There are many folk-cures and hear-say remedies for growing plants, many if not most will end in weakening if not killing the plant, the best recourse is to know the plant, know what type of soil it likes, and what kind of nutrients it requires, (well balanced nutrient filled diet) the simple course of action would be: Plain water, Air, Sunlight [full/partial/defused] and a mild form of fertilizer, keeping in mind not to over water or under water.
Caffeine is produced by some plants in order to ward off predators (it is a toxin that is harmful to a number of animals and insects). The caffeine produced by plants does not help them to grow.
There is no real benefit gained from "feeding" caffiene to plants. Years ago, people used to mulch their spent coffee grounds into the soil around plants. Since the grounds don't have much nutritional value, this isn't done too much anymore.
Actually Caffeine does help grow plants. i did the esperiment and it worked althought it is moch better if you use pure liquid caffeine, the resuts will improve and he plant will grow about double its size!
Answer C: I recently did an experiment on this, and found the opposite of the outcome described in answer B. I used NoDoz pills (200 mg of caffeine each) and ground 4 in a bag, then added to half a cup of water, and fed to grass seed. They actually grew two times SLOWER. Maybe caffeine in moderation is fine, but an overdose can harm plants?
Answer D: Answer B is a troll. Caffeine harms plant growth. I have done an experiment about it.
Coffee grounds can be used to help lower the ph of soil. This is helpful when growing acid loving plants like blueberries and azaleas. It can also be used to change the color of hydrangeas blue. It is also used by many fishermen to attract earthworms.