This happens to my hydrangeas every year. I use liquid soil acidifier that has iron in it and it seems to help. However, I don't know if the other plants you mentioned like acidic soil or not.

I am not a master gardener and have no training in horticulture except what I've taken from books, magazines and the internet, so someone else might know a better solution.

Does this happen every year or is it a new thing?

Is your weather normal, hot, rainy,...?

What have you added in terms of amendments, mulches and fertilizers?

It's normal to see this, but not to this degree. This year seems worse, or maybe I just have more plants that are showing the problem.

The halesia (silverbell) has struggled since I planted it. The rest have grown nicely, but still have the yellowed leaves each year. Just, as I said, it seems really bad at the moment.

I'd say it might be something in my tap water, because most of what is showing problems receives supplementary water due to either being a waterhog (the hydrangea) or newly planted (the itea and the lindera), except that I've only given the oxedendrum and the halesia supplementary water once or twice this summer. Some of these plants have shown the yellowing throughout the growing season - for instance the itea has shown it since April-ish.

I don't typically give any fertiliser to my plants. I mulch using pinestraw - it's free and readily available with all the loblollies I have around and occasionally I'll pick up a bag of compost and throw some of that at the base of my plants. I often toss vegetable scraps beneath the pinestraw at the hydrangea's feet.

The weather seems normal. It's hot, humid, and rain has been fairly reliable except for two weeks in June and the last week of July. Last year was bad weatherwise with only three rains from the beginning of June until the end of September when the floods happened. (We were lucky and the water did not enter our house - stopped short of about .5cm from getting in. Phew.)

For what it's worth, the hydrangea flowered pink when I planted it, and has gradually changed to purple and is now heading towards blue, but some pink flowerheads still showed up.

Plant chlorosis, yellowing of a plants leaves due to lack of chlorophyll, has many causes although the usual cause is thought to be soil pH. Before trying anything to try to correct this wait for your soil test.

Perhaps this article on plant chlorosis may be of some help.

http://extension.illinois.edu/focus/index.cfm?problem=chlorosis

kimmq is kimmsr