Hydrangeas do best in well draining, acidic soil. In places where the soil is alkaline, the roots are unable to absorb iron from the soil and the leaves turn light green or yellowish, except for the leaf veins which remain dark green. To make the soil more acidic, the soil must be regularly amended using products such as liquid iron-chelated compounds, garden Sulphur, green sand, iron sulfate or aluminum sulfate. Liquid amendments will correct the problem faster than solids/granular ones and can be administered when you are planning to water as they have to be diluted in water per the label directions. But neither is "fast" so do not expect the leaves to correct overnight; give them several weeks of slow and gradual improvement. Either type of product though, must be re-applied per label directions in order to maintain the soil acidity changes.

There are soil pH kits sold at many plant nurseries that can help you determine how the soil is doing. They are not exact measurements but "close enough to government work" as they say. You mix water, a soil sample and a pill. Shake the solution and wait. After a while, the pill makes the soil turn a certain color that indicates whether the soil is very acidic, acidic, neutral, alkaline, etc.

You need to keep amending the soil regularly because the soil tends to revert back to its "normal" state if you quit. I suggest starting with one application now and additional ones based on the frequency suggested by the product that you choose. Up here in the DFW Metroplex, I amend in the spring and sometimes, again in the late summer months or early Fall months.

One other thing to keep is mind is the amount of rain one gets. A lot of rain can temporarily make the leaves chlorotic but if the problem does not self correct then you need to amend the soil. In your case, since you said it has been this way for a while, I would start regularly amending the soil now.

Does that help you?
Luis

Yes , thanks. Will get liquid amendment. My soil has been tested as neutral and it has been amended to be more acid as I grow azaleas in that bed also.

Note: azaleas and rhododendrons do not like large amounts of aluminum sulfate because it is toxic to them. If you ever have to use a/s, keep it away from the azaleas. A little amount will not cause any obvious damage.

hey you were right, I applied ES and within 48 hrs it had greened up, Plus it has 2 flowers, woohoo!

All right! Keep an eye on your plant during July-September to see if the soil needs to be amended again.

Bossyvossy, what is "ES"? I went back through Luis' postings but I don't see anything that fits that acronym. I think I need to amend my soil, too, so I would appreciate the help.

Thanks!
Carol