Practically speaking do coffee really effects the growth of plants?

Coffee will act differently depending on the form and concentration with which it is added.

Coffee is acidic so in large amounts it will change your soil pH. Coffee grounds have a pH reading from 3.0 to 5.0 so steady additions will alter the pH of the soil and restrict other nutrients from being available to the plant. Acidic soil locks up solutes the plant needs so coffee grounds work best with acid loving plants OR added to alkaline soil.

Use no more than 1lb/100 sq ft unless on acid loving plants

http://newcrop.hort.purdue.edu/ext/groundsforgarde...

Coffee Grounds N/P/K is 2/0.3/0.2 (This is for dry weight of grounds)

plus they are a minor source of calcium, magnesium & and carbohydrates.

Another way coffee can benefit a plant is by controlling slugs. This effects the growth of a plant indirectly by preventing predation.

Dilute caffeine solutions repel and may kill young slugs. At a concentration of just 0.01%, caffeine sprayed on leaves reduced slugs' feeding by ~1/4. A cup of instant coffee contains about 0.05% caffeine.

http://www.newscientist.com/article/dn2470-caffein...

http://www.hort.wisc.edu/mastergardener/Features/p...

Caffeine, a solute derived from tea leaves or coffee beans, can restrict plant growth

http://www.madsci.org/posts/archives/2000-03/95232...

http://www.newton.dep.anl.gov/askasci/bot00/bot005...

http://www.plantingscience.org/index.php?module=pa...

http://wiki.answers.com/Q/How_does_caffeine_effect...

http://www.chm.bris.ac.uk/webprojects2001/tilling/...

http://www.colostate.edu/Depts/Entomology/courses/...

http://209.85.173.104/search?q=cache:ySCixblN9wwJ:...

/6daysaweek.html

No coffee may not add for good growth of the plants.