Annabelle likes sun and can tolerate quite a bit but, per your description of the symptoms, this plant is getting too much. Yellowed, bleached or whitish leaves suggest that the plant is suffering from sunscald (too much sun, specially hot afternoon sun). I suspect that Annabelle's blooms will brown out too if they are exposed to the hot afternoon sun which means a lot of them would start green but then brown out. The solution to this is to relocate the plant to a more shaded place (wait until the plant is dormant).

Exactly how much sun is the shrub getting, kathieo? Some hydrangeas, especially in the northern states can be grown in full sun, the definition of which is 6 hours or more. While I would not mind planting one in six hours of sun if I could, I would hesitate planting one in 9-10 or more hours of sun. To compare: here in Texas, the leaves bleach if the shrub get sun past 11am or 12pm.

Hope that helps you, kathieo.
Luis

PS - In trying to cover most bases, here is one extra note: yellowed leaves with green veins is a totally different problem called iron chlorosis. I assume this is NOT your problem.

Hi, Kathieo
That's a lot of sun IMHO. Probably 9 hours in mid-summer, right? And did you have the 100 degree weather with a lack of rain in July-Aug? All of that's bad news for hydrangeas.
I have one Annabelle that blooms happily in full shade (small blooms). I have another that gets sun from about 10-2 in midsummer. It's usually a healthy beast, but I was on vacation this past July/Aug when it was hot as Hades with no rain and Annabelle was fried when I got home.
I know zip about iron chlorosis. I just know that Annabelle isn't usually a delicate diva.
I'd move it in early spring if I was you. As soon as you can work the ground, put it where there's less sun. Water the bejeebers out of it every day it doesn't rain for at least 2 weeks. Treat it with one of those fertilizers for transplant shock like QuickStart. If you think it has an iron problem, treat that, too. Maybe it would be a cheaper/easier idea to buy a new one that's not stressed next spring and plant it in a shadier spot.
If you want a hydrangea for your full sun spot, try Limelight. It's full sun in zone 5. It's a late summer bloomer, but that's not all bad. Good luck!
Karen

Ideally it should be located in a part shade area. It is a hardy plant and I've seen in located in full sun locations. However when making comparisons, it seems to thrive in semi shade or part shade locations.

As for the iron chlorosis. I suggest adding bloodmeal to your soil. I would also suggest a compost and composted manure combination once at the start of the season and once towards the end of the season.

Ianna

I would take a few pictures and some of the stems and leaves to your local County Extension Agent. If he or she doesn't know the answer they are set up usually with a University to email questions and can get you answers.
Mary

Thanks everyone for your help. I've decided to try to transplant annabelle in the spring but will give it a boost of compost and composted manure this fall. I have a feeling it was a sick plant when I bought it but I thought it was because it was late in the season and that it would be "all better" the following yr. Oh well, it is worth a try.

If you fertilize it now, this will prevent the plant from going dormant. Just let Annabelle be; keep it well mulched and adequately watered. After a couple of hard frosts, it will be dormant or it will be on its way there. The leaves and the blooms should dry out leaving just the sticks (stems) out there. I would then note when this happened in my calendar and wait an additional two-four weeks to transplant. That gives you an extra margin of safety.

Hydrangeas are not heavy feeders. In the northern states, fertilize once in early June with manure, cottonseed meal or a general purpose slow-release fertilizer. In the southern states, fertilize in May and July. Coffee grounds are ok but stop all fertilizing by August/September.

Luis

A landscaper planted 3 Annabelle hydrangea for me (in mostly shade) in late August. He got them at a reputable nursery that was having an end-of-season sale. Right off the bat, two of the three started to look pretty bad. The leaves are pale (washed out) with brown edges. I figured they were going to check out so I bought another one at a different nursery. It's in good shape and doesn't seem to be bothered by its sick-looking neighbors. Perhaps the pale ones are lacking nitrogen(?). The bed that they're in was improved with some "super loam" (top soil and compost) when they were planted, but perhaps I should have added something else, e.g. a high nitrogen fertilizer? I'm unfamiliar enough with this variety that I could use some wise advice. Thanks, Paula

I think it's likely that the sickly ones were just in pots too long (probably potted and ready to go in the ground last spring) and then experienced transplant shock. Hydrangeas need lots of water. That's probably the best thing you can do for them. Even if you haven't watered them faithfully, do it now until there's a frost. A couple of gallons/day on each plant. Annabelles are tough and my $ says they'll jump out of the ground in the spring. My established Annabelles look pathetic right now. As soon as we get chilly evenings, they're done.

Thanks Karen. I feel better about the situation. I think you're right about their being in the pots too long. I'm also glad to know that Annabelles are hearty. We'll see what happens in the spring. Paula

Hi, very new here, just signed up but I might be able to assist. Annabelle is a rugged plant that can take some harsh treatment in the pruning area. Cut them back to about 10" each year in the Fall. They'll come back nicely. When the flowers (I don't believe these are true flowers) appear cut off about half of them. This will keep them from falling over in the summer. They do need some sun light to avoid becoming leggy but enjoy some shade.

I'm in Michigan. Typically, the Annabelle's (and other plants) left by end of summer in garden nurseries are somewhat neglected and underwatered thus the yellow/brown leaves, etc. That's how my first one looked when I purchased it nine years ago. It was lovely in the shade of the morning but in the afternoon sun and heat it wilted and sometimes leaves turned yellowish. Even extra watering and misting the leaves to cool them wouldn't change things very much. Only after the sun went down and it cooled off did it revive. Now since my maple has grown over the garden Annabelle receives light shade all day and has reached an abundant 6x6 ft. and never wilts. ...HOWEVER, when I purchased 8 more for another part of the garden which has rather sandy soil and receives both shade/sun, I've noticed that those on the shady side with almost no sun are very happy, whereas those few that receive both morning AND afternoon sun are sadly wilting, leaves turning yellow showing green veins, and even the flowerheads wilt, despite a good amount of watering. Even shading temporarily with cardboard in desperation and misting foliage to cool it, still doesn't help much. Personally, I think they hate the heat. My thinking is if it's too hot (80 degrees) for me, it's too hot for them. Do you think I should fertilize this new garden with Miracle Grow for evergreens (do they like acidic soil??) or just some organic cedar mulch and manure? Any suggestions? Thank you so much! Jeanne

Jeanne...I gave my Annabelle miracle grow for acid loving plants. I did transplant it this past spring and it is doing beautifully. It is now in a spot in my perennial bed, in the background where it gets AM sun and some aftenoon sun, but then it is in the shade the rest of the day. I watered it well when I transplanted it and keep it moist if we get no rain. So far, so good. I am so glad I transplanted it. Apparently it was getting too much heat from those darn boulders it was in front of. So you are right on that point. good luck with yours..Kathie