I have some of those in my garden, usually on roses or other plants which are in direct hot sun during heat waves, and which either could not stand the heat, or did not have enough water (so far I have only seen this right after really unusual hot spells, in plants in pots). So, I would agree with your guess, and you could call it sunburn. My Le Vesuve did not get this, but it is in the ground.

Jackie

It looks like mine do when sunburned. Is the left side of Le Vesuve facing west, or southwest? Lisa

Perhaps a bit of salt build-up, too. Have you fertilized them in the past month?

All of these plants are in the ground and none of them have been fertilized for well over a year. Le Vesuve and Aunt Margy's Rose are already in the shade by mid afternoon.

Not enough water for the temperature conditions, maybe add some more mulch, and more water if possible.

they will recover, especially if the weather cools off, and they get a bit of TLC.

best

claire

I get this too, Ingrid. All those pictures are happening here too. I think some of the roses could improve when more established. I also had some do this that theoretically had enough water, but the heat was too much. I'm planning on planting some pots earlier than planned, because they can't stand the heat either. I think a shade cloth/structure could have helped here, but too late now since the damage is done.

At this time of the year the only roses that have "normal" foliage are those that have only morning sun; every other rose has its share of ugly leaves. What we really need is a prolonged summer rain to relieve the stress of constant heat radiation, but I'm not counting on that in this year that is predicted to have a la nina winter.

That's what it looks like on many roses in my garden (including my young-ish Souvenir de la Malmaison) this time of year. In my soil, it's a bit of salt buildup, inherent in the soil, plus the recent extreme heat. The older roses, those in the best spots, and the more resilient types handle these conditions better and don't show as much of that kind of damage, but others look less than optimum. It's transitory and happens year after year in this garden -- everybody survives and has improved looks in fall. In fact, some of the less attractive plants are already putting on nicer growth, after the past cooler week or two.

The looks of leaves having received long term hard water irrigation in hot conditions. Very familiar to me at this time of year.

OT: I sent you a message yesterday, Ingrid. It came back as unable to be delivered. I'm not sure why. Lisa

If you suspect salt buildup, you may be interested in this scientific paper:

http://forums2.gardenweb.com/discussions/4813074/new-silicon-salt-stress-rose-research-paper

I suspect that Nik has put the whole problem very succinctly, and it completely fits my conditions. What's really needed is rain, which I doubt we'll have any time soon.

Lisa, please contact me at g_g_g@netzero.net. The houzz system is not user-friendly, and frustrating to deal with.

Salt buildup due to hard water irrigation (especially when dripped) can be partly alleviated by repeatedly and thoroughly flushing the root area (using the same water, of course). If you can spare the water it is worth it. Some nitrogen fert will be required afterwards.