I got to know coffee grounds are added to the soil to make it acidic. So started using it for my blueberry plant.

What plants should I avoid coffee grounds even if that plant requires acidic soil

Coffee grounds help make good rich soil but do little to nothing to a soils PH.

Once they are ground and cooked they are neutral - neither alkaline nor acid. They are good mixed into the soil. Here are several testers inserted into pure coffee grounds:

I used to get free coffee ground from Starbucks, I put them on my tomato plants.

Good idea. Always mix them into the soil or they can form a crust preventing effective watering.

What exactly are the benefits of coffee grounds mixed into soil?

They improve the tilth of the soil.
https://www.britannica.com/sci...

Thank you Arlene. I read more about coffee grounds and how they actually affect the soil.

SoCalGardenNut said:I used to get free coffee ground from Starbucks, I put them on my tomato plants.

I went to Starbucks several times and they never had any used coffee ground. The manager always said "come back later, we may have some in the afternoon." I always came back 3 or 4 hours later (around 6 p.m.) and they still didn't have any.

Do you have any idea when they dump their used coffee ground?

Years ago there was a guy on a Palm forum I belong to who was experimenting using coffee grounds as a pesticide/prevention for scale on palms. He had done a lot of research on it and said that coffee contains over a 100 components that no one is exactly sure what they do. But he did have some success with it

@Kimmy2012 - my guess is they have a deal somewhere and you'll never get grounds from them. You may want to try a local coffee shop.

Kimmy2012 said:

I went to Starbucks several times and they never had any used coffee ground. The manager always said "come back later, we may have some in the afternoon." I always came back 3 or 4 hours later (around 6 p.m.) and they still didn't have any.

Do you have any idea when they dump their used coffee ground?

I did this about 10-15 years ago, not sure what they do now.

I use coffee grounds on my blueberry bed but I also use a Soil Acidifier and bone meal fertilizer.
I can't remember the name of the acidification but it's in the picture attached. I haven't had much luck with the PH analyses like the one that you stick in the soil like Pirl above, but his looks more sophisticated than the ones that I've tried. I bought a soil test kit two years ago, but that's difficult to use too.

Soil acidifier will do much more for your blueberry than coffee grounds.

Starbucks used to be a great place for used coffee grounds. Now it seems that they can't be bothered to save them. I've spoken to most in my area. Most of that group specifically told me they won't save them. The few that did, it wasn't much and made the stops like playing shot machines. They just said they were busy. I got lucky a few years with two. Staff changed and now they have dried up as well. My local coffee shops and doughnut places either won't save them, or have someone picking up all of what they save. So... I'm still looking. Good luck in your search.