Brown leaf margins on Rudbeckia fulgida

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!

From what I can see in that picture it looks like the plant was scorched from excess heat and/or not enough water. You are correct that Rudbeckia are generally tolerant of hot, dry conditions but that's once they're established and also means not too extreme. A planter on a roof deck in DC in the summer could easily be exposed to temps over 100F from radiant heat on sunny days. Also, unlike a plant that's growing in the ground, the roots are also getting a lot of heat absorbed from all sides of the container. Another thing to consider is the ability of the plant to absorb water... if the plant was purchased in a small container (e.g. "1-gallon" pot) it was likely very root-bound and had roots circling the outside of the container. Unless the outer roots are gently separated/broken up a bit, the plant may not readily expand its root system into the new soil, so most of its root system remains confined to the original volume which may become quickly dehydrated even if the surrounding new soil is moist.

So, gently dig into the soil in the planter to see if there is any significant new root growth. If not, consider trying to salvage the plant using your hands to break up the old pot-bound roots a bit. Or just pull it out and replant with some heat-tolerant annuals and try again next year.

Lastly... if you did break up the roots when planting, and it's been consistently watered and not exposed to excessive sun and heat, the only other thing I can think of is maybe over-fertilization... like using a "self-feeding" planting mix that includes fert and then adding more fert before the incorporated fert runs out.

Thanks very much for the reply.

I am pretty sure I can rule out it being rootbound. I got it as a very small seedling and completely loosened the roots before planing I also had to transplant in early May, and at that point it seemed like it was well on its way to developing a good root system. Likewise, the only fertilizer it's gotten was what came in the potting mix, so overfertilizing seems like an unlikely culprit also.

Given all of that, some combination of too little water and excessive heat seems like the most likely culprit. I will try being a bit more liberal with the water and see what happens. Two follow-up questions:

* How worried do I need to be about overwatering Rudbeckia?

* Supposing the plant does not improve with more water, is this something that I should expect the plant to cope better with in its second season, or should I consider a different plant for this site?

Thanks you again for your help.