The day I tested that 'coffee grounds in the garden' tip and killed my hydrangeas
I read this article last month saying used coffee grounds add nitrogen and make soil acidic. So I dumped about 2 cups around each of my 3 hydrangeas in Portland. Within a week the leaves turned yellow and started curling. Turns out fresh grounds are still acidic enough to burn roots. I found a soil test kit at Home Depot for $12 and my pH was down to 4.5. Anyone else kill a plant trying to be eco-friendly?
Hold on, I gotta push back a little here. You dumped 2 cups of fresh grounds around each plant, that's a ton of nitrogen all at once, of course it burned them. I use coffee grounds all the time in my garden but only a thin layer mixed into compost or let them dry out first for a few weeks. Plus hydrangeas actually want a slightly acidic soil around 5.5-6.0 for that blue color, not 4.5. The tip isn't wrong, you just went way overboard with the amount and skipped the simple step of letting them break down first.
Piling on fresh grounds like that is a rough lesson, @kai_burns73. Ive done the same thing with compost and learned the hard way that a little patience goes a long way.