Hello, viviank. That sounds like too often of a quick acting fertilizer to me. Apply instead some manure or chemical fertilizer twice a year, in May and June. Regarding chemical fertilizers, any slow release fertilizer with a balanced NPK ratio (e.g., 10-10-10, etc) will be fine.

The website below gives some pretty good information. Check it out.

Luis

Here is a link that might be useful: Fertilizing Hydrangeas

I am wondering about the same thing too. I read that Holly Tone (4-6-4) was supposed to be good for those who wanted blue ES hydrangeas too, and it was recommended that applications be made in April, May and July. I wonder if anyone has had experience with the use of Holly Tone for hydrangeas please?

It is a very good product for acid loving plants like hydrangeas, gardenias, azaleas, rhodies. It contains dehydrated manure and several organic meals. That makes it a slow release fertilizer. If it were available in my area, I would apply it in May and June on my hydrangeas. But they do not sell it. I do not understand why but local Espoma dealers always sell other Espoma Products here. Oh, welllll.... Luis

I forgot to say one more thing in case this applies to you.

Some people feed aluminum sulfate to hydrangeas in order to change the color of the flowers from pink to blue but, Hollytone contains ammonium sulfate instead of aluminum sulfate. If you are one of the persons doing this, you need to separately add aluminum sulfate because Hollytone will not provide that mineral (aluminum).

Also, while the aluminum part of the compound helps with the change of color in hydrangeas, also be aware that it is toxic to azaleas/rhodies.

Just a little FYI,
Luis

When is a good time to add aluminum sulfate to my new ES? I still don't know what color it is yet, it still looks green/white right now.

If the buds are already forming, its too late to change the color of those.

This year, I began adding aluminum sulphate and Mir-Acid as soon as my plants broke dormancy. I tilled in a bunch of peat moss and compost aroudd the base of my ES, scratched in some Aluminum Sulphate around the plant, and then I've also given it AS dissolved in water a few times since. Be sure to keep the Aluminum Sulphate off the foliage, or you will burn it. I've also been lowering the pH of my water a bit before watering also.

If I still don't get blue flowers this summer on my ES, then I'll try adding some sulfur to the soil to lower the pH a bit, in addition to the other things mentioned above.

If that doesn't work, I'm giving up. :)

Thanks Matt, how do you lower the pH of your water? And do you do that everytime you water the hydrangea?

I use a sulfuric acid (35%) solution added to my water. Some pH loweing products use phosphoric acid to lower the pH, but you don't want to add any phosphoros if you are trying to get blue blooms on your hydrangeas. Phosphorus inhibits the plant's uptake of aluminum. (which causes blue flowers), so if your trying for blue blooms, you don't want to add extra phosphorus to the water/soil. The best water acidifier (lower pH) when growing blue hydrangeas is sulfuric acid, if your trying for pink flowers, then phosphoric acid is best. Both products will effectively lower the pH of your water, but one promotes blue blooms, one promotes pink blooms. So just be sure to use the right one for your application.

Yes, I lower the pH of my water each time I water my ES.

Also, while the aluminum part of the compound helps with the change of color in hydrangeas, also be aware that it is toxic to azaleas/rhodies"

Is this statement true from Louis?

On the Aluminum Sulphate label it specifically says for use with Azales

Here is a link that might be useful: Click this link for label

From the American Rhododendron Society (rosebay) website:
"Never use aluminum sulfate to increase soil acidity as it is toxic to many plants including rhododendrons. This is a most important point! Under no circumstances should you use aluminum sulfate (Al2SO4) around your rhododendrons. As was pointed out in a previous article, soluble aluminum is toxic to rhododendrons. The chemical, aluminum sulfate, is soluble in water thus the aluminum component is immediately available  and toxic - to the plants. As the pH level of the soil decreases, the aluminum component becomes increasingly soluble  and thus increasingly toxic. Therefore, although aluminum sulfate will certainly reduce the soil acidity, it can, and will, quickly injure and may even kill your rhododendrons. Even though the plants may tolerate small quantities of this material, why should any quantity of a toxic material be added to the soil when other perfectly safe materials such as sulfur are available?"

And since azaleas are just a varietal form of rhododendron, the same concerns apply to them as well. So yes, Luis' comment is entirely accurate.

How can they explicitly say for use on Rhoodendrons then. Did you click the the link? (what a bunch of crap they market it with actual name of plant on the label) So is it fair to say that Aluminum Sulfate should only be used on Endless Summers to change flowers to blue? Also what if they have already started to bloom? Will the flowers still take on any blue color, right now their a mix bewteen white/blue.

Whats the verdict on Miracid, can this be applied to Rhodoendron's?

I'm interested in anything to help acidify my watering. Where do you get your sulfuric acid and how do you apply it? In my region there's a lot of underlying limestone and watering can be a problem because of that. I know of two nurseries around here that have some kind of an inline system to add acidity, but I figured that'd be too costly for me.

I've heard about watering with vinegar added, but I've never had anyone tell me just how much and how often. And I'm a little troubled by the thought of how attractive the smell of vinegar might be to some marauding critter out some night.

Hay

Oh no!!!!!!!
I wish I had read this 3 days ago.......I just added aluminum sulphate all around my rhodos when I treated by hydrangeas. I read the box carefully and it recommended it for rhodos, ugh. The nursery I bought them from also suggested it to me when I bought the rhodos.
What if anything can I do now to "fix" what I've done? I will be so upset if I killed my rhodos. I was doing pretty well for a "newbie" I will post this question on the rhodo forum as well.

My ES had no blooms last summer. About mid June I read I should add mir-acid about every three weeks to ensure blue blooms. I started and re-stared again this spring. I now have a dozen or so bloom getting ready, but it appears they will all be pink.

Response to the question on removing aluminum sulphate from the soil. You might have some luck if you can get your hands on some gympsum and water very well to try to flush the soil. I read on a website about 30 reasons to use gypsum and one mentioned it prevents soil toxicity found in micro nutrients. It did not specifically say aluminum but if you have no other options I'd use that.

my question too; where to get sulphuric acid in Ontario and how to apply it too?