azaleas can be injured by the cold. The most common cold weather injury is loss of the flowers. While the external appearance of the flower buds is normal, cold temperatures will kill the immature tissues buried within the buds. Cutting the buds open will show a darkening of this tissue damaged by the cold. Low temperatures will also cause leaf scorch, leaf kill and stem dieback.”
The guide recommends: “Prevent cold injury by selecting hardy varieties, providing afternoon or partial shade, ensuring good soil drainage, fertilizing no later than July, fall watering when dry, protecting plants from drying winds and mulching.” Refer to the Missouri Botanical Garden’s guide for more detailed advice on watering, fertilization, soil acidity, pruning and winterization.
You should also give some thought to any changes in the growing conditions from year to year. Is there more / less sunlight in the area, has the soil acidity changed, is the shrub receiving the proper amount of water throughout the season? With some added attention and good weather conditions, hopefully your shrub will have many blooms next Spring.
June 10, 2024