Ask-a-Dave's-Gardener: Brown leaf margins on Rudbeckia fulgida , 1 by DCNovice

DCNovice wrote:
This spring, I planted some Rudbeckia in a trough planter on a roof deck in Washington, DC. It has generally done well and has begun flowering, but recently many of the leaves have begun to brown around the edges (see picture). I am trying to figure out what is going on.

One theory is that it\'s not getting enough water. But I have been checking the soil daily and watering when the two couple of inches of soil seem dry. I am new at this, so perhaps I am misjudging what is \"dry enough\" and underwatering as a result, but I would be a bit surprised.

The other possibility is that the sun, wind, and heat up on the deck are taking their toll. But I thought Rudbeckia was supposed to pretty tolerant of this sort of thing, so that also seems like an unlikely explanation.

So I am a bit stumped, and I would greatly appreciate any advice anyone might have. Of course, if additional information/photos/etc. would be useful, I would be more than happy to provide it.

Thanks very much for reading!