I have alkaline soil. I have read that blueberries, three years old, and now the Hostas I have just planted prefer acidic soil. I purchased a bag of powdered sulfer. Can I just scatter that around my plants to add acidity?
Soil Conditioning for Blueberries and Hostas
Certified GKH Gardening Expert
Sulfer is a decent way to lower soil pH, though it's pretty slow-acting, especially if the plants are already established. Ideally you'd be able to work it into the soil, but since the roots are in the way, you'll want to scatter it just like you said. Applications should be no more than 2 lbs per 100 square feet (about 1 kg/9 square meters), so get an idea of how much area you'll be covering and adjust accordingly.
Sulfur isn't the only way to lower pH. You can read about some other methods here: https://www.gardeningknowhow.com/garden-how-to/soil-fertilizers/raise-acid-level-soil.htm
And here: https://www.gardeningknowhow.com/edible/fruits/blueberries/lower-soil-ph-blueberries.htm
You may also want to get a soil test so you have some idea of where you pH stands to begin with.