We have several wild elderberry bushes. We have harvested the berries for over 20 years. Last year, two of the bushes produced almost no flower heads: in their place were ‘heads’ of very small leaves. The appearance is that the flowers were replaced by densely-packed, tiny green leaves; miniatures of the leaves found elsewhere on the plant. This year all the flower heads on those two plants were replaced this way. The plants are otherwise quite healthy-looking. The remaining bushes are all normal and have produced fruit. Nothing has been done differently.
What is causing this? Is there something we can do to help the plants revert to producing flowers? Should we simply remove the affected plants?
Elaine Johnson firstname.lastname@example.org 22/08/19 416-532-2849
Leaf diseases can be a problem in wet weather but it doesn’t sound like any of the common diseases. A less common problem could be Eriophyid mites. They are too small to be seen by the naked eye and can cause leaves to roll up and turn brown. Spraying dormant oil early in the season can control the mites. See the following link to OMAFRA for relevant data on dormant oils. https://find.gov.on.ca/index.php?q=dormant+sprays+for+eriophid+mites&page=1&owner=omaf&lang=EN&Search.x=16&Search.y=18
Elderberries usually produce best on younger branches. Your shrubs are quite old and if they haven’t been regularly pruned, it could be that the branches are simply too old to continue flowering and producing fruit. Regular pruning will encourage fruiting and also remove any older growth that may be susceptible to attack by diseases and various pests. Try removing the affected parts and thinning out older growth. You may be interested in checking out another OMAFRA periodical about growing Elderberries : https://www.omafra.gov.on.ca/english/crops/facts/95-005.htm.
Also consider the location of the shrubs, Are they getting more crowded over the years? Lack of air movement can encourage spread of diseases. Maybe some overall trimming should be done on all of the shrubs. At the same time if you haven’t already done so, try adding compost around the base to provide nutrients. Healthy plants are better able to fight off diseases and pests.