Last weekend at the Mr Middleton Seminar day a lady brought me a sample and a question. It always helps when I get something to look at when trying to solve a problem and this was definitely the case with this mystery. The dahlia plant had been bought as a plant, not grown from seed, and it has never, ever flowered.
But it does try, and the buds are forming, but rather than being plump, they are narrow and, on close examination, there are the other (involucral) bracts but no sign of either disc florets, ray florets (petals) or a disc (to which the florets are attached).
My first thoughts were that this is a virus but I can find no reference to a dahlia virus doing this. Most research has been done into DMV (Dahlia Mosaic Virus) which causes mottling of the foliage and general stunting and twisting. I had that last year (well the dahlias here did!). Just because I can’t find any reference to this sort of symptoms of virus infection does not mean this isn’t a virus but it makes me question my first thoughts. The plant seems healthy and shows no mottling on the leaves. However, the stems are rather thin which seems a bit strange.
So the next possibility is that the problem is genetic. While the plant is unable to set seeds it may have been grown from a seed in its present form and it is just a strange genetic freak that would normally die out.
Either way, the little dahlia is a bit of a monster and the problem will not be cured by cultural means so I think it should be put out of its misery.
Unless you know better?