Best to have your soil tested first. It depends on the type of Al present - few plants will tolerate levels of soluble aluminum (Al+++) above 1.0ppm and most will be affected by .5ppm. But it also depends a great deal on soil pH, soil texture and the amount of organic matter present. The only way you will know for sure if potential aluminum toxicity is present is to have your soil tested by a proper lab.

I wouldn't worry about one application of aluminum sulfate....there's many gardens out there with hydrangeas that have been fed this chemical in hopes of turning a pink flower blue to change the pH over a season.
Aluminum sulfate can cause aluminum build-up in the soil OVER A LONG TERM....hence the reason to trust garden sulfur instead. Like sulfur, the aluminum has to be used soon enough to make an impression on the plant roots.
If you have stopped using the aluminum sulfate then the aluminum will work its way out.
Don't go off half-kokked trying to fix a problem that isn't there by adding lime to raise the Ph.

Australia did that...they had problems with animals and brougt in animals to take care of that, then found they had a bigger problem so they brought in more animals, which ended up with a bigger problem....

you get the idea. Let nature takes its course.

Ummmmm.....there's a BIG difference in the rate of application with aluminum sufate to encourage blue flowers on a hydrangea and the 2kg applied to just over 100sf. And aluminum sulfate is almost fully soluble, which means it can pose immediate toxicity to vulnerable plants if over-applied. How long it may be present in the soil depends as well on the existing pH before application and the soil type. Naturally acidic soils and those that are mostly clay and/or with a high level of organic matter could pose problems.

Again, the only way you will know for sure if your soil does not contain too high a level of Al+++ for most plants is to have it tested. Otherwise, you are just guessing and can put other new plantings at risk.

"I wouldn't worry about one application of aluminum sulfate....there's many gardens out there with hydrangeas that have been fed this chemical in hopes of turning a pink flower blue to change the pH over a season. "

That would be a valid point if those people were eating their hydrangeas.

this was a one time thing. The soil is sandy and ph was neutral prior to aluminum application. Soil has healthy levels of OM.

In one area of the garden where I put a lot of manure into the soil.....I had it tested and the aluminum came back at 302 ppm. Hasen't harmed nothing, tomatoes, apple fruit are good.

You want to be sure you test for soluble aluminum (Al+++), which is not commonly done with most soil tests - thet tend only to measure overall Al levels, which are not at all the same thing. Aluminum is a very common element and all soils tend to have it present but most is not soluble and is unavailable. Large applications of aluminum sulfate can have a much different impact. In fact, if you read up on applying aluminum sulfate to blue up hydrangeas, you will find numerous cautions against overapplying this product, leading to aluminum toxicity.