I LOVE stewartias. I have many, including many different species.
My nephew recently bought a new house and wanted suggestion for a tree,
so naturally my wife and I bought him a beautiful stewartia pseudocamellia.
It came from a local reputable nursery and has a two year warranty.
It was planted last summer after the normal bloom time,
so this summer was it's first opportunity for bloom.
The tree looks healthy and happy. But the blooms aren't developing properly.
The blossoms look 'pinched off' before they open.
We had a torrential rain about the time the buds were nearly opening,
but it doesn't look like a mechanical injury to me.
What's wrong with his tree? Is it an infection? Foliage looks fine.
Meanwhile, my trees are all blooming beautifully (10 miles away).
You better disinfect yourself before you go home...
I have only heard of this malady one other time - from a lovely woman who has gardened in suburban Baltimore her whole septuagenarian life, on wonderfully acid loamy soils. Stewartia sp. have continued to defy her, with this unsatisfactory blooming condition happening to her annually.
If no other reference resources were available, I'd say write/email the Polly Hill Arboretum on Martha's Vineyard (West Tisbury, MA - http://www.pollyhillarboretum.org/ ). They are one of - if not the - pre-eminent cultivators and researchers of the genus Stewartia, and the plants grow there like nobody's business. Imagine having to have interns weeding out seedlings of Stewartia because they are too prolific...
Guessing with no other information, I'd bet it is either fungal or bacterial infection. If known and treated preventatively instead of symptomatically (that is, before it is apparent rather than after the fact), I bet you could likely eliminate the problem from this landscape.
If you do contact them and get some answers, I'd love to see them here. I have a great Stewartia that sometimes loses blooms in this manner. I live in the rainy, soggy Pacific Northwest, so the tree gets drizzled on all spring. I have always assumed that the continued wet leads to a bacterial infection, but I'd love to have real information.
You (or your nephew) should use your Cooperative Extension Service's diagnostic testing capabilities to determine what this pathogen is. Collect some of those affected plant parts, and follow the reporting process.
Consulting Sinclair & Lyon's Diseases of Trees and Shrubs, 2nd Edition, I only see Botrytis cinerea referenced as affecting Stewartia sp. - but that could very well be it.
Wet humid weather conditions are exactly what Botrytis blight likes. Please keep us posted on what you find out.
Wow, thanks for the info, though not quite as optimistic as I was hoping for.
I'll contact both organizations to get their feedback.
We have had an unusually wet and cool (for us) spring/early summer.
Continues to be cool and drippy even into July, which is really unusual for us.
I'll post whatever info I get.
Thanks again for the info.
I think it's a temperature change right at bloom set time. I enjoyed a very large collection of Stewartia at UBC Botanical Garden today and they went through a very wet and cool June. Bloomin' like mad.