Annabelle hydrangea – flat flowerheads
Hi, I have an Annabelle Hydrangea. It appears very healthy with lots of growth but every year this Hydrangea gets leaf rollers (only plant affected in the area) and flower heads that emerge are flat like they stopped half way to becoming full developed balls. Even the flowerets do not fully emerge. The flowers look like Queen Anne’s Lace. I planted this bush 4 years ago and the first year it was fine but for the last 2 seasons I’ve had these deformed flower heads. Are the leaf rollers the problem or is there something else going on? I read the response on how to deal with the Leaf Rollers on Hydrangeas and will try to remove the affected leaves better this year. Last year I hand picked the insects off the plant.
Although Leaf Rollers are certainly an irritating pest, they do not cause the kind of change to flower heads that you describe. If you cleared up the plant debris under your hydrangea last summer and fall, you may find that you do not have as serious a Leaf Roller problem this year: hopefully you will have removed any pupating caterpillars you missed on the leaves. What you are doing to control them is the most efficient way to make sure that you rid yourself of them.
If your Annabelle bloomed normally and fully the first year, and produced a lacy bloom more recently, there are a couple of possibilities. The propagation of your Hydrangea arborescens ‘Annabelle’ may be an issue. Annabelle should be propagated from cuttings in order to be certain that the cultivar remains reliable over time and it does not revert to its “wild” source. A new stem emerging from the root, and not from the crown of the plant, may produce a flower that looks more like a “lacecap” – the typical Queen Anne’s Lace-like bloom of the wild species H. arborescens. For this reason, we are often advised to buy a hydrangea when it is in bloom. Can ‘Annabelle’ revert to its wild source? Here is an article in which one horticulturalist discusses a similar – and very interesting – question of reversion: https://web.extension.illinois.edu/askextension/thisQuestion.cfm?QuestionID=24686&catID=34&AskSiteID=34
If you left your seed heads on the plant throughout the winter (a really great idea) it is possible that your Annabelle produced seed that germinated under your existing plant. These new stems would produce the wild type of blooms you describe. Here is a website that has a couple of good photos showing the “wild” versus the true ‘Annabelle’: http://www.hydrangeashydrangeas.com/annabelle2.html
Finally, although unlikely from your description, here is a link to an article on Hydrangea Chlorotic Mottle Virus, a disease that produces distortion in blooms, with photos that you may use as a point of comparison: