Caffeine in compost
Greetiings Earth People. You mention in the article on adding coffee grounds to compost and germinating lettuce that lettuce did not germinate well and was stunted compared to that germinated in potting soil. I have read elsewhere on the net that this could be due to the effects of caffeine on germinating seeds and seedlings. If true, this may constitute reason NOT to use coffee grounds. I have used big bags of grounds from Starbucks in my composting bins with leaves. While I have not noticed problems, I am concerned now about this issue. I seek guidance from your Big Giant Brain. Rob Sambosky
St. Joseph County Indiana
I'm not sure sure which article to which you are referring but Rosie wrote this one over a decade ago: https://www.agriculture.purdue.edu/agcomm/newscolumns/archives/YGnews/2006/February/060216YG.htm
It's an oldie but a goodie and the advice still stands. I think that you are right in being wary with seedlings, partly because I don't know which seedlings you are growing. Relatively speaking, it is fairly high in nitrogen and other salts as an amendment. As the article alludes, it is best used as an amendment for perennials, especially those that may need to lower the pH and as a compost ingredient to diffuse some of its more potent properties but enriching the compost overall.
Have a great day. I'm enjoying my own cup of joe as I type!